Kodak TMAX 400 in D-76, Why are times different?

I have several rolls of Kodak TMX 400 to develop. I want use D-76 at 1:1. Looking at the TMAX 400 data sheet I see the time at 70 F is 10.25 mins. Looking at the D-76 data sheet I see the time listed there is 12.5 min.

That's a massive difference. Why do Kodak's data sheets not agree with each other?

What's the proper time to use to develop this film in D-76, 1:1?

Thanks.

Kodak issued a new version of Tmax 400, called TMY-2, several years ago. It was a big improvement over the older version, but needed different developing times.

Confusingly, Kodak never updated the D-76 data sheet for the new film, and they never updated the Tmax Films datasheet, which includes info on Tmax 100, 400, and 3200. Instead, they issued a new Tmax 400 datasheet that covers the new version. The datasheet you want is F4043, and it says you want to develop for 9.5 minutes at 70 degrees in D-76 1+1 for small tank developing with normal inversion agitation. So, now you have a third developing time from Kodak! The F4043 time is correct for TMY-2.

@RattyMouse
whenever I am unsure of development times, I consult the Massive Develepment Chart. See:
http://www.digitaltruth.com/devchart.php?Film=TMax+400&Developer=D-76&mdc=Search&TempUnits=C

You need to use a development time that gives you the desired contrast for the paper on to which you will be printing.

TMY is particularly sensitive to small changes in development conditions, and can be especially difficult to print if overdeveloped because highlight density builds very quickly. So the usual caveat applies even more strongly: don't develop anything important until you've run tests and determined the optimal time for your own setup.

ic-racer said:

You need to use a development time that gives you the desired contrast for the paper on to which you will be printing.

Click to expand...

Seriously? You find this to be helpful to the OP's question?

Here's a curve family I worked up for sheet film TMY2 in D-76 1:1 a few years ago.

I find that my time for 35mm film is close to this, I often develop my TMAX 400 35mm for 13 minutes 30 seconds at 68-degrees F.

I've identified a potential reason for my longer-than-specified development times. I tend to use half the recommended amount of stock. So the recommended times might only be right if you use the recommended 8 ounces of stock solution plus 8 ounces of water per roll (16 ounces of D-76 1:1 per roll of 35mm film).

The curve family tests are valuable but possibly overkill. I recommend a simple process control test to evaluate the contrast you achieve when developing film. Two or three data points would be enough to measure contrast. One simple test is to shoot two or three shots of any convenient target - two stops apart (underexpose, proper exposure, overexpose). You could point the camera at the ground for the purpose. If you can't bear to waste film testing, (or if you get near the end of the roll before remembering you want to test) you could simply take a single bracket shot of your last shot on the roll - two stops overexposed. I personally feel that a contrast index of 0.5 to 0.6 is a good place to aim.

http://beefalobill.com/imgs/Sept9TMY2.pdf