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tonyowen
9-Feb-2019, 07:22
The distance between the lens front and film plane can be noticeably greater with LF cameras than with 35mm cameras.
Therefore is it necessary to take into account this extra distance when using a standard electronic flash on a LF camera?

To clarify, with 35mm the flash's GN = aperture x distance; where distance can be direct or bounced.
Therefore, with LF does the GN = aperture x (flash to object distance (bounced or direct] + distance from lens front to film plane)????

Or conversely is there a correction factor for the light loss due to increased optical path in LF versus 35mm camera????

regards

Tony

Jim Noel
9-Feb-2019, 07:50
No it doesn't and there isn't.

Charles S
9-Feb-2019, 08:18
Look up bellows factor for this topic. The light source doesn't matter

BrianShaw
9-Feb-2019, 08:27
Do the arithmetic... in many cases any “additional distance” between the lens and film planes will be rather insignificant (in practical terms) in the GN formula.

What is your photographic scenario... normal “average “ pictures, close-up portraits, or strobe-illuminated extreme macro work?

The metric for when bellows extension might be worth considering is deviation from “normal infinity” bellows draw, not the difference based on camera format.

ic-racer
9-Feb-2019, 08:45
1) Unless there is smoke or other optically dense gas in the camera, light rays will not diminish in intensity along their path through any camera.

2) The flash-to-subject distance equation for exposure does not have a "camera position" component in it.

tonyowen
9-Feb-2019, 09:06
Do the arithmetic... in many cases any “additional distance” between the lens and film planes will be rather insignificant (in practical terms) in the GN formula..

Unless there is smoke or other optically dense gas in the camera, light rays will not diminish in intensity along their path through any camera..

Agreed with both of you. But I'm trying to understand why my electronic flash guns do not expose paper negatives in my LF camera.
The flash guns have GNs of 30 & 46 (metric @ ISO100) I've corrected those values to suit ISO6 and have checked and tripled checked lens speed, aperture, pc-cable, lens filter [not being red], distance to object, dark slide out, lens cocked etc etc but all I get is unexposed sheets irrespective of which flash gun I use.

regards
Tony

Charles S
9-Feb-2019, 09:27
Agreed with both of you. But I'm trying to understand why my electronic flash guns do not expose paper negatives in my LF camera.
The flash guns have GNs of 30 & 46 (metric @ ISO100) I've corrected those values to suit ISO6 and have checked and tripled checked lens speed, aperture, pc-cable, lens filter [not being red], distance to object, dark slide out, lens cocked etc etc but all I get is unexposed sheets irrespective of which flash gun I use.

regards
Tony

That sounds like a sync issue. Which kind of shutter do you use ?

BrianShaw
9-Feb-2019, 09:32
Oh... paper neg????

Bob Salomon
9-Feb-2019, 09:59
Agreed with both of you. But I'm trying to understand why my electronic flash guns do not expose paper negatives in my LF camera.
The flash guns have GNs of 30 & 46 (metric @ ISO100) I've corrected those values to suit ISO6 and have checked and tripled checked lens speed, aperture, pc-cable, lens filter [not being red], distance to object, dark slide out, lens cocked etc etc but all I get is unexposed sheets irrespective of which flash gun I use.

regards
Tony

Plug in your flash, remove the camera’s gg. Point the flash and the camera at a wall. Look through the back and fire the shutter. You should see a full circle of bright light in the shutter when the flash fires. Do you? Then your shutter is properly synched for your flash. If you don’t make sure if your shutter has an M/X lever it is set at X and try again. If not the you need an X synch shutter or your shutter needs service!

cowanw
9-Feb-2019, 10:58
What would a typical flash to subject distance be? and at what f stop would you shoot please?

tonyowen
9-Feb-2019, 13:17
What would a typical flash to subject distance be? and at what f stop would you shoot please?
The corrected GNs are 7.5 and 11.5 so the distances for the aperture son my lens are between 0.86m and 2.45m - see below
6ISO GN7.5=f4.7@1.60m or GN11.5 = f4.7@2.45m.
6ISO GN7.5=f5.6@1.34m or GN11.5 = f5.6@2.05m.
6ISO GN7.5=f8@1.00m or GN11.5 = f8@1.44m.
6ISO GN7.5=f11@0.68m or GN11.5 = f11@1.05m.

regards
Tony

tonyowen
9-Feb-2019, 13:20
If you don’t make sure if your shutter has an M/X lever it is set at X and try again. If not the you need an X synch shutter or your shutter needs service!

MXV shutter recently serviced 'x' contact is synch'd - Shutter set at 'x' by default.
regards
Tony

Jac@stafford.net
9-Feb-2019, 13:55
In my modest experience paper does not respond the same to electronic flash as film does. I look forward to someone smarter who me can correct my opinion.

cowanw
9-Feb-2019, 14:39
The corrected GNs are 7.5 and 11.5 so the distances for the aperture son my lens are between 0.86m and 2.45m - see below
6ISO GN7.5=f4.7@1.60m or GN11.5 = f4.7@2.45m.
6ISO GN7.5=f5.6@1.34m or GN11.5 = f5.6@2.05m.
6ISO GN7.5=f8@1.00m or GN11.5 = f8@1.44m.
6ISO GN7.5=f11@0.68m or GN11.5 = f11@1.05m.

regards
Tony

Just the way you said that; that is .86 m to 2.45 m flash to subject, not subject to aperture, right?
Bounce can take up an extra stop depending on the ceiling.

tonyowen
10-Feb-2019, 02:06
Just the way you said that; that is .86 m to 2.45 m flash to subject, not subject to aperture, right?
Bounce can take up an extra stop depending on the ceiling.

Aperture is given in the 'table' from f4.7 to f11. The distance range is from f11 with a [corrected] GN of 7.5 to f4.7 with a [corrected] GN of 11.5
Direct no bounce
regards
Tony

tonyowen
10-Feb-2019, 02:21
In my modest experience paper does not respond the same to electronic flash as film does. I look forward to someone smarter who me can correct my opinion.
Agreed - my flash guns and LF camera work with film (Fomapan 100) without problem.
Also electronic flash is used by others to 'pre-flash' paper negatives.

This is why I'm trying to determine the factors that [might/are/could] preclude my use of electronic flash with paper negatives

regards
Tony

Pere Casals
10-Feb-2019, 03:46
GN = aperture x (flash to object distance (bounced or direct] + distance from lens front to film plane)????

Tony, here you have conceptual issue.

With flashes and GN, the distance from camera to subject is always irrelevant, what is used in de calculation is the distance from flash to the subject, both in 35mm and in LF. In 35mm flash can be not in the camera...

So to apply GN always use flash to subject distance, adding the bounce in the ceiling if it's the case.

What is different in LF is that you have to use the bellows compensation factor, exactly the same factor has to be applied for flash exposure or for (no flash) outdoor shots, for close subjects.

Pere Casals
10-Feb-2019, 03:50
In my modest experience paper does not respond the same to electronic flash as film does. I look forward to someone smarter who me can correct my opinion.

Jac perhaps (speculating) there is a reciprocity failure factor. LIRF may be present both for long exposures but also for extremly short exposures, and a flash can be 1/30,000 , for example.

"Reciprocity also breaks down at extremely high levels of illumination with very short exposures" https://en.wikipedia.org/wiki/Reciprocity_(photography)#Reciprocity_failure

tonyowen
10-Feb-2019, 07:11
Tony, here you have conceptual issue.

With flashes and GN, the distance from camera to subject is always irrelevant, what is used in de calculation is the distance from flash to the subject, both in 35mm and in LF. In 35mm flash can be not in the camera...

So to apply GN always use flash to subject distance, adding the bounce in the ceiling if it's the case.

What is different in LF is that you have to use the bellows compensation factor, exactly the same factor has to be applied for flash exposure or for (no flash) outdoor shots, for close subjects.
QUOTE=Pere Casals;1483086]Jac perhaps (speculating) there is a reciprocity failure factor. LIRF may be present both for long exposures but also for extremly short exposures, and a flash can be 1/30,000 , for example.

"Reciprocity also breaks down at extremely high levels of illumination with very short exposures" https://en.wikipedia.org/wiki/Reciprocity_(photography)#Reciprocity_failure[/QUOTE]

Pere, thanks for comments.
However, though the flash duration is short its intensity is large
Using a 135mm lens at circa 2m [lens/flash to subject] the bellows extension is well below 1.5x focal length
So, I should be able to get some 'exposure' on the paper negative BUT I'm getting absolutely nothing.
Hence my posting and persistent questioning.
regards
Tony

cowanw
10-Feb-2019, 07:24
Can you be putting the paper in the dark slide backwards?

Pere Casals
10-Feb-2019, 07:44
QUOTE=Pere Casals;1483086] So, I should be able to get some 'exposure' on the paper negative BUT I'm getting absolutely nothing.

hmmm.... perhaps the synchronization is wrong. If you set the "M" position then the flash fires 20ms before the shutters opens. Use X position. M position was for antique gear needing to ignite the flash 20ms before exposure to allow the light source to reach peak power before the shutter openned, if not the the light was weak, but in M position a modern flash throws all its power sin (say) 1ms, then shutters delays its aperture 19 milliseconds, and then the shutter opens capturing darkness. So check you have set X position.

Also do this, use darkroom safe lights, always open. Close lights "white" lights in the darkroom, now you see with the safe light...

Open shutter like if you were focusing, fire manually the flash, close shutter, and open lights. In this way you don't relly in sinchronization, so you will have a diagnostic.

I guess you are used to make paper negatives without flash, if not ensure you get good exposures with contiunous light before. Compare the images taken with a DSLR with flash vs continuous to stablish flash exposure.

