Finding a proportional reducer

[DrPablo]

I'm trying to find a proportional reducer to thin the dense highlights of an extremely contrasty negative. I've searched around here and found the RA4 Bleach-Fix recommended, but I can't find any except in 4 liter quantities. I can do a little bit of mixing, though I don't want to accumulate a lot of bulk chemicals I don't use very often.

 

[Ryuji]

It doesn't have to be blix. Just bleach will do, if you can find one. You just have to fix the negative right after.

RA4 bleach is a weaker bleach and (for a different reason) environmentally less harmful than ferricyanide bleach, but the bleaching mechanism is very similar between the two. Blix is a bit weaker than straight ferricyanide bleach. One way you can make the classic ferri bleach milder is to bleach a bunch of test prints in a tray and then use for what you need to do. A standard trick to do the same in lab is to mix ferrocyanide, but a few black test prints will do... until you notice that the bleach acts slower and more mildly.

However, for a dense negative, I generally recommend to preflash the paper than bleaching the negative. By bleaching the neg, you'll lose quite a bit of shadow details. Another way is to scan the neg with a very good film scanner and adjust the curve in an image editor.

 

[Dhar]

Have you looked at the Formulary?

"FORMULARY REDUCER 1 FOR NEGATIVES is a hypo-potassium ferricyanide negative reducer, which is similar to both Kodak R-4a and Kodak R-4b."

Sounds like what you're looking for, and only 1 liter.

-g.

 

[DrPablo]

Will the ferricyanide in cyanotyping solution work? I have the Photographer's Formulary pre-mixed solution, and I think one of them is actually potassium ferricyanide.

I don't want to preflash the paper, because I want the highlights to remain white. The problem is that the image as a whole really needs to be developed at high contrast, but there are some parts that are so dense that I need serious burning (and about 8 million test prints) to get it how I want it.

Part of my motivation to bleach the negative is so that I can use it for alternative processes. I suppose I could pre-flash the coated paper as well.

"FORMULARY REDUCER 1 FOR NEGATIVES is a hypo-potassium ferricyanide negative reducer, which is similar to both Kodak R-4a and Kodak R-4b."

Sounds like what you're looking for, and only 1 liter.

Thanks for the link, Gary. I'm a bit confused -- they describe a proportional reducer as equally affecting highlights and shadows, whereas I thought "cutting" reducers would apply equally to the whole image. A proportional reducer, in my understanding, disproportionally reduces the areas of highest density.

 

[Dhar]

Thanks for the link, Gary. I'm a bit confused -- they describe a proportional reducer as equally affecting highlights and shadows, whereas I thought "cutting" reducers would apply equally to the whole image. A proportional reducer, in my understanding, disproportionally reduces the areas of highest density.

Good (and confusing) point. I've not had the opportunity to use any reducers, so I'm not the guy to ask on this. I was going on their description of it being similar to RA-4.

In fact, googling around for information on cutting, proportional, sub, and super...I can't find a good, definitive answer to which does what. Perhaps someone more knowledgeable about the differences will weigh in.

-g.

 

[Ole]

Let's see...

If we take the silver amount in the image and assign it values from 0 to 100%, then - we're all going to get confused. Lets set it at 0 to 100 arbitrary units instead!

A proportional reducer cuts the same proportion of silver from all values - say 10% of the existing silver regardless of original content.
That means that everything will be a bit lighter - it's just like you had developed a bit less.

A cutting reducer cuts the same amount from everything - e.g. 10 of our "arbitrary units". So where you had 100 this also gives 90, but where you had 10 you now have 0, and not 9 as with a proportional reducer.

Then there's the superproportional, which preferentially reduces the densest bits, changing not only the slope but also inducing a curvature in the tone curve. That could be a reducer which still reduces our 10 to 9, but might take our 100 down to 60, and 50 down to 40.

Like everything else in photographic chemistry it's really a lot more complex than this. But this is close enough to Eder's (sr.) explanation of a century ago that it should still be reasonably correct.

 

[Dhar]

Thanks, Ole. I think it was the use of the word "proportional" that had me puzzled. Much clearer, now!

-g.

 

[dancqu]

The problem is that the image as a whole
really needs to be developed at high contrast,
but there are some parts that are so dense ...

A perfect candidate for SLIMT. Leave the negative alone.
Print on Grade 4. Using an extremely dilute P. ferricyanide
+ a little bromide solution bleach the paper's latent image.

Read David Kachel's article "Variable Contrast From
Graded Papers". Dan

 

[DrPablo]

Wow, that's a cool technique. I've only skimmed it so far, but I take it the idea would be to expose such that the densest part of the negative is normally exposed, then bleach, then develop.

The one thing that leaves, though, is non-silver printing, for instance getting a cyanotype from this image.

 

[dancqu]

[QUOTES=DrPablo;445749]
"Wow, that's a cool technique. I've only skimmed it so far,
but I take it the idea would be to expose such that the
densest part of the negative is normally exposed, then
bleach, then develop."


IIRC, some additional exposure is needed. Likely due to
some bleaching of latent image in highlight areas. The
bleach is disproportional affecting the most exposed
areas of the paper more so.


"The one thing that leaves, though, is non-silver printing,
for instance getting a cyanotype from this image."

No surprise. At www.unblinkingeye.com are two articles
which describe methods that may solve any contrast problem.
Select Articles and search the sectioned articles list
for; Latent Image Bleaching and Less is More. Dan