I'm very new at this home developing lark and I chose Diafine for it's ease of use. I've only processed three films so far, each one different. A roll of Acros @ 160, one HP5 @400 and the last one a roll of Tri-X @ 640. The Tri-X was shot on a very sunny day with pretty much all shots being at f16 but the results were good.
Take a look at my shots here
http://www.flickr.com/photos/kuvvy/tags/trix640/
Yes, they would be different. They are different films. Diafine does not treat all films exactly the same way, but it develops each to exhaustion.
With Kodak Tri-X, Diafine typically produces an effective speed (EI) of 1000 to 1250 (listed as 1600 on the box, but I have always disagreed with that). The difference between Tri-X rated at EI 640 and 1250 is one stop. Quite acceptable, and I'd expect you to get good results.
I do not know what effective speeds one would get with Acros or HP5, but I presume the box said something about it, didn't it? I no longer have mine, as I only process Tri-X in Diafine.
Understand this. When you place an exposed film in a tank with developer, typically it begins to process silver halide that has been exposed to light. How fast it does this depends upon temperature, dilution, and other variables. If you take the film out 'early' or 'late' according to processing times listed for that particular film and dilution and temperature, you are said to be 'pulling' or 'pushing' the film. This is quite acceptable, and is a well-known, well-understood, and often-used means of controlling your final product, the negative.
Diafine, and indeed all two-part developers, were made differently. They consist of the same basic components; one or more developing agents, a restrainer, an accelerant, and a buffer. The first solution contains at the very least a developing agent. This is designed to soak into the film's emulsion like a sponge. And like a sponge, once it is saturated, it is saturated. More or less time (or temperature) is not going to make it soak up more developer. Does this make sense so far?
Now, when you pour the first solution back into your jug, the developer that has absorbed into the film's emulsion remains there. Does it begin to process the film? Yes, a little. But the developing action is quite slow - it needs an accelerant to really get cracking. And that is what is in the second solution.
When the second solution hits the film, it finds the first developer lurking in the film's emulsion, combines with it, and begins chomping down light-exposed silver halide like a hungry fat boy at a free hot dog stand. However, it needs two things for this to continue to happen. One, it needs solution A developer to be present, and second, it needs light-exposed silver halide to operate upon.
Now, if you leave typical one-part developer in your tank for a very long time, it will eventually convert all the silver halide to metallic silver and you will end up with a nice blank film strip, having poured all the silver down the drain with your fixer. And Diafine would do that too - if it had an unlimited supply of solution A. But it doesn't - it only has what is absorbed into the film's emulsion. When that is gone, it stops developing action.
We call that 'developing to exhaustion.' It's a good thing, because you cannot overdevelop your film. It's a bad thing because overdevelopment is another word for 'pushing' film. You can't 'push' film in two-part developers like Diafine. It is a good thing because when you shoot 'available light', you typically are taking photos of high-contrast scenes - and Diafine has the effect of lowering contrast. In a high-contrast scene, that can be good.
Diafine is a good developer, and being panthermic and time-insensitive, it is an 'easy to use' developer as you said.
However, it is not an 'all-purpose' developer. It seems to 'like' some film quite a bit more than others. It gives a different effective speed to different films, and unless you have some idea of what speed your film should be exposed at for Diafine, you might be at risk of crappy exposures. It almost always gives a film speed increase, so shooting in very bright light might be bothersome - unless you fancy using very fast shutter speeds, stopping down like a mad thing, or using neutral density filtration on your lens. It also does not - I repeat, does not - allow for pushing or pulling film speeds. It is what it is.
The term is TANSTAAFL - There Aint No Such Thing As A Free Lunch. Diafine is very good at what it is good at - available light, lowering contrast, easy to use, time and temperature insensitive. But it is not the be-all developer, and it cannot be effectively tweaked to make it behave differently that I am aware of.
Youtube videos to the contrary.
