processing 120 film question

[mich8261]

as I have stated in a few other posts, I am new to the analog darkroom. I am currently taken a B&W class which is where I learned to develop my own film. So far I have processed Tri-X 400 135/36 film. I think I might be slightly overdeveloping, but that is for another thread. My question is about processing my first roll of 120 film (also Tri-X). I noticed when I opened the box that the Kodak suggested time for D-76 is shorter than for 35mm film. I thought that the surface area of 120 film was the same as 135/36. Am I missing something?

Thanks

 

[plummerl]

First, the surface area does not really drive the dev. time. It only applies as a depletion factor. Second, are you sure the dilution factors are the same for both? This is usually the reason for differing dev. times. I would recommend that you take a look (if you haven't already) at the Massive Dev Chart: http://www.digitaltruth.com/devchart.html

 

[rogue_designer]

also, aren't there two TriX formulations? That could be a factor.

 

[mich8261]

dilution

dilution

First, the surface area does not really drive the dev. time. It only applies as a depletion factor. Second, are you sure the dilution factors are the same for both? This is usually the reason for differing dev. times. I would recommend that you take a look (if you haven't already) at the Massive Dev Chart: http://www.digitaltruth.com/devchart.html

I'll check when I get home, but I think Larry has a point. I am still new to this and subtle differences trip me up. I have looked at the Massive Dev chart. The agitation method seems different than what my instructor is suggesting so I am not sure I want to mix the two (his agitation and their time). Perhaps when I have the whole thing down I'll be more adventurous!

Cheers.

 

[plummerl]

I have usually found the MDC to be my friend! I do 35, 120 and 4x5.

 

[shg005]

in average D-76 is "almost safe developer", if you will use it as 1:1 or 1:2 you have to make a big mistake for the overdeveloping.

 

[40oz]

use this for Tri-X development times:
http://www.kodak.com/global/en/prof...f4017/f4017.jhtml?id=0.2.22.14.19.16.14&lc=en

There are two kinds of Tri-X: 400TX and 320TX. Developing times for 400TX is slightly shorter than for 320TX, which could be the discrepancy you are noticing - not everyone differentiates which Tri-X they are using. Kodak makes no indication that 120 film should be developed any differently than 35mm.

 

[mich8261]

As I thought, I hadn't RTFM!!! I was looking at the undiluted times.

 

[FrankS]

Just remember to use 500ml of developer instead of the 300ml that 35mm film takes. Sounds like a stupid reminder, right? Only an idiot would forget right?

guilty!

 

[rpsawin]

You are probably processing TXP 320 Tri-X Pro....not the same film as 35 mm Tri-X 400.

Bob

 

[Pherdinand]

The MDC is no bible.
I have a very limited developing experience, but i already noticed, that the MDC suggests as delta3200 in 120 format to be used at ei 1250 if developed in studional (aka rodinal special).
I did that on some frames, and used it as 3200 speed film ont other frames,same roll.
The 1250 ones are overexposed visibly.

I guess too many factors play a role (like agitation) and the MDC is just a starting point.

 

[mich8261]

FrankS,

I am not sure I know what you are referring to. I use Samigon tanks which require 20-24 oz (roughly 600-700 ml). I wouldn't use any less because it would leave a portion of the film out of the developer (except during the brief agitation). Maybe that's what you were referring to. If I only had one roll of 35 I could cut the amount in half...

 

[kaiyen]

Michel,
I think that's exactly what Frank meant - if you're used to using only 10-12 oz for 35mm and do a lot of single rolls in 2 roll tanks, you might forget that you need 20-24 oz for a single 120 roll.

I always use 20 oz regardless, FWIW.

allan

 

[rpsawin]

I have returned from the Oracle....

http://www.kodak.com/global/en/prof...f4017/f4017.jhtml?id=0.2.24.14.19.16.14&lc=en

Check out the pdf.

Bob