Tony, this is about making key tests to have a diagnostic about what happens...

tonyowen
10-Feb-2019, 08:37
Can you be putting the paper in the dark slide backwards?

Bill,
Possibly once but not several times - even so should get some 'impression'.

hmmm.... perhaps the synchronization is wrong. Also do this, use darkroom safe lights, always open. Close lights "white" lights in the darkroom, now you see with the safe light... I guess you are used to make paper negatives without flash,...

Pere,
Sunch checked when shutter cla'd last year. Set on 'x' as default.
Have used the flash with 'B' setting and firing via the 'Test' button whilst the shutter was open in a very dark room [I assumed Test means full power]. All to no avail.
Paper negatives exposed in 'daylight' without flash all turned out okay - except when I inadvertently used a red filter!!!!
Both flash guns work okay with film.
All flash exposures done on the 'x' setting - the computer controlled exposure never chosen

Diagnostics infer electronic flash is not compatible with paper negatives in my setup.

Yet in a private message Emil Schildt states "This [paper negative portrait] is actually with the use of flash - with soft box attached - it works really well"

????????????
regards
Tony

Pere Casals
10-Feb-2019, 09:56
????????????

Shot the flash to the paper and develop to see....

cowanw
10-Feb-2019, 10:11
Is your developer good?

Neal Chaves
10-Feb-2019, 15:57
Agreed with both of you. But I'm trying to understand why my electronic flash guns do not expose paper negatives in my LF camera.
The flash guns have GNs of 30 & 46 (metric @ ISO100) I've corrected those values to suit ISO6 and have checked and tripled checked lens speed, aperture, pc-cable, lens filter [not being red], distance to object, dark slide out, lens cocked etc etc but all I get is unexposed sheets irrespective of which flash gun I use.

regards
Tony

I would think you need a lot more flash power, at a minimum 4000WS out of a 5" reflector (150,000 BCPS), giving a guide number of about 350 with that slow emulsion. This is line with what photographers I know are using to expose wet plate with electronic flash. If you want light modifiers, even more power is needed. Your flash guns may not even be reaching the paper's threshold exposure. Try multiple pops and see if you can bring up some tone. See Norman chart below.[187564

Jac@stafford.net
10-Feb-2019, 16:10
Shot the flash to the paper and develop to see....

Excellent fundamental requisite. I look forward to the outcome.

Pfsor
10-Feb-2019, 16:18
Shot the flash to the paper and develop to see....

And do that at different distances from the paper - you will have your answer about the necessary flash power right away.

Pere Casals
10-Feb-2019, 16:20
And do that at different distances from the paper - you will have your answer about the necessary flash power right away.

...or with a stouffer wedge on the paper...

Pfsor
10-Feb-2019, 16:28
...or with a stouffer wedge on the paper...

He could even use just a flash exposure meter, even quicker than meddling with the paper processing.

tonyowen
11-Feb-2019, 03:54
I would think you need a lot more flash power, at a minimum 4000WS out of a 5" reflector (150,000 BCPS), giving a guide number of about 350 with that slow emulsion. Try multiple pops and see if you can bring up some tone.]

Going from your/the nonograph I don't see 150,000 BCPS - more likely a tenth or less than that. However I agree with your prognosis

He could even use just a flash exposure meter, even quicker than meddling with the paper processing.

Unfortunately I do not have a flash exposure meter

I guess I need to do some trials

regards

Tony

Phil Hudson
12-Feb-2019, 01:36
I have been using paper negs in an old passport camera. In the studio I use 3 x 500w flash heads on full power with softbox diffusor screens removed pointing at a subject at a distance of about 1.5 m. It looks about right at f/16. Scaling that back to your scenario I would say that you need lots more light.

tonyowen
12-Feb-2019, 06:22
I have been using paper negs in an old passport camera. In the studio I use 3 x 500w flash heads on full power with softbox diffusor screens removed pointing at a subject at a distance of about 1.5 m. It looks about right at f/16. Scaling that back to your scenario I would say that you need lots more light.

I’ve found a reference that states: As a rough rule of thumb, multiplying the square root of the (wattsecond) Ws number by 4 gives a indicator of the metric GN at ISO 100.

Therefore assuming your shutter is set at 1/60th second and your studio lights give 1500w power

We get 1500 x 0.017 = 25Ws

Therefore GN = SQRT(Ws) x 4 = 20

Both of my flash guns have a higher GN at 100 ISO

However, as stated above this is a rough rule of thumb.
regards
Tony

Bob Salomon
12-Feb-2019, 06:51
I’ve found a reference that states: As a rough rule of thumb, multiplying the square root of the (wattsecond) Ws number by 4 gives a indicator of the metric GN at ISO 100.

Therefore assuming your shutter is set at 1/60th second and your studio lights give 1500w power

We get 1500 x 0.017 = 25Ws

Therefore GN = SQRT(Ws) x 4 = 20

Both of my flash guns have a higher GN at 100 ISO

However, as stated above this is a rough rule of thumb.
regards
Tony

It has to be very rough as watt seconds is not a rating of output.

At any given WS the output will change with reflector size, reflector shape, length of the connecting cable, etc.

Base output on BCPS or ECPS.

Pere Casals
12-Feb-2019, 06:52
... but the paper may be ISO 5 or less, so you may need x20 more flash power in the flash than with TMX.

tonyowen
12-Feb-2019, 07:26
It has to be very rough as watt seconds is not a rating of output.
At any given WS the output will change with reflector size, reflector shape, length of the connecting cable, etc.Base output on BCPS or ECPS.

Agreed, but it surely is some form of indicator even if it is out 10 fold

... but the paper may be ISO 5 or less, so you may need x20 more flash power in the flash than with TMX.

Post #31 refers to 1500w when using paper negatives [ie low ISO] therefore I've assumed apples v apples

regards

Tony

Pere Casals
12-Feb-2019, 08:02
Post #31 refers to 1500w when using paper negatives [ie low ISO] therefore I've assumed apples v apples

yes...

...but I'd take your own exposure working well for ISO 100 film, and I'd multiply x20 the light, around 4 or 5 stops in aperture or light power.

Or easier, use a DSLR, adjust for a good digital shot at ISO 100 and give 5 stops more light.

A DSLR is a perfect flash meter for LF, we only need to understand the relationship in the look. Also I manage to shot the DSLR at the same time than the Norma, so I preview face expresion and if eyes are open.

Not that weird, Hollywood's cinematographers still using film also record video to know if the have the scene. Digital is amazing.

Bob Salomon
12-Feb-2019, 09:18
[QUOTE=tonyowen;1483480]Agreed, but it surely is some form of indicator even if it is out 10 fold

It is no indicator of output at all. It is an indicator of input. And the most efficient flash units are only able to discharge about 80% of their input!

And, since output changes with reflectors, umbrellas, soft boxes, cable length, efficiency of the flash tube, number of connections, etc. watt seconds are the last thing you want to rely on.

Just think, a given unit with say 500 watt seconds will have different outputs with a polished reflector, a matte reflector, an elliptical reflector, an umbrella reflector a snoot, a background reflector or when used bare bulb. But all were 500 WS. How can that WS rating relate to a consistent f stop?

There is no formula to convert a watt second into a f stop without knowing the loading of the capacitors, and no flash manufacturer includes that specification.

On the other hand there are easily found formulas that are accurate that convert a BCPS or an ECPS rating directly into a guide number or f stop.

John Kasaian
12-Feb-2019, 16:30
Now here's an electronic flash worthy of LF photography
The K-17 was, IIRC 9.5" x 9.5
187646
http://invention.si.edu/seeing-dark-aerial-reconnaissance-wwii

Tin Can
12-Feb-2019, 16:38
Very interesting and I love the quote,

“If you don’t wake up at three o’clock in the morning and want to do something,” Edgerton quipped, “why, you’re wasting time.”

tonyowen
13-Feb-2019, 08:39
I ran my tests again and ended up with essentially an unexposed paper negatives.
I’ve listed below what I know and what I DO NOT know.
I know the shutter [cla’d November 2017] was set to 1/60th sec and f4.7. Also the ‘X’ setting chosen
I know the flash [Cobra D650] was set to ‘manual’ with the hood set at 85 degrees to give a GN 46.
I DO NOT know the exact/current GN of the 30+ year old flash.
I positioned the flash and camera about a metre from the subject and the flash fired when the cable release was pressed.
I use a one shot developer [Ilford PQ Universal] in a Jobo 2509 reel.
I DO NOT know how viable/potent the undiluted developer is.
I used Ilford Multigrade paper but DO NOT know the quality of the sheet used.
So back to square one!
Regards
Tony

Bob Salomon
13-Feb-2019, 08:48
I ran my tests again and ended up with essentially an unexposed paper negatives.
I’ve listed below what I know and what I DO NOT know.
I know the shutter [cla’d November 2017] was set to 1/60th sec and f4.7. Also the ‘X’ setting chosen
I know the flash [Cobra D650] was set to ‘manual’ with the hood set at 85 degrees to give a GN 46.
I DO NOT know the exact/current GN of the 30+ year old flash.
I positioned the flash and camera about a metre from the subject and the flash fired when the cable release was pressed.
I use a one shot developer [Ilford PQ Universal] in a Jobo 2509 reel.
I DO NOT know how viable/potent the undiluted developer is.
I used Ilford Multigrade paper but DO NOT know the quality of the sheet used.
So back to square one!
Regards
Tony
GN is easy. What does it say at 3 meters? That’s the GN for whatever ISO you chose.

Dan Fromm
13-Feb-2019, 09:05
Tony, if not specified otherwise the GN is in feet for ISO 100. At three feet -- for this exercise, close enough to 1 m -- with ISO 100 film, the correct aperture if the flash makes its rated output is 46/12 = f/4. Again, close enough to the true value.

