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77seriesiii
3-Mar-2009, 11:36
so I am new to LF and am using 4x5 Foma 100 (live in Germany so it is inexpensive). We took the camera out yesterday and it was a bumbling affair, no light meter, no watch, only a slight understanding of recip, and then the battery died in our Rollei...All in all an eventful day. with the DSLR we metered a shot for ISO 100, f22 at 15 secs and then my brain started to fry.

I am technical in nature...doing IT for a living and used to fly for the US Army but when I look at Foma's chart:

Schwarzschild effect
Exposure (seconds) 1/1000–1/2 1 10 100
Lengthening of exposure 1x 2x 8x 16x
Correction of aperture number 0 -1 -3 -4

I get that the exposure is a factor of ten but I have no idea how to fill in the blank spaces between 1, 10 and 100 seconds. I have scrounged the forum here and have read quite a bit on outside forums/websites that talk one through reciprocity so I grasp what is going on and why this is an issue but for the life of me I am not having the light bulb moment that will enable me to figure this out on my own.

So I am approaching the forum, with me hat in hand, and am begging someone out there to enlighten me, provide a spark of some sort, so I can get through this and make some reciprocity charts.

Many thanks

Erick

Vaughn
3-Mar-2009, 11:39
How about putting the numbers on a graph and using it to get the in between times?

Vaughn

77seriesiii
3-Mar-2009, 11:46
that would work? for some stupid reason I was hung up that it was a logarithmic curve line...time to make some graph paper or buy it in the morning.

Is it that easy?

Thanks

./e

venchka
3-Mar-2009, 11:53
I can't help your aching head or fill in any blanks except to say that apparently Foma film has terrible recirocity compared to other films. I'm heading out this weekend with my first batch of Foma 200.

Good luck!

Alan Davenport
3-Mar-2009, 12:42
Is it that easy?

Probably. See how the numbers fit on a graph. If it gives a reasonable-looking curve between the known values, you'll be safe enough interpolating.

Wallace_Billingham
3-Mar-2009, 12:58
also keep in mind with photography everything is usally measured in stops and a stop is simply double or half the light of the stop below or above it.

So in looking at your Foma numbers the difference between 10 seconds and 100 seconds is only 1 stop. In the real world (with B&W film anyway) you will not notice much if any difference if you are a stop off.

I use a lot of film from Eastern Europe and for what it is worth I always err on the side of more exposure not less.

photographs42
3-Mar-2009, 13:41
Before you get all bent out of shape over the proper reciprocity compensation, you need to do a lot of calibration of your film and equipment. You have to know what “Normal” is before you can make meaningful adjustments for reciprocity. Even with that knowledge, adjusting your exposure for reciprocity is largely based on judgment.

Your chart states that if your meter tells you to use a 1 second exposure, you need to double that and expose for 2 seconds. At a reading of 10 seconds you need 8x the exposure and at 100 seconds you need to expose 16x. Between these benchmarks you can use graphs or mathematics or you can do what most of us do and make an educated guess. So if your meter indicates say 4 seconds, that’s a little less than half of the difference so I would expose for about 30 seconds. You may think that’s not very precise but keep in mind that my 4 second exposure was based on some very educated guesswork in the first place ( I chose what to meter and what part of the scene to place important values on) and the nature of reciprocity and how it reacts to different parts of the spectrum. Remember, reciprocity causes an increase in contrast because the high values in the scene are affected more by the increased exposure than the low values.

Get a meter; calibrate your film and processing; understand the process and relax and make useful exposures based on educated guesses.

Jerome

photographs42
3-Mar-2009, 13:49
also keep in mind with photography everything is usally measured in stops and a stop is simply double or half the light of the stop below or above it.

So in looking at your Foma numbers the difference between 10 seconds and 100 seconds is only 1 stop.................. ????

I didn’t study NEW MATH but using old math, 10 seconds to 100 seconds is 3 ¼ stops.
Jerome

Paul Kierstead
3-Mar-2009, 14:00
Well, under the new math with reciprocity, it is probably not 3-1/4 stops.

Vaughn
3-Mar-2009, 14:10
Is it that easy?./e

NO... I just tried to graph it several ways with no real luck -- found out I forgotten much of my math and graphing!

I have a list of corrected times for Tri-X that Michale Kenna worked out -- if anyone knows long exposures, he does!

Skipping some of his numbers...(first is metered exposure/second in corrected exposure)

2sec/4sec.....10sec/50sec....40sec/240sec(4.5min)...80sec/630sec(10.5min)...3min/25min
6min/60min...10min/120min...20min/4hours...40min/8hours


Many of my exposures under the redwoods tend to be in the 5 to 30 minute range -- no wonder my shadows tend to drop out sometimes...LOL!

