B&W Reversal: contrast

[gioffry]

Hi huys,
has anyone ever tried to add sulfuric acid to the second development (in B&W inversion treatment) to reduce film contrast?

If so, what doses?

Thank you!

 

[Anon Ymous]

No, I haven't and doesn't sound like a good idea IMHO. Contrast adjustment should better be done in the first development.

 

[Europan]

No, haven’t. Why should one add a mineral acid to a developing bath? It only brings down the pH value, the developer’s activity and integrity, and destroys the following fixing bath. Sick idea

 

[gioffry]

Sulfuric acid significantly reduces the DMAX value. Do you have a better idea to reduce the final contrast?

 

[Ian Grant]

Contrast is usually controlled by choice of first developer. However some very early cine-reversal processes also controlled contrast and Dmax by the length of the re-exposure and development time.

You could use a soft working developer like ID-3/D165 as the second developer.

Ian

 

[gioffry]

thank u Ian Grant

 

[Rudeofus]

If you take a look at how reversal image tones are created:

• the toe region (i.e. the region with the weakest exposure which holds shadow detail) will keep lots of Silver Bromide/Iodide after bleach and will therefore become the darkest region of your slide
• the shoulder region (i.e. the strongly exposed parts) will keep very little Silver Bromide/Iodide after bleach and therefore turn into your highlight region

If you weaken FD development, either by making FD less active, or by shortening FD time, you will move the toe region towards stronger exposures and the shoulder region towards much stronger exposures. As a result you need to expose more to get visible shadow detail, and contrast goes down, i.e. much higher exposure is necessary for clear highlights.

If you weaken SD development, you may clear some highlights which had some density before, and you will lose lots of density in shadow region. While this is certainly a way towards reducing contrast, this is not necessarily going to give you nice slides. Typically people want the full tonal range in images. Adding acid (any acid will work, you don't have to use Sulfuric Acid) to SD is one of the many ways to reduce SD activity.

For these reasons most people would adjust contrast by changing FD, but it depends entirely on your intended result which path you chose.

 

[gioffry]

Really thank you very much for your thorough reply!!!

I've 2 questions:

1)

If you weaken FD development, either by making FD less active, or by shortening FD time, you will move the toe region towards stronger exposures and the shoulder region towards much stronger exposures. As a result you need to expose more to get visible shadow detail, and contrast goes down, i.e. much higher exposure is necessary for clear highlights.

(Exposure N+1) + (FD N-1) = the contrast goes down
Did I get it right? if so, is there a risk of having gray whites?

2)

Adding acid (any acid will work, you don't have to use Sulfuric Acid) to SD is one of the many ways to reduce SD activity.

For example? What other acid?

 

[Rudeofus]

I've 2 questions:
1)(Exposure N+1) + (FD N-1) = the contrast goes down
Did I get it right? if so, is there a risk of having gray whites?

Yes, that would likely work. There is no guarantee about gray whites or gray blacks, since there is no standardized development regime like with E6. If you want to deviate from established procedure, then you will have to do some test slides to determine your procedure for the results you are after. There are basic principles, like "adding solvent to FD or raising its pH increases activity" or "cutting SD time short or reducing SD activity will reduce Dmax", but there are AFAIK no published numbers for B&W slides comparable to massive dev chart for negative development.

2) For example? What other acid?

Acetic Acid (aka white vinegar) or Citric Acid (aka E330) are very easy to get, and both will work well. If a reduction of developer activity is what you are after, you may even get away with just diluting the developer with water.

 

[gioffry]

VERY THANKS !

 

[twelvetone12]

Are you going to reverse P30? (I lurked you blog , very nice!!)

 

[gioffry]

Are you going to reverse P30? (I lurked you blog , very nice!!)

Ok, fine, you got me