Little flashes like the Cobra D650 typically have actual GNs one stop slower than claimed. The only way to be sure is to measure, by shooting a test strip or with a known good flash meter.

Until your flash is proven to make its rated GN, the likely correct aperture with ISO 100 at 1 m is probably f/8. Your paper is approximately six stops slower than ISO 100. Of course you're getting no exposure.

Also, have you verified that on X sync your flash is in fact open when it fires the flash? It should be, but this has to be checked anyway. Remember the strong version of Murphy's law. What can go wrong will go wrong. What can't go wrong will go wrong too.

Bob Salomon
13-Feb-2019, 09:43
Tony, if not specified otherwise the GN is in feet for ISO 100. At three feet -- for this exercise, close enough to 1 m -- with ISO 100 film, the correct aperture if the flash makes its rated output is 46/12 = f/4. Again, close enough to the true value.

Little flashes like the Cobra D650 typically have actual GNs one stop slower than claimed. The only way to be sure is to measure, by shooting a test strip or with a known good flash meter.

Until your flash is proven to make its rated GN, the likely correct aperture with ISO 100 at 1 m is probably f/8. Your paper is approximately six stops slower than ISO 100. Of course you're getting no exposure.

Also, have you verified that on X sync your flash is in fact open when it fires the flash? It should be, but this has to be checked anyway. Remember the strong version of Murphy's law. What can go wrong will go wrong. What can't go wrong will go wrong too.

You also want to know the coverage angle of your flash as these small, cheap units are usually rated in the center of the beam and you may be using more then that.

Dan Fromm
13-Feb-2019, 10:12
Hey Bob, I looked Tony's flash up. If I got it right it is a potato masher and I might have been mistaken in treating its GN as feet, ISO 100. Tony stated a meters GN for it in an early post in this discussion. All that said, what he's getting reeks of massive underexposure.

tonyowen
13-Feb-2019, 12:17
Hey Bob, I looked Tony's flash up. If I got it right it is a potato masher and I might have been mistaken in treating its GN as feet, ISO 100. Tony stated a meters GN for it in an early post in this discussion. All that said, what he's getting reeks of massive underexposure.

Dan,
Potato masher is the correct reference. It is large and [according to the specs] powerful - not quite the big Metz units but getting there.
For information, the GM (metric) is 32 at the 35mm zoom position and 46 at the 85mm zoom position. I calculate the imperial GNs would be 105 & 151 respectively
You refer to a 'good flash meter' but Murphy's Law guarantees the one I get will be 'wrong in some way and how does one prove that the meter is accurate, reliable and consistent!!!

regards
Tony

Tin Can
13-Feb-2019, 12:51
I have proved to myself my flash bulbs, studio flash and modern Nikon flash with DSLR and film.

It all makes sense, then I forget to write it down.

Doing it again soon. :)

I have a Sekonic 758 and it agrees exactly with my Paul C Buff Cyber Commander.

This time it gets printed in large font in seal a meal, actually the heat plastic stuff whatever that's called

and nailed to the studio wall

Dan,
Potato masher is the correct reference. It is large and [according to the specs] powerful - not quite the big Metz units but getting there.
For information, the GM (metric) is 32 at the 35mm zoom position and 46 at the 85mm zoom position. I calculate the imperial GNs would be 105 & 151 respectively
You refer to a 'good flash meter' but Murphy's Law guarantees the one I get will be 'wrong in some way and how does one prove that the meter is accurate, reliable and consistent!!!

regards
Tony

Pfsor
13-Feb-2019, 14:46
I ran my tests again and ended up with essentially an unexposed paper negatives.
I’ve listed below what I know and what I DO NOT know.
I know the shutter [cla’d November 2017] was set to 1/60th sec and f4.7. Also the ‘X’ setting chosen
I know the flash [Cobra D650] was set to ‘manual’ with the hood set at 85 degrees to give a GN 46.
I DO NOT know the exact/current GN of the 30+ year old flash.
I positioned the flash and camera about a metre from the subject and the flash fired when the cable release was pressed.
I use a one shot developer [Ilford PQ Universal] in a Jobo 2509 reel.
I DO NOT know how viable/potent the undiluted developer is.
I used Ilford Multigrade paper but DO NOT know the quality of the sheet used.
So back to square one!
Regards
Tony

If you tried different flash distances from a very close one you would know what the ballpark you're in is. Like this it seems you want to work on this simple problem for months.

David Lobato
13-Feb-2019, 19:16
In my modest experience paper does not respond the same to electronic flash as film does. I look forward to someone smarter who me can correct my opinion.

I know that reciprocity failure occurs with extremely short exposure times, electronic flash being the most common source. With paper designed for seconds and minutes exposure timnes, that may be the case.

tonyowen
14-Feb-2019, 02:09
I have proved to myself my flash bulbs, studio flash and modern Nikon flash with DSLR and film.
It all makes sense, then I forget to write it down. Doing it again soon. :) I have a Sekonic 758 and it agrees exactly with my Paul C Buff Cyber Commander.
This time it gets printed in large font in seal a meal, actually the heat plastic stuff whatever that's called and nailed to the studio wall

If you tried different flash distances from a very close one you would know what the ballpark you're in is. Like this it seems you want to work on this simple problem for months.

I know that reciprocity failure occurs with extremely short exposure times, electronic flash being the most common source. With paper designed for seconds and minutes exposure times, that may be the case.

Randy - mine works with film but not paper. [see bottom response]
Pisor - have tried many distances but all (with paper) fail [see above and below}
David - I've come across that before and it matches my experiences. The quoted flash time for the Cobra's 'manual setting' is 1/1000th sec

regard to all
Tony

Tin Can
14-Feb-2019, 02:34
Tony,

Noted, I only shot 2 paper negs with solar pinhole long ago. I tried Harman Positive with strobes but never liked any result.

I will revisit paper negs soon as I do have a project in mind.

Thanks for the tip!

Pfsor
14-Feb-2019, 03:00
Pisor - have tried many distances but all (with paper) fail [see above and below}

regard to all
Tony

Did you try to flash right into the lens at a close distance? Then you would know if the shutter is correctly synchronised with the flash or not. And you would also see if there is some exposure from the flash on the paper or not.

tonyowen
14-Feb-2019, 03:13
Did you try to flash right into the lens at a close distance? Then you would know if the shutter is correctly synchronised with the flash or not. And you would also see if there is some exposure from the flash on the paper or not.

No I did not - but will try
But did try flash with multi second exposure using B - so synch discounted - again zero 'expsure'
regards
Tony

Pfsor
14-Feb-2019, 03:24
And for a good measure try also to flash a sheet of paper directly out of your camera (in obscurity, of course :)) - you will then have answers to all of your basic questions.

cowanw
14-Feb-2019, 09:20
Also you might pull the dark slide 1 inch, pop the flash, pull another inch, pop again, pull another inch, pop 4 times and so on. Sort of a test strip in camera.

blue4130
14-Feb-2019, 15:33
Have you tried to see if paper will develop at all? Take a sheet of paper that has been exposed to daylight (or develop with all the lights on) does the paper turn black? Is your developer bad?

pepeguitarra
14-Feb-2019, 21:12
Have you tried using another lens with another shutter that has not been messed with?

tonyowen
15-Feb-2019, 01:51
Also you might pull the dark slide 1 inch, pop the flash, pull another inch, pop again, pull another inch, pop 4 times and so on. Sort of a test strip in camera.
I have not, but does not seem appropriate for need - ie I would not use multi-pop for exposure.

Have you tried to see if paper will develop at all? Take a sheet of paper that has been exposed to daylight (or develop with all the lights on) does the paper turn black? Is your developer bad?
Paper develops with daylight exposures

Have you tried using another lens with another shutter that has not been messed with?
Yes, have used 'shutterless' lens with same effect.

>>>>>>>>

I'm presently doing tests where the flash is used directly into the lens, flash is directed at opened DDS, flash used with shutter on Bulb, and a daylight exposure. All from one sheet of 8x10 paper all developed in same tank at same time - will notify results

regards
Tony

cowanw
15-Feb-2019, 16:59
I have not, but does not seem appropriate for need - ie I would not use multi-pop for exposure.
regards
Tony

Fair enough but I was aiming at understanding what sort of flash exposure might give you an image.

tonyowen
16-Feb-2019, 04:00
RESULTS OF TEST - AMBIGUOUS
One sheet of 8x10 Ilford Multigrade paper cut to suit four 4x5 DDS
Paper rated at ISO 6
All tests done with xenar f4.7 135mm lens fitted to camera
All four sheets developed in same JOBO 2500 tank with 2509 reel at same time using Ilford PQ Universal developer for 1 ½ m – developer slightly oxidized see colour in attachment
1] One sheet exposed in daylight @ 1/8th second f5.6 [Weston Master V reflective 10.5]
RESULT: - OKAY – BUT OVEREXPOSED?????
1a] Subsequent shot [10 minutes later] with Nikon Coolpix 8800 gave EXIF info of 1/115s @ f5 @ ISO 50 [This image flipped to orientation of above paper negative]
1b] Coolpix image in b&w
2] One sheet exposed in camera with shutter set to Bulb & f4.7 and Cobra flash at manual and 85mm setting {ie GN46]
RESULT: - DETAILS PARTIALLY VISIBLE
3] One sheet exposed @ 1/60th second, f4.7 [in camera] with Cobra flash at manual and 85mm setting {ie GN46] with flash facing the lens. Flash circa 0.2m (length of pc cable] in front of lens
RESULT: - TOTALLY OVER EXPOSED – WITH ‘BURN’ SPOT SAME SHAPE AS FLASH HEAD
4] One sheet exposed @ 1/60th second, f4.7 [out of camera with slide removed from DDS] with Cobra flash at manual and 85mm setting {ie GN46]. Flash circa 0.7 from open DDS.
RESULT: - TOTALLY OVER EXPOSED
187803 187804 187805 187806

Can only attach 4 images see next post for remaining images
regard
Tony

tonyowen
16-Feb-2019, 04:02
remaining images
187807 187808 187809

regards
Tony

tonyowen
18-Feb-2019, 04:15
three days on and no response????????

regards

Tony

Pere Casals
18-Feb-2019, 05:06
It was not clear you were asking something.

