Reciprocity In Development

Bruce Osgood · Sep 21, 2006

I shot some 4x5 film today at reciprocity adjusted exposures longer than 1 minute but less than 10. The film is FP 4+ and I will be using P-cat HD with Jobo rotation. All SBR's were at or under 3.

What kind of reciprocity in development might you suggest,

Thanks,

noseoil · Sep 22, 2006

Bruce, the reciprocity resides in the film, not the development. By SBR's of 3 and less, do you mean 8 (example: EV 7-4=3 which means 3+5 or 8)? I think I may be a bit confused about the question. tim

Bruce Osgood · Sep 22, 2006

noseoil said:
Bruce, the reciprocity resides in the film, not the development. By SBR's of 3 and less, do you mean 8 (example: EV 7-4=3 which means 3+5 or 8)? I think I may be a bit confused about the question.
tim

Thanks Tim, perhaps I am confused.... (not new). I thought that a negative receiving longer than 1 second exposure (reciprocity adjusted), (Say a neg meters at 1 sec, you would give it 2). That neg at development needs to be adjusted further to compensate for the over exposure on the film, usually by a minus development. Could be I'm wrong about this.

SBR. I'm not that familiar/experienced with the SBR technique and have usually metered Zone III or IV and shot from there. My meaning when I wrote was an SBR of 7-4 = 3; 7-5 = 2. I forgot to add the 5 inherent in the film. But this would have given me SBR's of 8 and 7, still representing minus development, but not to the degree I thought. Am I wrong about this too?

reellis67 · Sep 22, 2006

I've heard that too, but I don't do it and my results seem fine. I've been looking for a reliable reference stating that development needs to be adjusted (as opposed to 'net rumor) but I've not yet found one. If anyone has one, I'd be interesting in hearing about it.

- Randy

Neal · Sep 22, 2006

Dear Bruce,

Kodak suggests a 20% to 30% reduction in development time for Plus-X in your exposure range. My guess is that with such a flat scene and VC paper you could safely ignore development modification.

Neal Wydra

juan · Sep 22, 2006

SBR 7 is normal development - 8 would be only slightly minus, probably less than N-1 in ZS terminology. I'd agree with Neal and ignore development modification.
juan

noseoil · Sep 22, 2006

Bruce, I would do 2 shots of identical exposure. Pick the time you think is correct, then do a print from it. If the development seems right, plot it on graph paper. I use the y axis on the left for sbr and the x axis on the bottom as a time line.

If your development was off the first time, try another interval (pick something easy to plot) and do a print. This is not too scientific, but you can do pretty well with this method. It allows you to build on past shots for your data. Best, tim

Jim Noel · Sep 23, 2006

A lot depends on how you print the negatives.
If you use variable contrast paper a change in filtration should take care of the extra contrast built up through long exposures up to a point.
I don't use VC papera very often so I do have to pay attention to added contrast caused by longer exposures. I do not make any changes in development until my exposures get over one minute, which is frequent. Then I follow the recommendations for reduced development to keep the highlights from blowing out.

Photo Engineer · Sep 23, 2006

I've been discussing this thread offline with Oskar Ojala, and he has remided me that Ansel Adams wrote about this. Adams took it from Kodak publication F-5.

As you increase exposure, to compensate for reciprocity, the contrast of films often goes down. To correct for this, you increase development time to get back to the desired contrast. It would take tests to determine this for each film, as they respond differntly. With some films, contrast may go up requiring a decrease in development time.

Oskar has also reminded me that this may not be true for many modern films.

I had forgotten a lot of this, but Oskar refreshed my memory on the subject of adjusting development for contrast reciprocity reasons.

So, my thanks to Oskar.

PE

Oskar Ojala · Sep 23, 2006

Photo Engineer said:
I've been discussing this thread offline with As you increase exposure, to compensate for reciprocity, the contrast of films often goes down. To correct for this, you increase development time to get back to the desired contrast. It would take tests to determine this for each film, as they respond differntly.
PE

Sorry, I remembered it wrong from the top of my head. It goes the other way around, i.e. increasing exposure increases contrast. the F-5 table goes like this:

indicated exp. real exp. dev. change
1 2 -10%
10 50 -20%
100 1200 -30%

But please check the details for the specific films you're using, this info is 25 years old and probably doesn't apply for T-grain films!

Helen B · Sep 23, 2006

Low intensity reciprocity failure hits the lower intensity regions of the image more than the higher, so the contrast generally rises, hence the suggested decrease in development.

Best,
Helen

Photo Engineer · Sep 23, 2006

Helen B said:
Low intensity reciprocity failure hits the lower intensity regions of the image more than the higher, so the contrast generally rises, hence the suggested decrease in development.

Best,
Helen

Helen;

You are right, but I have seen it go both ways. It depends on the emulsion. That is why I suggest tests for each emulsion and exposure time. With blended emulsion it can even create humps and bumps in the charateristic curve as each component responds differently to the exposure conditions.

PE

Lee L · Sep 24, 2006

Here's my reasoning on the way reciprocity failure causes increased contrast:
(there was a url link here which no longer exists)

This effect would require the reduced development often recommended by Kodak and others to hold a normal contrast scene to a normal density range in the negative.

Lee

Photo Engineer · Sep 25, 2006

Lee, you and Helen are both right but with qualifications.

The toe is losing speed more rapidly than the shoulder, and so contrast goes up (in most cases), but imagine a film made of a blend of 2 emulsions. If the toe of both lose more speed, then you see higher contrast in the low density regions and lower contrast in the higher (mid scale) regions due to speed loss of the second component toe speed loss.

I know that this is a complex argument, but the result is higher contrast, normal contrast lower contrast normal contrast as you measure the curve, and the result is a bumpy curve. I have run into this building C41 films. They have 3 components in each layer.

The solution is to solve the reciprocity failure problem as much as you can, and that has been done in most modern EK films. In fact, it has been solved in most modern films.

Also, this assumes a 'straight' emulsion. I have seen emulsions which behave in the opposite direction due to other reasons such as spectral sensitivity and finish, and I have seen graded iodide emulsions which behave in a peculiar fashion as well. So, there is a general rule to use, but I would suggest individual tests on each film to be sure of the amount of change in speed, contrast and in the direction of change.

PE

gainer · Sep 25, 2006

Howard Bond, in an article for Photo Techniques, did extensive tests of reciprocity for a number of Kodak and Ilford films and found results that were much different from recommendations of both manufacturers. Howard was very meticulous in his experiments and reported his experimental plan and methods as well as results. He found little if any change from normal contrast, hence little if any change from normal development time.

Photo Engineer · Sep 25, 2006

gainer said:
Howard Bond, in an article for Photo Techniques, did extensive tests of reciprocity for a number of Kodak and Ilford films and found results that were much different from recommendations of both manufacturers. Howard was very meticulous in his experiments and reported his experimental plan and methods as well as results. He found little if any change from normal contrast, hence little if any change from normal development time.

Patrick, you are correct and this only verifies what I said. You should run your own tests.

The data on Kodak's web site is old, but the films have been improved as I mentioned above. They are often blends of 3 emulsions and must be modified to prevent those bumps from taking place at varying exposure times, therefore reciprocity was improved with no change to the 'generic' instructions given by Kodak, and most people were following outdated instructions.

Use of new chemicals and techniques has done much of this.

Beware though, as not all films have been improved.

PE

Reciprocity In Development

Bruce Osgood

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noseoil

Bruce Osgood

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reellis67

Neal

juan

noseoil

Jim Noel

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Oskar Ojala

Helen B

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Lee L

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gainer

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Reciprocity In Development

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