processing 120 film question

mich8261

mich8261

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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
 
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
 
dilution

dilution

plummerl said:
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
Click to expand...

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

Bob
 
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.
 
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...
 
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
 
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