My view is that you have solved it.

Just you need to make some bracketings to find the right ISO reference for metering.

tonyowen
18-Feb-2019, 05:57
It was not clear you were asking something. My view is that you have solved it. Just you need to make some bracketings to find the right ISO reference for metering.

Thanks Pere
My original query was the use of electronic flash with paper negatives.
From my 'test' I guess that it does not work - there 'appears' to be a loss in the subject's reflective image to fp distance. In other words paper negative exposed directly to the flash as in the last image is too great, but in-camera paper exposed to flash via the camera's optical path is not exposed enough.
With the image taken with the bulb setting I wonder how much of the recorded image is to do with the several seconds of exposure rather than the output of the flash gun.
Your comment regarding the correct ISO is I assume is to do with the daylight exposure image??

regards
Tony

Tin Can
18-Feb-2019, 06:00
To explore an answer we need to do our testing

Maybe later in the week I have time

Pere Casals
18-Feb-2019, 06:30
Your comment regarding the correct ISO is I assume is to do with the daylight exposure image??

Tony, here you have a calibration issue. You just need to know how to meter to have the result you want.

First you should be proficient in nailing flash exposures with film, if this is not the case then first master that, you can simply test with a dslr, this is calculating flash power manually and then checking the practical result to see if it is like you predicted.

From that you may rate the paper medium at several EI, say from ISO 1 to ISO 8, and see what Exposure index is good for you.

I the image #2 you could do something better, this is extracting the dark slide from the film holder only 1/2", the you fire the flash once, then you extract the dark slide 1/2" more, firing again... total 10 times. I that way with that single sheet of paper you would have 10 exposures like if it was test strip with the enlarger.

You also may try with different paper grades, with graded paper or with multigrade paper and placing filters on the lens or on the flash.

tonyowen
18-Feb-2019, 09:36
you can simply test with a dslr, this is calculating flash power manually and then checking the practical result to see if it is like you predicted.

From that you may rate the paper medium at several EI, say from ISO 1 to ISO 8, and see what Exposure index is good for you.

I the image #2 you could do something better, this is extracting the dark slide from the film holder only 1/2", the you fire the flash once, then you extract the dark slide 1/2" more, firing again... total 10 times. I that way with that single sheet of paper you would have 10 exposures like if it was test strip with the enlarger.

[You also may try with different paper grades, with graded paper or with multigrade paper and placing filters on the lens or on the flash.

Pere, Answers follow to your paragraphs

Unfortunately my Coolpix does not allow manual selection of flash and I do not want to risk using my 'old' flashguns on the digital camera in case of overloading the DSLR's circuitry/U]

Agreed that is something I should do

U]I understand what you are saying, but do not understand the logic. #2 was taken at full power of the Cobra flash, so multiple exposures will show the result of increased flash power - that I do not have with the Cobra. Unless you mean the 'correct' result would indicate the GN/flash power necessary to give that result albeit with a more powerful flash gun or by studio lighting.

usually I have a yellow filter on the camera lens

I've found the reason for the discrepancy in the meter readings. The Weston was angled downwards whereas the Coolpix was horizontal. Comparing both in similar attitudes gives almost identical results.

regards
Tony

Pere Casals
18-Feb-2019, 10:53
I do not want to risk using my 'old' flashguns on the digital camera in case of overloading the DSLR's circuitry

Use a remore trigger, this is \$16, you get rid of cables and you don't risk the DSLR

187886

GN/flash power necessary to give that result albeit with a more powerful flash gun or by studio lighting.[/U]

What you need to find is the ISO rating of paper that delivers a correct exposure by using the GN of your flash and the flash to subject distance.

You always can place the flash closer to subject if flash power is not enough, or (for still subjects) you can always fire a series of flashes.

The relevant parameter you have to find is the practical ISO of the paper, from that you always may check the right result in the dslr and then calculating the equivalent power for the view camera/paper.

In the past Polaroid instant film was used to check what was to be obtained with the view camera for important shots, today we have DSLRs, at least this would be useful to learn if you are in the good path.

usually I have a yellow filter on the camera lens

In that case you have to know that with yellow (vs no filter) will need a different exposure, if paper is multi-grade then with yellow filter you also will have a lower contrast.

DrTang
18-Feb-2019, 17:44
I would start by putting the flash - on full - right next to the subject and blasting it about 3 or 4 or 5x the suggested GN aperture...just to see if you get ANYTHING

if not..then it is a mechanical problem and not a light one

if you get something..and it is over exposed..just keep walking it back until you get what you want

tonyowen
20-Feb-2019, 12:26
Use a remore trigger, this is \$16, you get rid of cables and you don't risk the DSLR
In the past Polaroid instant film was used to check what was to be obtained with the view camera for important shots, today we have DSLRs, at least this would be useful to learn if you are in the good path. In that case you have to know that with yellow (vs no filter) will need a different exposure, if paper is multi-grade then with yellow filter you also will have a lower contrast.

Pere,
My Cobra flash gun has a low trigger voltage so It can be used on my Nikon Camera.
Attached are two images with the relevant EXIF data. I set the ISO to 50 therefore the GN of the flash was 32.5
The 'image subject' was about 5m away hence f6.3
So, my flash GN appear to be okay and the resulting image from the DSLR seems okay so why the problem with paper???.
The info I have is that the apparent GN for ISO 6 paper is less than 4 which does not make sense at all.

My comment about the yellow filter was for info. No filter was used on any of the previous images. I know that the filter in question need a 1 stop correction.

regards
Tony
exif data below
187926 187927
Filename - DSCN0201.JPG
ImageDescription -
Make - NIKON
Model - E8800
ExposureTime - 1/60.1 seconds
FNumber - 6.00
ExposureProgram - Aperture priority
ISOSpeedRatings - 50
LightSource - Auto
Flash - Flash fired, Compulsory flash mode
FocalLength - 11.80 mm
ISO Setting - 50
Color Mode - COLOR
Flash Setting - NORMAL
Unknown - 9.04
ISO Selection – MANUAL

Filename - DSCN0202.JPG
ImageDescription -
Make - NIKON
Model - E8800
ExposureTime - 1/60.1 seconds
FNumber - 6.00
ExposureProgram - Aperture priority
ISOSpeedRatings - 50
LightSource - Auto
Flash - Flash fired, Compulsory flash mode
FocalLength - 11.80 mm
ISO Setting - 50
Color Mode - COLOR
Flash Setting - NORMAL
Unknown - 9.04
ISO Selection - MANUAL

Pere Casals
20-Feb-2019, 12:39
The info I have is that the apparent GN for ISO 6 paper is less than 4 which does not make sense at all.

Anyway you may always shot the flash a number of times, to multiply the effective power, for testing and to know what flash you need.

My comment about the yellow filter was for info. No filter was used on any of the previous images. I know that the filter in question need a 1 stop correction.

Well, in this case the factor may be greater: 1 stop is for panchromatic film, but paper is orthochromatic... Filter factors are orientative...

Dan Fromm
20-Feb-2019, 13:21
The info I have is that the apparent GN for ISO 6 paper is less than 4 which does not make sense at all.

Why doesn't it make sense?

tonyowen
20-Feb-2019, 13:48
Why doesn't it make sense?

Because there is no logic I can understand that makes sense. Somehow the 'power' of the flash is lost between the flash gun itself and the paper within the camera.

Yes the duration of the flash is short [1/1000th second], but the intensity is large. Maybe it is the structure and/or surface of the paper that absorbs most of that energy and any residue 'exposes' an image on the paper!!!!!!!

I could accept such a proposition, but no one is stating it!!

All I know is the flashgun's output is 'correct' for film and digital capture - but not for (multigrade) paper negatives.

regards
Tony

Dan Fromm
20-Feb-2019, 14:55
Lessee now, GN, ISO 100 meters, is 30. Or 46.

One stop down from ISO 100 is ISO 50. One stop down from ISO 50 is ISO 25. One stop down from ISO 25 is ISO 12.5. One stop down from ISO 12.5 is ISO 6.25. One stop down from ISO 6.25 is ISO 3.125. Close enough. 50, 25, 12.5, 6.25, 3.125. 1, 2, 3, 4, 5 stops down from ISO 100.

One stop down from GN 46 is 32. One stop down from GN 32 is 22. One stop down from 22 is 16. One stop down from 16 is 11. One stop down from 11 is 8. One stop down from 8 is 5.6. 1, 2, 3, 4, 5. 22, 16, 11, 8, 5.6.

Knock off a stop because flash manufacturers exaggerate around 1 stop and you're at GN 4.

When trying to solve this kind of problem, counting on fingers will do.

Jac@stafford.net
20-Feb-2019, 15:28
When trying to solve this kind of problem, counting on fingers will do.

Darn, I have only six fingers. And I wear shoes. :)

OP - your flash does not produce a lot of light in total. Yes, lots of light for its duration which is so very short. And another reminder that multiple pops of an electronic flash does not produce the sum of pops. Reciprocity is a pain.

Dan Fromm
20-Feb-2019, 15:38
JAC, six fingers are enough for the OP.

1 pop, 2 pops, 4 pops, 8 pops, 16 pops, 32 pops, ... + 0 stops, + 1 stop, + 2, + 3, + 4, + 5, ...

It ain't reciprocity.

