developing times for long exposures

[Jean Nightingale]

Hello everyone,
I have taken alot of shots in Durham cathedral with exposures usually running at 2.30 min. I now want to know my normal develpoment time. I am using Rodinal film developer at 1:25. Normal it says for this is 8min. If I run a set of tests as described in books,ie pulling film out at 30secs difference in time, on blank VIII eposures, to find my usable white, this I understand. However will this Normal Time I then discover be still relevent for my extended exposure film. (the books I read say reduced development to compensate for the added reciprocity time).
Jean

[steve simmons]

Shortening dev time to compensate for long exposures depends on the film, not the developer. With Kodak films you should probably decrease your dev time about 10-15% as a starter. With Ilford films maybe 5%.

What you have not told us is some very important info

1. what was the contrast range in the scene? Was it N, N-1, N-2, ???
2. how did you determine your exposure and did you compensate for reciprocity failure

My favorite film for this type of treatment is Tri-X

steve simmons
View Camera, The Only Magazine for the Large Format Photographer
www.viewcamera.com

[Bruce Watson]

The problem with long exposures is reciprocity effects. Each film type reacts differently.

The real problem comes when parts of the scene are bright enough so that part of the film does not go into reciprocity, while other parts are dim enough that that part of the film does go into reciprocity. To get good exposure in the shadows you end up over exposing the highlights, sometimes by quite a bit. This tends to result in artificially increased contrast of the scene. Sometimes this increase can be quite large.

The old adage of "expose for the shadows and develop for the highlights" still applies. In this case you end up cutting development time, going to stand or semi-stand development, etc. all in an attempt to lessen density in your highlights. So basically, the books you are reading are correct.

One interesting technique to handle this is to use neutral density filters to dramatically increase exposures -- thus pushing the entire sheet of film into reciprocity. Really long exposures have the added "benefit" of making all the people and animals "disappear" because they don't stay in the frame long enough to register. This may not be what you want however; clearly YMMV.

Another idea would be to use a film that has really good reciprocity characteristics, such as 400Tmax. You might also want to consider a different developer for the more modern films to get more real film speed out of the film.

[Jean Nightingale]

Thank you for your replies. I was using HP5+ 400 rated at 320.My exposures to get detail in the shadow and ensure a good depth of field were often something like 30secs at f32. Using Steve Simmons reciprocity chart this gave me 2.25min exposures. This is slow enough to make the people disappear which is what I wanted. I have a variety of ranges in the shots which I noted, knowing I would need this info for development. What I therefore
need to know now is Normal developmental time for HP5+ 400 in Rodinal 1:25.This would then help me to work out my +1 and -1 developmental times. Would the best way to do this be to find some darkened scene with a range of 5, between low and highlight, and shoot it a few times. I could then pull them out at various times and see which is best?
Jean

[steve simmons]

Did you do these photos without testing for your EI and dev time beforehand???

What was the contrast. You are still not giving us enough info to really help you.

steve simmons

[Jean Nightingale]

Steve, I tried to do EI beforehand but got in a bit of a mess because the card was lit, i discovered, slightly unevenly, but from what I could experience from previous shots I reckoned 400 for film speed was a bit optimistic therefore I set my spot meter at 320. The contrast range for my shots in the cathedral varied. some had 5 zones difference, some less and some more. I did keep notes on each shot.The ones I am concerned about are some with 8 zones difference. I know I should reduce development for these, but I am unsure as to how much less. In your book you suggest -14% for metered exposures of 32 secs.Do you then reduce again to contain the contrast? I am learning this all from reading and trying it out, but I would like to get it right.
Jean

[steve simmons]

Correcting dev time for reciprocity failure and for contrast reduction are different. With Ilford films I make very little dev time reduction for RF. Do some testng and find a normal time. Then try and figure for plussing and minussing.

There is a good and simple procedure in the Free Articles section of the View Camera web site

www.viewcamera.com


steve