Severe manipulation of film curve

[reggie]

This is probably impossible, but I'll ask anyway....

Is it possible to increase the slope of the mid-section of a film's characteristic curve and leave the toe and shoulder relatively unaffected? I would essentially like to create an outward 'bulge' in the normally straight-line section of the characteristic curve.

Thanks.

-R

 

[David A. Goldfarb]

There might be a way to achieve that kind of effect with contrast masking.

I was looking at some platinum prints by Cy DeCosse recently, and he uses multi-layer masks to improve separation in different parts of the curve.

 

[reggie]

That did occur to me, but I was wondering if there was a way to do it in the negative in processing and avoid the extra work in printing.

-R

 

[David A. Goldfarb]

Local bleaching?

 

[reggie]

Local bleaching?

How about overdevelop the negative to get the mid-values up and then treat the negative with a reducer that affects dense areas first. This may bring the shoulder down to 'normal' densities for Zone IX and VIII without affecting sones IV thru VII. I wonder if that would work. I have never used a proportional reducer before.

How do you locally bleach a negative? Or did you mean the print? I have done a lot of local bleaching on prints and that works fine but I don't think it's a replacement for proper densities in the negative in the first place.

-R

 

[David A. Goldfarb]

You can locally bleach a neg the same way you do a print--hypo, potassium ferricyanide with a brush, rinse, back in the hypo, repeat until it looks good.

You can also locally intensify with selenium toner 1:3 or so and a brush or cotton swab. Ansel Adams discusses this technique on "Moonrise," if I remember correctly.

Overdeveloping and reducing the whole neg, I'd worry about losing the shadows, but I haven't tried proportional reducers either. There's one in Anchell's _Darkroom Cookbook_ that is supposed to reduce the highlights and midtones without disturbing the shadows, so maybe that's an answer.

You could also try going the other way and underdeveloping and using an intensifier like selenium, though in my experience, that just pushes up the highlights without doing too much for the midtones.

 

[Photo Engineer]

I believe that a film that has a limited tone scale or limited maxiumum density can be over developed such that the mid scale will bulge 'upwards' while leaving the upper scale unaffected much due to the limit imposed on it by its maximum density. However, the effect on the toe may be different than desired. Usually, the toe will sharpen.

Only tests will confirm whether is possible.

T-grain film and K-grain film will respond differently, and the number of emulsion components will also cause the films to behave differently.

A K-grain film is more likely to behave as described in the first paragraph, IIRC, whereas a blended t-grain film may behave that way only if you can affect the mid speed component.

Good luck to you.

PE

 

[reggie]

Any suggestions on specific films to try out first? I have noticed the published curves for EFKE 100 show a strong propensity to rapidly build mid-tone and highlight density with increased dev times, while holding the toe very well. I have not personally plotted any curves for this film, but it looks like a promising candidate.

Underexposing a little might help keep the toe down if necessary.

-R

 

[Donald Miller]

Any suggestions on specific films to try out first? I have noticed the published curves for EFKE 100 show a strong propensity to rapidly build mid-tone and highlight density with increased dev times, while holding the toe very well. I have not personally plotted any curves for this film, but it looks like a promising candidate.

Underexposing a little might help keep the toe down if necessary.

-R

My experience with Efke Pl 100 does indicate a great degree of expansion capability...by the same token underexposing by too much and it won't do much in building density at all.

I wonder what would happen with an unusual film like Freestyle APHS (graphics film) ...it is cheap as dirt, comes in a lot of different sizes and builds a lot of density range if required. Jim Galli uses it a lot for pictorial use from what I understand.

I have used it for masking but have no in camera experience with it.

I don't see where masking would be of any help with what you are wanting to do. The only masking would be something like a first generation contrast reduction mask to collapse the shadows in a situation where you developed to a higher then normal DR. Taking it a step further a second generation contrast reduction mask would collapse the highlights while holding everything else...

I think that both masks used in conjunction would probably accomplish what you want.

 

[Kirk Keyes]

Reggie - Do you mean to do this so much that you get a solarizing effect or to just build contrast in the midscale while flattening out the highlights?

If the first one, then masking would be the way.

If it is the second one, then you could try a staining film developer and then print on VC paper. Perhaps overdeveloping some to increase the midscale caontrast and also build more stain in the highlights. The VC paper will print the highlights with less contrast than the less-stained midscale tones.

Kirk - www.keyesphoto.com

 

[Ole]

I'm sure you can do just about anything by combining different bleaches and toners. There are plenty of recipes for "Cutting", "Proportional" and "Super-proportional" bleached (reducers), and toners which can do anything you want (and more) to the tonality.