Jac@stafford.net
20-Feb-2019, 15:56
JAC, six fingers are enough for the OP.

1 pop, 2 pops, 4 pops, 8 pops, 16 pops, 32 pops, ... + 0 stops, + 1 stop, + 2, + 3, + 4, + 5, ...

It ain't reciprocity.

We have a gentleman's bet on the reciprocity issue unless there is another name for the same outcome.
--
Jac with the six-bit calculator

Dan Fromm
20-Feb-2019, 16:05
Reciprocity problems at 1/1000? Are you serious?

That's a long duration for an electronic flash, even a potato masher at full power. That said, IIRC my Agfa 643's full power flash duration is 1/200. That one's not for hummingbirds.

Bob Salomon
20-Feb-2019, 17:04
Lessee now, GN, ISO 100 meters, is 30. Or 46.

One stop down from ISO 100 is ISO 50. One stop down from ISO 50 is ISO 25. One stop down from ISO 25 is ISO 12.5. One stop down from ISO 12.5 is ISO 6.25. One stop down from ISO 6.25 is ISO 3.125. Close enough. 50, 25, 12.5, 6.25, 3.125. 1, 2, 3, 4, 5 stops down from ISO 100.

One stop down from GN 46 is 32. One stop down from GN 32 is 22. One stop down from 22 is 16. One stop down from 16 is 11. One stop down from 11 is 8. One stop down from 8 is 5.6. 1, 2, 3, 4, 5. 22, 16, 11, 8, 5.6.

Knock off a stop because flash manufacturers exaggerate around 1 stop and you're at GN 4.

When trying to solve this kind of problem, counting on fingers will do.

100m? Or did you mean 10m or 3m or?

Dan Fromm
20-Feb-2019, 18:04
Bob, guide numbers are rated for distances in feet and for distances in meters. I didn't write "100m." The op stated early on that his flash is rated 30 and 46, for ISO 100 meters. That's not flash-to-subject distance, that's how the flash's GN is to be interpreted.

Bob Salomon
20-Feb-2019, 18:28
Bob, guide numbers are rated for distances in feet and for distances in meters. I didn't write "100m." The op stated early on that his flash is rated 30 and 46, for ISO 100 meters. That's not flash-to-subject distance, that's how the flash's GN is to be interpreted.

Deceptive at first reading.

tonyowen
21-Feb-2019, 02:10
Response to posts 73 thru 80

For clarity, the Cobra D650 has a GN of 46 at 100 ISO [meters] when set at the 85mm zoom. This is what I'm using.
Therefore, the GN at 6 ISO is 11.75 one stop down gives me a GN of 8.30 [???]. But why should the GN be one stop down at 6 ISO but not at 100 ISO or 50 ISO??

Whereas my estimated effective GN of about 4 for multigrade paper negative based on results [Post #70] infers an ISO of less than 1 for the paper

Quote from the Cobra manual "Flash duration Manual 1/1000th sec at full power" - again this is what I'm using.

I'm assuming that the flash output is daylight not tungsten. Therefore, given that multigrade paper is [often/mainly] exposed with tungsten light and given that film is panchromatic film, but paper is orthochromatic [Pere] might this explain the paradox I have between the results of the three media types????

Do we continue this "multi-logue"??????

regards all round

Tony

Dan Fromm
21-Feb-2019, 05:56
But why should the GN be one stop down at 6 ISO but not at 100 ISO or 50 ISO??

Because flash manufacturers are, to be polite, optimists. To be impolite, liars.

tonyowen
21-Feb-2019, 06:26
Because flash manufacturers are, to be polite, optimists. To be impolite, liars.

sorry Dan I phrased my comment on #81 wrongly.

The film images at 100 ISO and the digital images at 50 ISO taken using the Cobra flash seem okay.
Hence if the flash GN is [seemingly] correct for ISOs 100 & 50 then why not at other ISOs.
Surely any optimism will be linear.

I agree with your comment regarding (all and any) manufacturers and their sales/publicity department.

regards
Tony

Dan Fromm
21-Feb-2019, 06:41
Tony, I've had flash meters for years. The only flashes I've tested with meters -- testing with negative film has many frailties, testing with reversal is better but not perfect -- that matched their makers' claims were Minoltas. All of the others ran around one stop under.

tonyowen
21-Feb-2019, 09:21
Tony, I've had flash meters for years. The only flashes I've tested with meters -- testing with negative film has many frailties, testing with reversal is better but not perfect -- that matched their makers' claims were Minoltas. All of the others ran around one stop under.

Dan how does your comment "Because flash manufacturers are, to be polite, optimists. To be impolite, liars. " relate to flash meter manufacturers in terms of the [claimed] accuracy, precision and repeatability of their products??????

regards
Tony

Dan Fromm
21-Feb-2019, 09:42
Their claimed GNs are usually one stop more powerful than measured. Repeatable, yes if allowed to recharge between full power pops. Accurate, no.

hsandler
21-Feb-2019, 20:38
I’ve found a reference that states: As a rough rule of thumb, multiplying the square root of the (wattsecond) Ws number by 4 gives a indicator of the metric GN at ISO 100.

Therefore assuming your shutter is set at 1/60th second and your studio lights give 1500w power

We get 1500 x 0.017 = 25Ws

Therefore GN = SQRT(Ws) x 4 = 20

Both of my flash guns have a higher GN at 100 ISO

However, as stated above this is a rough rule of thumb.
regards
Tony

Tony, I think Phil probably meant he used three 500Ws flash heads, not 500W, as he was writing about flash, not continuous lights. So take the 1/60s shutter speed out of the calculation. That gives a much higher GN for his setup, using your rule of thumb, than your two flashes. Couple that with the effective ISO of the paper being much less than 6 when using flash due to its orthochromatic response and possibly reciprocity (paper not intended for brief intense flash) and I think your results are explainable. Your equipment seems to function; you just need a lot of light.

Bob Salomon
22-Feb-2019, 06:47
Tony, I think Phil probably meant he used three 500Ws flash heads, not 500W, as he was writing about flash, not continuous lights. So take the 1/60s shutter speed out of the calculation. That gives a much higher GN for his setup, using your rule of thumb, than your two flashes. Couple that with the effective ISO of the paper being much less than 6 when using flash due to its orthochromatic response and possibly reciprocity (paper not intended for brief intense flash) and I think your results are explainable. Your equipment seems to function; you just need a lot of light.

It is a meaningless formula since WS is not a power rating, it’s an input rating and the output will vary with each makers pack rated at 1500 WS plus the formula does not provide for the angle of coverage.

WS is pretty much like horsepower. Horsepower will not tell you your miles per gallon or time to 60mph or time and speed in the ¼ mile.

All you can assume from hp is it probably uses more fuel per mile, it probably can do a fast 0 to 60 and perform well in the quarter mile. But it can not and will not let you assume how well or how much fuel. Watt seconds is the same, it is nice for advertising but it can not convert, by itself, to a useable GN or aperture!

Pere Casals
22-Feb-2019, 07:03
It is a meaningless formula since WS is not a power rating, it’s an input rating and the output will vary with each makers pack rated at 1500 WS plus the formula does not provide for the angle of coverage.

I agree, the angle of coverage is basicly variable because we always use a kind of light modifier, the shape or the reflector itself modifies that angle...

WS rating is not to adjust aperture, but to compare capability of different strobes.

To me the WS is the most important parameter of an strobe, because it tells what we can do with it, but of course WS does not tell the aperture depending on power selector position, this is told by the flash meter...

Tin Can
22-Feb-2019, 07:10
Full disclosure: I paid full retail for my collection of PCB studio lighting. I like it, some don't.

The founder, now deceased, explains a lot about flash on this page.

https://paulcbuff.com/Studio-Flash-Explained.html

And i often use 10 fingers to count stops up and down, after I run out I use paper and pencil. Pencil as I make mistakes...

Bob Salomon
22-Feb-2019, 07:10
I agree, the angle of coverage is basicly variable because we allways use a kind of light modifier, the shape or the reflector itself modifies that angle...

WS rating is not to adjust aperture, but to compare capability of different strobes.

To me the WS is the most important parameter of an strobe, because it tells what we can do with it, but of course WS does not tell the aperture depending on power selector position, this is told by the flash meter...

WS tells you nothing other then one strobe has more storage capacity then another one.
BCPS or ECPS tells you what the output is at the desired degree of coverage.

If you base anything on WS then you are simply ass u me ing!

Pere Casals
22-Feb-2019, 07:46
WS tells you nothing other then one strobe has more storage capacity then another one.
BCPS or ECPS tells you what the output is at the desired degree of coverage.

To me BCPS or ECPS is only relevant if we don't use a modifier. If I use the strobe in a Softbox, for example, then what I want to know is the WS to compare the strobes.

Let me say an example, a higher BCPS strobe may have lower WS, if I want to use the strobe outdoors in a softbox then I'll want the higher WS, being the BCPS irrelevant.

What I understand is that WS is an electric rating, energy Joules in the storage. This is 1/2 Farads x V2. Farads is the capacity of the capacitors, V is the working voltage used to load the capacitors.

Thus WS tells the energy we have, depending on our reflector/modifier we may concentrate more or less the light, but if we are able to modify the angle then what counts is the energy we have.

Tin Can
22-Feb-2019, 08:04
Lifted in full from PCB webpage, https://paulcbuff.com/Efficiency-Wattseconds-and-Units-of-Measure

"For reference, conventional 120 VAC household bulbs emit approximately 17 lumens of light per watt of electrical energy. Thus, the efficacy (efficiency) is 17 Lumens per watt. A typical 100 Watt household bulb emits approximately 1700 Lumens. If a 1700 Lumen bulb is operated for one second (i.e. a one second exposure time), the amount of light emitted is 1700 Lumenseconds. Lumen information is generally printed on the bulb itself.

