Using electronic flash with LF cameras

[Tin Can]

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.

IMG-2105 by TIN CAN COLLEGE, on Flickr

IMG-2106 by TIN CAN COLLEGE, on Flickr

Page 2 with results in a few minutes.

[Tin Can]

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.



1 D750 1-30sec 1-32power strobe by TIN CAN COLLEGE, on Flickr

2 D750 30 secs 1-32 power 250 watt quartz by TIN CAN COLLEGE, on Flickr

3 paper ISO 4 Full Power Strobe f22 by TIN CAN COLLEGE, on Flickr

4 paper ISO 4 250 watt Quartz 100% f22 by TIN CAN COLLEGE, on Flickr

[tonyowen]

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]

[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]

[QUOTE=tonyowen;1485898]

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]

[QUOTE=Bob Salomon;1485904]

Whose INPUT is 2.5 to 640 WS!!!

Bob that is the advertised adjustable output range. https://www.paulcbuff.com/Flash-Unit...lash-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-Modi...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]

[QUOTE=Bob Salomon;1485904]

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]

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]

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]

[QUOTE=Randy Moe;1485911]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.



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

[Tin Can]

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!!