Vaughn

venchka
3-Mar-2009, 14:12
Or we could all just use Fujifilm Neopan 100 Acros. Up to 16 minutes at least.

cjbroadbent
4-Mar-2009, 03:43
Wallace is probably right in the real world of recipricity before TMax. (I am repeating myself, sorry) Once you are over a minute, anything goes; so a sixy second exposure and a sixty minute exposure both look good - but just a little different. I do it with T film and go and have lunch while the film does it's work. Stopping down and shooting long exposures keeps you out of trouble.

Doremus Scudder
4-Mar-2009, 07:06
Erick,

Here is a graph I made in Microsoft Word for Fomapan 100 reciprocity corrections. The values are extrapolated from the (scant) data that is found in the Foma data sheet. The file was too large to upload as a simple Word document, so I've put it in a .zip file

I've changed the values to full stops as they read on the meter to make things easier to apply. Intermediate values can be estimated. These are not exact, but within a fraction of a stop (i.e., close enough).

Hope this helps

Doremus Scudder

Vlad Soare
4-Mar-2009, 08:16
Erick,

For Fomapan 100 I use the attached table, which I compiled myself based on the technical datasheet of the film. I've printed it on a small piece of paper and keep it in my camera case.
So far I have only needed and have only used the corrections for 8 seconds, 15 seconds and 1 minute. All of them proved to be correct.

I hope this helps. :)

77seriesiii
4-Mar-2009, 10:08
Vlad/Doremus; Thank you both for the reciprocity charts! I am going to make my own and then compare the two and see how I did and knowing me print all three and place them in a spot I'll forget about. :D

I'm pretty excited about using this film, having used a smaller cousin (efke 120) souped in Rodinal and really liked the results. Even better news my package of Pyrocat HD arrived today (powder form), now all I have to do is expose some, make a few test shots (only have to do this once as a friend stated) and go from there.

pretty stoked, wish I had time tonight to go play

Thanks again to all who helped clear the mystery. My path is clear but for some reason it goes into the shadows!

./e

Wallace_Billingham
4-Mar-2009, 10:20
I didn’t study NEW MATH but using old math, 10 seconds to 100 seconds is 3 ¼ stops.
Jerome

yes but that is the meter reading and NOT the multiple for reciprocty faliure

for example if the meter reading is 10 seconds you have a multiple of 8x or 80 seconds. If you used the next multiple of 16x that would give 160 seconds or exactly one stop more than 80 seconds. Either way you will be fine.

Or if your meter gave you a reading of 100 seconds at f/22 for example you could easily shoot for 800 seconds (about 13.5 minutes) at f/22 or 1600 seconds (about 27 minutes) or even f/22 for about an hour and pretty much get the same results since you are only a stop off. Pretty much any exposure from 15-60 minutes would work out with very printable negatives

No new math is needed just a basic understanding of long exposures of which I do quite a bit. Lots of times I go fishing along streams as the sun is going down, I set up my camera for a good shot on a tripod, open the shutter and come back 15 minutes to an hour later while I fish. Works very well

mandoman7
4-Mar-2009, 11:16
Vlad/Doremus; ... now all I have to do is expose some, make a few test shots (only have to do this once as a friend stated) and go from there.
./e

Be careful of the desire to use your new toys before you've fully calibrated things. One test run will only give you a ballpark estimate of your best development numbers. My preference is to really nail the development time with a testing procedure that uses objective measurements (x-rite). That way, I can shoot with confidence that one variable has been isolated.
Reciprocity can be tested for also. Be skeptical about the numbers from charts or from people who's work methods you don't know. Those are figures from which one starts their tests. Its not just exposure, but also contrast and the overall look of the results that you are working towards. Be sure and ask yourself what you are trying to do.

JY

Doremus Scudder
5-Mar-2009, 08:48
Mandoman7,

I agree that one should nail down personal E.I. and developing time.

My table was based on the reciprocity data from the manufacturer and, assuming it is correct, should work well once the personal E.I. and developing time is determined. The reciprocity response characteristics of the film is dependent on exposure time/amount of light, and not any particular E.I. Of course, if one is shooting way off as far as E.I. goes, the reciprocity compensation could be off by a bit, but usually not more than a stop or so: the negs would still be in the ballpark.

