what happens to anti-halation in long pre-soaks?

[djkloss]

I've been experimenting with longer (5 minute) pre-soaks and it seems to remove all the dye. I was wondering if there are any negative side effects to doing this. What is the purpose of anti-halation layer? Is it the same thing as dye?

I leave my film sit for 5 minutes (rapping once initially to remove air bubbles), and the water comes out like Welch's grape juice.

Thanks!

Dorothy

 

[Andy K]

The anti-halation layer stops light passing all the way through the film. Without this layer light would travel through the film and then reflect back off the pressure plate (in a 35mm camera) creating halation (or a glow) around bright areas of the negative.

 

[Gerald Koch]

Once the film has been exposed the antihalation layer no longer serves a useful purpose. If the only purpose of your longer pre-soaks is to remove this dye then you are wasting your time as it will be removed in the developer just as well.

 

[Robert Hall]

The light would reflect off of other halides as well, so it's not entirely a pressure plate issue, but essentially, that is the gist.

A longer presoak isn’t necessary for the antihalation dye. It should be removed completely as the other chemicals pass over the film. It has not effect on the effectiveness of developers and the like.

The one thing a presoak does give is a uniformity of the gelatin and will aid in give you even development. I presoak film from 2 to 5 minutes. The larger the film, the longer I soak. It's just a little insurance on getting even development when I have 40+ sq inches of sky.

 

[Bob F.]

What Film? Ilford recommend not using a pre-soak with their film, citing possible uneven development. However, lots of people do and I don't recall anyone reporting a problem when they did so.

Cheers, Bob.

 

[djkloss]

What Film? Cheers, Bob.

I use PlusX, Efke25, Efke 100 and sometimes TriX - although I don't like the grain with TriX.

I think I read about doing this in Steve Sherman's article on stand-dev.

 

[Bob F.]

In that case, if you are getting the results you want, stick with it. As others have said, the anti-halation layer has done it's job at the time of the exposure so whether it comes out in a pre-wash or during development is of no importance as far as that goes.

Have fun, Bob.

 

[David A. Goldfarb]

With some of the East European films and some developers, I find the presoak does result in more complete removal of the anti-halation layer. I think I first noticed this with Fomapan 200T.

 

[Photo Engineer]

The antihalation layer serves no purpose after the film is exposed.

A presoak is actually helpful to promote even development.

PE

 

[djkloss]

In that case, if you are getting the results you want, stick with it. As others have said, the anti-halation layer has done it's job at the time of the exposure so whether it comes out in a pre-wash or during development is of no importance as far as that goes.

Have fun, Bob.

The whole reason behind my asking this is my determination to get a good negative with Rodinal stand development. Everyone else seems to be able to do it without problems. So I'm trying to eliminate and find the source of my problems. It could even be my scanner as I have not yet printed the negatives yet. I read a post (below is a link) about developing for scanning after I started the post about the anti-halation...I'm seeing a lot of this type of banding and thought it might be from the pre-soak. Now I know it isn't so I need to narrow it down. When I scan the negatives they look grainy with that banding. So maybe its a) the scanner, b) the water bath -incorrect agitation, c) developer agitation, d) me! doh!

I used to get heavy purple stain until I did the longer presoak which I now don't need to worry about and this is going in freaking circles! The banding goes away depending on what dpi I scan at. It's an Epson 1200 Perfection - yeah - old, but it's paid for. hmmmmm....... so...


(there was a url link here which no longer exists)

Donald Qualls states ... "...This depends very much on the scanner, but most if not all will eventually reach a point where you see excessive grain and even banding in the scan, even though the negatives in question still print well...."

I hope these aren't too big, but they show the difference.

Thanks for your patience!

Dorothy

 

[djkloss]

here's another example...the images aren't that great, but they demonstrate what it is I'm having difficulties with.

 

[Bob F.]

Looks like scanner artifacts to me. Not that I am an expert, but I'll bet you sixpence that the bands are running in the same direction as the travel of the scanner head. Print them in the darkroom and I'll bet they are fine.

Cheers, Bob.

 

[djkloss]

Looks like scanner artifacts to me. Not that I am an expert, but I'll bet you sixpence that the bands are running in the same direction as the travel of the scanner head. Print them in the darkroom and I'll bet they are fine.

Cheers, Bob.

I hope you're right. Boy! What an ordeal! But I did learn something.

Thanks
-Dorothy

 

[erikg]

I agree with Bob, that looks very much like scanner noise. I've seen some similar things in scans and I've never seen anything like that from uneven development. Now you know why high end film scanners cost so much! I had a friend who cursed the focus of a lens only to find out after much hassle that the film was buckling in the scanner at the lab. If you can print one with an enlarger that should settle the matter. I too would bet they are fine.

Best, Erik

 

[don sigl]

What Film? Ilford recommend not using a pre-soak with their film, citing possible uneven development. However, lots of people do and I don't recall anyone reporting a problem when they did so.

Cheers, Bob.

I have heard this too. I have heard that Ilford incorporate a wetting agent in their films to help ensure even development..... Maybe, but I always presoak. I have been shooting Ilford films for about 20 years and I have never experienced a single instance (that i can remember anyway) where it was a problem.