Originally, all studio flash systems were central power pack or box and cable systems. Here, the power supply was (is) properly rated in terms of how many Wattseconds (Ws) of electrical energy were available to deliver to the flash heads attached to it. Depending upon how many heads were attached, the length of cables, type of flashtubes and other factors, such a system might deliver anywhere from about 15 to 45 Lumenseconds per Ws. Thus, it is impractical to specify such systems in Lumenseconds (actual light output) because light output is variable and dependent on many factors. Accordingly, the industry long ago adopted the Ws rating for power packs – a rating that does not actually indicate the light output.

With the advent of modern monoflash units, a single flashtube is connected to the internal power supply and, if properly designed, optimized to provide high and stable efficiency in the conversion of WS to Lumenseconds. As with LEDs, fluorescent and other light sources that produce sunlight balanced light, the maximum achievable efficacy is on the order of 50 Lumens per watt (or 50 Lumenseconds per Ws).

In attempting to draw comparisons between high efficiency monoflash units and older box and cable systems, the informal term Effective Wattseconds was coined. The logic was that if a certain monoflash unit produced the same amount of light as a typical 400 Ws box and cable system, the monoflash could be called “400 Effective Ws” regardless of the actual number of Ws contained in the monoflash.

Exactly the same relationship exists in the marketing of high efficiency household bulbs and lamps. It is typical, for instance, for a 13W compact fluorescent bulb to be labeled “50W*”, indicating it produces the same number of Lumens as a typical 50W tungsten bulb.

However, in both cases, the use of such arbitrary terms are subject to abuses and are based upon what the manufacturer decides to use as a reference for “typical” systems. The only proper and logical answer is for manufacturers to properly define lighting systems, using the actual Lumen and Lumensecond terms.

In recent years, most manufacturers of studio flash have improved their designs such that the efficacy of most quality flash systems is in the range of 35 to 45 Lumenseconds per Ws, regardless of configuration. Accordingly, users may more comfortably compare systems using the incorrect Ws term the manufacturers so stubbornly hang onto. But there do indeed remain some flash systems, both monolights and box and cable systems, whose efficacy is much lower than this and which cannot be properly compared using the Ws term."

Pere Casals
22-Feb-2019, 08:46
the Ws term

Randy, IMHO today WS is only related to electrical energy storage capability of the capacitors. See here photography section: https://en.wikipedia.org/wiki/Joule#Watt_second

Watt-Second ratings are purely based on the capacitor and on the top voltage.

Today most quality flash tubes have similar efficiency, but of course a good manufacturer may generate a bit more light and less heat.

Of course there is an equivalence to other units, but the WS is Joules stored in the capacitor, IMHO.

Tin Can
22-Feb-2019, 08:51
Not arguing simply trying to clarify

Output is what we use

Pere Casals
22-Feb-2019, 09:42
Output is what we use

Yes, of course...

But IMHO the output amount is the easy thing, at the end we release stored energy in a xenon lamp, and this process is pretty similar in different devices.

The difficult thing comes when we spread the photons on the scene...

What's clear is that SLRs long ago were able not fail a single exposure, Nikon in special. Long ago they invented "D" type lenses that were telling the camera at what distance we had focus, so camera could perfectly adjust power.

In DSLRs today we have i-TTL and e-TTL, and Ratio... Strobes work perfect, we only say what amount of fill vs key and the camera makes perfect exposures.

In LF we only need to do the same manually...

Bob Salomon
22-Feb-2019, 10:33
To me BCPS or ECPS is only relevant if we don't use a modifier. If I use the strobe in a Softbox, for example, then what I want to know is the WS to compare the strobes.

Let me say an example, a higher BCPS strobe may have lower WS, if I want to use the strobe outdoors in a softbox then I'll want the higher WS, being the BCPS irrelevant.

What I understand is that WS is an electric rating, energy Joules in the storage. This is 1/2 Farads x V2. Farads is the capacity of the capacitors, V is the working voltage used to load the capacitors.

Thus WS tells the energy we have, depending on our reflector/modifier we may concentrate more or less the light, but if we are able to modify the angle then what counts is the energy we have.

BCPS or ECPS is determined by the output of the flash and the angle of coverage of the reflector, or lack of one with bare bulb.

WS do not enter into output at any time!

Bob Salomon
22-Feb-2019, 10:38
Lifted in full from PCB webpage, https://paulcbuff.com/Efficiency-Wattseconds-and-Units-of-Measure

"For reference, conventional 120 VAC household bulbs emit approximately 17 lumens of light per watt of electrical energy. Thus, the efficacy (efficiency) is 17 Lumens per watt. A typical 100 Watt household bulb emits approximately 1700 Lumens. If a 1700 Lumen bulb is operated for one second (i.e. a one second exposure time), the amount of light emitted is 1700 Lumenseconds. Lumen information is generally printed on the bulb itself.

Originally, all studio flash systems were central power pack or box and cable systems. Here, the power supply was (is) properly rated in terms of how many Wattseconds (Ws) of electrical energy were available to deliver to the flash heads attached to it. Depending upon how many heads were attached, the length of cables, type of flashtubes and other factors, such a system might deliver anywhere from about 15 to 45 Lumenseconds per Ws. Thus, it is impractical to specify such systems in Lumenseconds (actual light output) because light output is variable and dependent on many factors. Accordingly, the industry long ago adopted the Ws rating for power packs – a rating that does not actually indicate the light output.

With the advent of modern monoflash units, a single flashtube is connected to the internal power supply and, if properly designed, optimized to provide high and stable efficiency in the conversion of WS to Lumenseconds. As with LEDs, fluorescent and other light sources that produce sunlight balanced light, the maximum achievable efficacy is on the order of 50 Lumens per watt (or 50 Lumenseconds per Ws).

In attempting to draw comparisons between high efficiency monoflash units and older box and cable systems, the informal term Effective Wattseconds was coined. The logic was that if a certain monoflash unit produced the same amount of light as a typical 400 Ws box and cable system, the monoflash could be called “400 Effective Ws” regardless of the actual number of Ws contained in the monoflash.

Exactly the same relationship exists in the marketing of high efficiency household bulbs and lamps. It is typical, for instance, for a 13W compact fluorescent bulb to be labeled “50W*”, indicating it produces the same number of Lumens as a typical 50W tungsten bulb.

However, in both cases, the use of such arbitrary terms are subject to abuses and are based upon what the manufacturer decides to use as a reference for “typical” systems. The only proper and logical answer is for manufacturers to properly define lighting systems, using the actual Lumen and Lumensecond terms.

In recent years, most manufacturers of studio flash have improved their designs such that the efficacy of most quality flash systems is in the range of 35 to 45 Lumenseconds per Ws, regardless of configuration. Accordingly, users may more comfortably compare systems using the incorrect Ws term the manufacturers so stubbornly hang onto. But there do indeed remain some flash systems, both monolights and box and cable systems, whose efficacy is much lower than this and which cannot be properly compared using the Ws term."

This is an admirable attempt by a company whose founder merchandised inexpensive flash with impressive, but meaningless power ratings.

BCPS AND ECPS are the actual outputs of a flash and, other then GN or f stop the only valid expressions of flash output.

Having been involved with Broncolor flash, Rollei Studio Flash, Multiblitz Flash, as well as some other units both as a user and a marketeer Lumens or any expression involving lumens or WS is gibberish.

Bob Salomon
22-Feb-2019, 10:47
Yes, of course...

But IMHO the output amount is the easy thing, at the end we release stored energy in a xenon lamp, and this process is pretty similar in different devices.

The difficult thing comes when we spread the photons on the scene...

What's clear is that SLRs long ago were able not fail a single exposure, Nikon in special. Long ago they invented "D" type lenses that were telling the camera at what distance we had focus, so camera could perfectly adjust power.

In DSLRs today we have i-TTL and e-TTL, and Ratio... Strobes work perfect, we only say what amount of fill vs key and the camera makes perfect exposures.

In LF we only need to do the same manually...

Nonsense! Output as expressed by a GN, an Fstop, BCPS or ECPS over a given degree of coverage is the only accurate way to determine exposure with a flash.

The only exception to this were/are studio strobes with a quartz halogen modeling light centered in the flash tube and both covered with a frosted glass dome with a power pack with fully proportional modeling light control and constant flash duration at all power levels.
With this type of flash a standard light meter can give the proper flash exposure. Examples of this type of control were the Rollei and Berger studio flash systems, some Broncolor and Multiblitz as well as some other European studio flash systems.

Quartz halogen modeling lamp because the by products of their burning are redepoisited on the filament rather then on the glass globe so, unlike incandescent bulbs, their output does not diminish with use.

Tin Can
22-Feb-2019, 11:59
Paul C Buff Einsteins which I use have the same EU type characteristics, "using a quartz halogen modeling light centered in the flash tube and both covered with a frosted glass dome withOUT a power pack however with fully proportional modeling light control and constant flash duration at all power levels."

I have checked mine with D750, Sekonic DR758 and Cyber Commander plus LF film.

Nonsense! Output as expressed by a GN, an Fstop, BCPS or ECPS over a given degree of coverage is the only accurate way to determine exposure with a flash.

The only exception to this were/are studio strobes with a quartz halogen modeling light centered in the flash tube and both covered with a frosted glass dome with a power pack with fully proportional modeling light control and constant flash duration at all power levels.
With this type of flash a standard light meter can give the proper flash exposure. Examples of this type of control were the Rollei and Berger studio flash systems, some Broncolor and Multiblitz as well as some other European studio flash systems.

Quartz halogen modeling lamp because the by products of their burning are redepoisited on the filament rather then on the glass globe so, unlike incandescent bulbs, their output does not diminish with use.