One thing we haven't discussed here is altering development to compensate for the increased contrast caused by reciprocity failure. Generally speaking, the more reciprocity correction necessary, the greater the increase in negative contrast for a given development time. I use a rule of thumb that assumes a reduction in development time of approx. 10% for each doubling of the indicated time, i.e. indicated time is 10 sec., given is 80 sec. = approx. 3 doublings and a decrease in development time of 30% (10 doubled is 20; 20 doubled is 40; 40 doubled is 80 = 3 doublings).

Normally I just round the developing time to the nearest step in the Zone System (e.g. my N-1 is about 25% less time than my N. A one-doubling neg would only get a 10% reduction, so I would just develop it N and deal with the bit of extra contrast in printing. A two-doubling neg is 20% reduction, so I would develop it N-1, etc.). Of course, everyone should refine the development compensation for their particular situation.

Best,

Doremus Scudder

Roger Vadim
5-Mar-2009, 16:45
doremus and vlad: thanks for the tables, I am also fiddling with Foma 100 and these charts look really helpfull. Greatly appreciated!
Michael

mandoman7
5-Mar-2009, 19:28
Mandoman7,

I agree that one should nail down personal E.I. and developing time.

My table was based on the reciprocity data from the manufacturer and, assuming it is correct, should work well once the personal E.I. and developing time is determined. The reciprocity response characteristics of the film is dependent on exposure time/amount of light, and not any particular E.I. Of course, if one is shooting way off as far as E.I. goes, the reciprocity compensation could be off by a bit, but usually not more than a stop or so: the negs would still be in the ballpark.

One thing we haven't discussed here is altering development to compensate for the increased contrast caused by reciprocity failure. Generally speaking, the more reciprocity correction necessary, the greater the increase in negative contrast for a given development time. I use a rule of thumb that assumes a reduction in development time of approx. 10% for each doubling of the indicated time, i.e. indicated time is 10 sec., given is 80 sec. = approx. 3 doublings and a decrease in development time of 30% (10 doubled is 20; 20 doubled is 40; 40 doubled is 80 = 3 doublings).

Normally I just round the developing time to the nearest step in the Zone System (e.g. my N-1 is about 25% less time than my N. A one-doubling neg would only get a 10% reduction, so I would just develop it N and deal with the bit of extra contrast in printing. A two-doubling neg is 20% reduction, so I would develop it N-1, etc.). Of course, everyone should refine the development compensation for their particular situation.

Best,

Doremus Scudder

The reciprocity effect and its increasing contrast can also be used as a tool, not necessarily something to compensate for. I had a project that went on for a while where things dropping off into black was part of the composition, and the exposure was lengthened as needed to encourage that effect.
Anyway, good luck with your explorations.
JY

ki6mf
6-Mar-2009, 10:18
At New England School of Photography we use this table as a starting place for black and white. I think that HP 5, the only film i shoot, can handle a 1 second exposure without going to the table. You should test to be sure.


Meter Reading Increase Time to:
1 Second 2 Seconds
2 Seconds 4 Seconds
4 Seconds 10 Seconds
8 Seconds 25 Seconds
15 Seconds 1 Minute 10 Seconds
30 Seconds 3 Minutes 10 Seconds
1 Minute 9 Minutes
2 Minute 22 Minutes
4 Minute 48 Minutes
8 Minute 1 Hour 30 Minutes
__________________
Wally Brooks

Everything is Analog!

Doremus Scudder
7-Mar-2009, 04:18
Mandoman7,

We're getting a bit off-topic here, but you bring up an interesting point about using reciprocity failure intentionally. I often use the contrast increase achieved by long exposures instead of expansion developing. I think it has a different character. Stopping down to get a longer exposure time or using a neutral-density filter can get you into the three-doubling range, which gives you about N+1 at normal developing times.

Wally,

The table you give seems to be for a different film than the FOMA 100. Using these times for the Foma film would likely underexpose. Each film has it's own reciprocity characteristics; one cannot reliably apply data from one film to another.

Best to all,

Doremus Scudder

mandoman7
7-Mar-2009, 07:47
Mandoman7,
I often use the contrast increase achieved by long exposures instead of expansion developing. I think it has a different character.
Best to all,

Doremus Scudder

Agreed. You can keep the mid and high tones in their proper relationship while completely dropping out the dark areas. Very useful in some contexts.

JY

77seriesiii
8-Mar-2009, 03:46
Mandoman7,

your comment falls in line with where I am going with trying to understand reciprocity. I understand what you are saying with testing and eliminating/identifying most idiosyncrasies of the film used, in my case the fomapan 100. Once a solid understanding of how it reacts in the reciprocity range and using consistent developing techniques (same developer otherwise another variable is introduced) I can exploit reciprocity and use the behavior to create something. I dont know what something is but when I create it more than once consistently and intentionally than it could be something. :)

./e