Any way to significantly increase contrast with RA4?

[max_ebb]

Is there anything I could add to the developer? I have some abstract imagery on negative film that would look better with more contrast (significantly more), and I was hoping there was some technique that would let me accomplish that.

I tried decreasing the exposure and increasing the develop time, and didn't see any notable increase in contrast, but I only decreased the exposure by 1/8, and I only increased the develop time by a few seconds. If I drastically decrease the exposure time and drastically increase the develop time, would it cause a significant increase in contrast? I was going to just try it and see, but I figured I'd ask here before I waste paper and chemistry.

Thanks in advance for any help on this subject.

 

[David A. Goldfarb]

I haven't tried it with color neg, but I suppose you could make a contrast increasing mask. You would do this by contact printing a positive mask on a panchromatic B&W film, and contact printing that to another sheet of film (panchromatic or ortho) and printing it in register with the original neg.

 

[Photo Engineer]

There are 4 ways to increase contrast with RA4.

1. Develop, fix, wash, rehal bleach, wash, redevelop and etc until the desired contrast is obtained. Lights go on after the first fix.

2. Developer + 10 ml / L hydrogen peroxide. Process normally.

3. #1 but in second developer add hydrogen peroxide as in #2

4. #2 but use cobalt hexammine chloride.

PE

 

[max_ebb]

Photo Engineer, thanks for the info on adding hydrogen peroxide. I assume you're referring to the regular drug store variety 3% hydrogen peroxide? How much does that increase the contrast? If I wanted more increase in contrast, could I up the amount of H2O2 to 15ml/l instead of 10? Of course I will experiment with it, but I'm kind of curious to know what to expect.

 

[Photo Engineer]

Contrast increases continually with time of treatment. There are patents under my name and Vern Bissonette at EK on the peroxide and cobalt treatments.

You have to play with it sometimes and color balance shifts. I get 1 - 2 contrast grades.

PE

 

[max_ebb]

Contrast increases continually with time of treatment.

Does that mean I would get more increase in contrast with room temperature processing (with longer develop time) than with 95° processing with shorter develop time? I do drum processing in a temperature control bath, and I usually process at 95°. Should I process at a lower temperature for a longer develop time if I'm going to use H2O2?

 

[Photo Engineer]

The results vary. Remember that this is 'experimental' so you have to find your own conditions. Since the subject matter is low in contrast, I cannot say what would be best for you.

Since some of these can be done in the light, such as the rehal process, you can do it by inspection. That should help.

PE

 

[max_ebb]

Photo Engineer;

Thanks loads for the H2O2 tip. I did some prints tonight (well actually last night since it's past midnight) and the results using H2O2 were better than I hoped for. It made prints that were otherwise slightly 'muddy' looking really perk up with higher contrast and better color saturation.

Processing at 95°, I used about 12ml/l H2O2 for moderate increase in contrast, and about 20ml/l for a significant boost (kind of like the old r3000 reversal process from transparencies, but without the totally blown out high lights). For the particular images I used it for, it was just the ticket.

Thanks again.

 

[Photo Engineer]

I'm glad it worked well for you. What paper did you use? Did you have to change the filter pack?

The last time I tried it was with Supra III and I had a distinct magenta bias is why I ask.

PE

 

[max_ebb]

I'm using Ultra right now. I got a very slight shift toward magenta. I didn't notice any shift at all when I first printed them, but when I did direct comparisons this morning with prints I printed previously, I could detect a very slight shift toward magenta (barely discernible). These are abstract images, so color balance isn't critical like it would be with wedding formals or something like that.

What processing method/temperature were you using when you got a distinct magenta bias? I drum processed at 95°, and I added the hydrogen peroxide to the developer right before I dumped it into the drum (I added the hydrogen peroxide while the print was getting pre-wash). I wonder if the color shift would have been worse if the hydrogen peroxide had been mixed with the developer for a longer period of time before the print was processed.

 

[Photo Engineer]

I added the H2O2 before processing, and I used a tray process at 68 degrees F. So what I did is not representative.

PE