Pere Casals
22-Feb-2019, 12:46
Output as expressed by a GN, an Fstop, BCPS or ECPS over a given degree of coverage is the only accurate way to determine exposure with a flash.

The only exception to this were/are studio strobes with a quartz halogen modeling light centered in the flash tube and both covered with a frosted glass dome with a power pack with fully proportional modeling light control and constant flash duration at all power levels.
With this type of flash a standard light meter can give the proper flash exposure.

Of course I agree that aperture will be determined by GN and strobe to subject distance...

But strobe capability is told by WS.

Imagine you illuminate a group portrait, say 4m x 3m. If flash angle is narrower you will have to place it farther... So if placing the flashes at the distance that will cover all the group then what rules performance is WS.

Same with a softbox, GN is irrelevant, what counts is WS in that case.

Bob Salomon
22-Feb-2019, 13:59
Of course I agree that aperture will be determined by GN and strobe to subject distance...

But strobe capability is told by WS.

Imagine you illuminate a group portrait, say 4m x 3m. If flash angle is narrower you will have to place it farther... So if placing the flashes at the distance that will cover all the group then what rules performance is WS.

Same with a softbox, GN is irrelevant, what counts is WS in that case.

Get your head into the facts. WS are only a measure of energy storage, it is also referred to as joules. They have no relationship with the output of a flash and the most effective flash can only output 80% of its stored capacity.

Learn to use the correct terms, BCPS, ECPS, GN or f stop and get input capacities out of your head.

tonyowen
23-Feb-2019, 05:00
[QUOTE=hsandler;1485360 ..... the effective ISO of the paper being much less than 6 when using flash due to its orthochromatic response and possibly reciprocity (paper not intended for brief intense flash) and I think your results are explainable. Your equipment seems to function; you just need a lot of light.[/QUOTE]

Please can we get away from the rants and discuss my original query.

Okay, does anyone challenge the above quote from Hsandler?

It seems to match my observations and tests, but I do not understand the why and wherefore
My post #59 and result #2 infer that the effective flash GN was/is between 3 and 4 [ f4.7 @ 0.7m]
In turn, given my flash has a GN of 46 at ISO100 then the apparent paper ISO is less than 1.56 [www.scantips - understanding flash guide numbers]

regards
Tony

Pere Casals
23-Feb-2019, 05:42
paper ISO

Tony, just calculate it...

First this is not an ISO Speed, but a suitable EI, (Exposure Index).

I insist. Take a DSLR at ISO 100 and see the right flash power/aperture. Then make a bracketing with paper until you find the right flash/aperture. Comparing the DSLR vs paper then you have your suitable EI for paper.

Tin Can
23-Feb-2019, 06:49
I may have time today.

Tell us exactly what paper you are using.

You only stated Ilford MG.

FB or RC, matt or glossy, guess the age as none is dated.

Any other variables you know of.

Thank you

tonyowen
23-Feb-2019, 08:19
I may have time today.Tell us exactly what paper you are using. You only stated Ilford MG. FB or RC, matt or glossy, guess the age as none is dated. Any other variables you know of. Thank you

Randy, the following is off the box - both sides

Ilford MGIV RC de luxe; 8x10 sheets 100 box; medium weight, Pearl;
MG4RC44M; 09C501C91; 1455 2089; Harman Technology Ltd

Age unknown - best guess circa 10 years????????

regards

Tony

hsandler
24-Feb-2019, 13:08
Please can we get away from the rants and discuss my original query.

Okay, does anyone challenge the above quote from Hsandler?

It seems to match my observations and tests, but I do not understand the why and wherefore
My post #59 and result #2 infer that the effective flash GN was/is between 3 and 4 [ f4.7 @ 0.7m]
In turn, given my flash has a GN of 46 at ISO100 then the apparent paper ISO is less than 1.56 [www.scantips - understanding flash guide numbers]

regards
Tony

Tony there's yet another factor that I think may have been lost in the discussion. In your post #69 the photo of the table and chairs established the GN of your flash is indeed fairly consistent with its rating of 46 in metres at ISO 100. In your post #59, a paper negative photo outdoors established the paper exposed at EI 6 is indeed fairly consistent with ISO 6 for continuous daylight exposure with your development process (negative looks a little thin to me though in the photo, but these things are hard to tell--it's in the ballpark anyway). But way way back near the beginning of the thread, you used GN and paper EI and distance to establish what you predicted should be the right aperture for your still life photo; however, you just summed the distance from the flash to the bounce surface and from the bounce surface to the subject. That's going to be way off, especially for a bounce surface that is not a large mirrored surface. The rule of thumb for bounce flash is you lose 1-2 stops in bouncing off a white ceiling, and that's in addition to the extra distance of the light path. The reason is that a lot of the light is absorbed or scattered off in other directions by the bounce surface. You can verify this by doing a bounce flash photo of something with your digital camera (set it on B in the dark and manually flash your Cobra flash off the ceiling with measured distances and see).

So you have three factors that could account for your underexposure: calculation ignored bounce loss, ortho paper may be less sensitive to bluish flash than daylight or tungsten, and paper may have reciprocity loss for brief flashes (1/1000s at f16 may give less density on the negative than 1/60s at f4).

The thread has gotten very long, and perhaps I missed if you verified these last two things by doing a paper exposure with direct flash but not bounced. The tests with flashing right into the lens only showed that your shutter is working fine on X synch.

Tin Can
24-Feb-2019, 13:23
I have not got to my test yet.

Agree a bounce off the ceiling vastly changes flash effect

Luis-F-S
24-Feb-2019, 13:28
I use a flash meter. Using guide numbers in general and for large format is a fallacy.

Dan Fromm
24-Feb-2019, 14:16
I use a flash meter. Using guide numbers in general and for large format is a fallacy.

Has always worked well for me for closeup work. But my GNs, not the manufacturer's.

Tin Can
24-Feb-2019, 19:23
I tested D750 ISO 100 and 30 year old (a guess) Ilford RC MG IV Pearl I rated at 4 ISO.

2 setup pics on this page.

#1 from above behind with the Strobe Model lamp at full power, no other lighting on at anytime for all tests. iPhone

#2 seconds later of the 4X5 GG.

All shots on next page are shot at f22 on both the D750 and 4X5 from same tripod without moving it. Check D750 exif. The Paul C Buff Einstein strobe was set art 1/32 power for both flash and model lamp for the D750 at 100 ISO f22 aperture. Exposure time was 30 seconds under model lamp and 1/30th with the strobe which was obviously way faster, maybe 1/5000th a second.

Only 2 paper negatives were exposed. I have never shot paper negs in studio and only 2 paper pinhole in the Sun 20 years ago.

The paper was exposed at full power at close distance exactly the same as D750 both by strobe and model lamp. 32 times more light as used for the D750. Again timed at 30 second f22 with full power model lamp and 1/30th for full power strobe.

I spent more time thinking about this than doing it. I did check incident light with Sekonic DR758. I calculated 1/2 stop bellows factor but did not compensate.

The D750 shots are unmanipulated jpeg, no exposure adjustments outside camera.

The paper negs are also unmanipulated, but flipped horizontally and inverted to match the D750 positives.

https://farm8.staticflickr.com/7822/33327687768_dd307e4f45_b.jpg (https://flic.kr/p/SM47sm)IMG-2105 (https://flic.kr/p/SM47sm) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

https://farm8.staticflickr.com/7879/40238334373_ea96d186ab_b.jpg (https://flic.kr/p/24iHYVK)IMG-2106 (https://flic.kr/p/24iHYVK) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

Page 2 with results in a few minutes.

Tin Can
24-Feb-2019, 19:46
The results are a bit confusing as images show reversed brightness between DSLR and paper with lighting type.

My opinion is paper negs need a lot of light and IF strobe reciprocity on paper negs does exist it is not extreme.

Obviously we can capture both ways and we can do it better.

2 or more experiments could be done to reinforce results and improve exposures.

Feel free to do a better job and post results.

https://farm8.staticflickr.com/7920/40238583683_b8b0a942b4_b.jpg (https://flic.kr/p/24iKg3c)1 D750 1-30sec 1-32power strobe (https://flic.kr/p/24iKg3c) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

https://farm8.staticflickr.com/7901/32261186707_a0113ac8c0_b.jpg (https://flic.kr/p/R9P1R2)2 D750 30 secs 1-32 power 250 watt quartz (https://flic.kr/p/R9P1R2) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

https://farm8.staticflickr.com/7834/32261186787_9f8caf8e03_b.jpg (https://flic.kr/p/R9P1Sp)3 paper ISO 4 Full Power Strobe f22 (https://flic.kr/p/R9P1Sp) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

https://farm8.staticflickr.com/7860/32261180917_95f0fecf7f_b.jpg (https://flic.kr/p/R9NZ8c)4 paper ISO 4 250 watt Quartz 100% f22 (https://flic.kr/p/R9NZ8c) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

tonyowen
25-Feb-2019, 04:15
Tony there's yet another factor that I think may have been lost in the discussion. But way way back near the beginning of the thread, you used GN and paper EI and distance to establish what you predicted should be the right aperture for your still life photo; however, you just summed the distance from the flash to the bounce surface and from the bounce surface to the subject.

I think it is post #1 you are referring to. In that post I was asking about a general question/situation and the distance referred was direct OR bounce. I agree that if bounce was used that some correction factor should be used due to the reflecting surface.

None of the tests I have done have involved bounced light.

regards

Tony

tonyowen
25-Feb-2019, 04:43
[QUOTE=Randy Moe;1485876]My opinion is paper negs need a lot of light and IF strobe reciprocity on paper negs does exist it is not extreme./QUOTE]

Randy, thank you for the tests you have done. I assume your strobe is model E640 which has an output of 2.5 to 640ws.
I think for some tests you used only the modelling light for which I cannot find the light output/power/ws/gn-equiv or whatever.

Your testing [I think] confirmed that my setup - without pops - does not allow sufficient illumination of the subject for it to register on the paper negative at realistic (for me) camera to subject distances.

regards

Tony

Bob Salomon
25-Feb-2019, 06:34
[QUOTE=Randy Moe;1485876]My opinion is paper negs need a lot of light and IF strobe reciprocity on paper negs does exist it is not extreme./QUOTE]

Randy, thank you for the tests you have done. I assume your strobe is model E640 which has an output of 2.5 to 640ws.
I think for some tests you used only the modelling light for which I cannot find the light output/power/ws/gn-equiv or whatever.

Your testing [I think] confirmed that my setup - without pops - does not allow sufficient illumination of the subject for it to register on the paper negative at realistic (for me) camera to subject distances.

regards

Tony

Whose INPUT is 2.5 to 640 WS!!!

Tin Can
25-Feb-2019, 06:56
[QUOTE=tonyowen;1485898]

Whose INPUT is 2.5 to 640 WS!!!

Bob that is the advertised adjustable output range. https://www.paulcbuff.com/Flash-Units/einstein-flash-unit.html

I just tried measuring 100% model lamp lumens at 1 ft directly in front of the standard reflector with an app https://www.paulcbuff.com/Light-Modifiers/Reflectors/7-Standard-Reflector.html

They never quantify the model lamp actual output, they do state it is proportional to the flash.

My app on iPhone SE gave varying results as did low angle full morning Sun.

Maybe 5000 lumens at 1 ft model lamp.

The Sun 4000 lumens.

I will be getting a Lux meter soon.

Bob Salomon
25-Feb-2019, 07:22
[QUOTE=tonyowen;1485898]

Whose INPUT is 2.5 to 640 WS!!!

The flash Randy used. WS, or Joules, is only input. It can not be output.

Output is F stop, GN, ECPS or BCPS. It is never WS!!!

Tin Can
25-Feb-2019, 07:39
OK Bob, I used more incorrect terminology. :(

All I can do is read it and try to use in real life. IRL

I did use f stop readings on my Sekonic at the subject distance. I got f22 with both full power strobe and model lamp DEPENDANT upon ISO setting. I shot with recommended TIME with model lamp and used 1/30 sync for both shutters.

Einstein™ Flash Unit
Watt seconds 640 Ws
Power Variability 9 f-stops (full to 1/256 power)
Recycle to Full 1.7 sec.
Flash Duration (t.5) 1/2000 sec. (at full power)
Flash Duration (t.1) - in Action Mode 1/588 sec. (at full power) | 1/13,500 sec. (at 1/256 power)
Flash Duration (t.1) - in Color Mode 1/588 sec. (at full power) | 1/8,000 sec. (at 1/256 power)
Power Requirements Automatic power switching from 95 to 265 VAC, 50/60 Hz (no lamp change or user attention required)
Average Current Draw Brief initial recycle surge current of 8.5A; average draw of 8A
Sync / Trigger Voltage Less than 5 volts (safe for use with DSLR cameras)
Modeling Lamp 250 W, 120VAC bayonet-style quartz bulb
Flashtube 12mm flashtube (daylight-balanced and UV-coated
LCD Display Back-lit, high-resolution color LCD. 320x240 pixels; 2.4 in.
Stand Mount Fits stands up to 5/8 in.
Umbrella Mount Accepts umbrella rods up to 9mm
Weight 4 lbs. 5 oz.

[QUOTE=Bob Salomon;1485904]

The flash Randy used. WS, or Joules, is only input. It can not be output.

Output is F stop, GN, ECPS or BCPS. It is never WS!!!

Bob Salomon
25-Feb-2019, 07:58
OK Bob, I used more incorrect terminology. :(

All I can do is read it and try to use in real life. IRL

I did use f stop readings on my Sekonic at the subject distance. I got f22 with both full power strobe and model lamp DEPENDANT upon ISO setting. I shot with recommended TIME with model lamp and used 1/30 sync for both shutters.

Einstein™ Flash Unit
Watt seconds 640 Ws
Power Variability 9 f-stops (full to 1/256 power)
Recycle to Full 1.7 sec.
Flash Duration (t.5) 1/2000 sec. (at full power)
Flash Duration (t.1) - in Action Mode 1/588 sec. (at full power) | 1/13,500 sec. (at 1/256 power)
Flash Duration (t.1) - in Color Mode 1/588 sec. (at full power) | 1/8,000 sec. (at 1/256 power)
Power Requirements Automatic power switching from 95 to 265 VAC, 50/60 Hz (no lamp change or user attention required)
Average Current Draw Brief initial recycle surge current of 8.5A; average draw of 8A
Sync / Trigger Voltage Less than 5 volts (safe for use with DSLR cameras)
Modeling Lamp 250 W, 120VAC bayonet-style quartz bulb
Flashtube 12mm flashtube (daylight-balanced and UV-coated
LCD Display Back-lit, high-resolution color LCD. 320x240 pixels; 2.4 in.
Stand Mount Fits stands up to 5/8 in.
Umbrella Mount Accepts umbrella rods up to 9mm
Weight 4 lbs. 5 oz.

[QUOTE=Bob Salomon;1485909]

But you did not specify reflector type or coverage!
Output will change with these even though your power setting did not change!!

Tin Can
25-Feb-2019, 08:16
Bob,
I did specify reflector by link in post 116 "I just tried measuring 100% model lamp lumens at 1 ft directly in front of the standard reflector with an app https://www.paulcbuff.com/Light-Modi...Reflector.html"

I also posted a setup picture showing the entire set, with the Strobe and reflector illuminating the object.

But you did not specify reflector type or coverage!
Output will change with these even though your power setting did not change!!

tonyowen
25-Feb-2019, 09:28
To: Randy and Bob
Hopefully the below clears the air and reduces the tension

EXPECTED OUTPUT
Full Power (640 Ws) with the 8.5” High-Output Reflector f22 +1/10 at 10 feet (GN 234)
Full Power (640 Ws) with the 11” Long-Throw Reflector f32 +6/10 at 10 feet (GN 394)
Full Power (640 Ws) with a softbox f8 +7/10 at 10 feet (GN 102)
Readings taken at ISO100 in a 14’ x 14’ room with grey walls and floor. For details on expected output readings and measurements takes with other accessories and at other power settings, see our website (www.paulcbuff.com/output.php

regards

Tony

Tin Can
25-Feb-2019, 09:37
No tension here, we are discussing.

I have 2 more 4X5 paper negs loaded. I am trying to find my fastest lens to shoot wide open with the least light output.

Pedalling slowly here. :)

Jac@stafford.net
25-Feb-2019, 15:59
I am sorry I followed this thread so far. The issue seemed so simple to solve by experimenting, but no, it turned into some kinda hopeless ping-pong drama; finally I began to lose my will to live through it.

Randy Moe, you have done more than enough to help. It is time to cut the OP's hook and bait. OP self-help needs promotion here.

Tin Can
25-Feb-2019, 16:20
I have tried to help, and Jac you are right, time to cut bait or fish.

However while doing my second little test 30 minutes ago I had a eureka moment.

I suddenly saw what I have been driving at, which fits an ongoing project.

My time was definetly not wasted!

:)

I am sorry I followed this thread so far. The issue seemed so simple to solve by experimenting, but no, it turned into some kinda hopeless ping-pong drama; finally I began to lose my will to live through it.

Randy Moe, you have done more than enough to help. It is time to cut the OP's hook and bait. OP self-help needs promotion here.

tonyowen
26-Feb-2019, 04:04
The issue seemed so simple to solve by experimenting, but no, it turned into some kinda hopeless ping-pong drama; It is time to cut the OP's hook and bait.

Jac, your expression " hook and bait " has no meaning to me. However, if you have been following the thread then you will have noticed that I have acknowledged the solution several times [ie not enough light]. In addition, the thread took on a life of its own with various side issues.

However while doing my second little test 30 minutes ago I had a eureka moment.

Randy, I definitely do not think you have wasted your time. Query what was your Eureka moment??

regards

Tony

Tin Can
26-Feb-2019, 07:43
Tony,

As previously stated I have almost no experience with paper negatives, yet I do have an obsession with negative prints, perhaps the wrong description. I have completed 2 prints in a series that either include a reversal or are a full reversal by internegative.

One I have posted here before. See below. The second will be shared in the 2019 Print Exchange before it shown to others. Not everyone's cup of tea. I consider them Political Art, yet all art is political in ways we often cannot see.

I previsualized a series that expands on a theme 'seen' in my Eureka moment. I must include a tip of my hat to Sandy King and his interest in exhibiting reversed negative film. I have been exhibiting reversed X-Ray film for some time.

https://farm5.staticflickr.com/4583/38079307405_d44bb3cd9c_b.jpg (https://flic.kr/p/211WpqR)Atomic Bomb (https://flic.kr/p/211WpqR) by TIN CAN COLLEGE (https://www.flickr.com/photos/tincancollege/), on Flickr

Jac, your expression " hook and bait " has no meaning to me. However, if you have been following the thread then you will have noticed that I have acknowledged the solution several times [ie not enough light]. In addition, the thread took on a life of its own with various side issues.

Randy, I definitely do not think you have wasted your time. Query what was your Eureka moment??

regards

Tony

tonyowen
26-Feb-2019, 08:31
Tony,. Not everyone's cup of tea. I consider them Political Art, yet all art is political in ways we often cannot see.I

Randy
Interesting, though I can see what it is, the longer I look the more abstract elements I observe - to the extent that what I see is not what it is.
As stated before many thanks for your input to my question.

regards
Tony