Tri-X (TX400) 35mm vs. 120 - Are the emulsions identical?

[stormbytes]

Running some tests on TX-400 and seeing as I shoot both 35mm & 120 I'm trying to decide if I need to test each of the film formats or if testing a single format would suffice.

Your thoughts? Experiences?

[MattKing]

Good question.

You might find some useful information in the following thread:

http://www.apug.org/forums/forum37/2...5mm-120-a.html

Matt

[Photo Engineer]

They are identical.

If the same film is coated on the same type of support of the same thickness then they are identical. If it is coated on different supports or of a different thickness, then there is a tiny modification in the coating formula sometimes to allow for coating differences.

PE

[fschifano]

So that explains the differences one sees in processing times between two formats of the same emulsion. Thank you.

[Photo Engineer]

I've explained elsewhere the effects of macro and micro contrast vs edge effects. These are often adjusted by different development times for different formats of otherwise identical films.

This is done to give the optimum results for a given format regarding contrast and image structure.

So, that also enters into the film handling equation.

PE

[stormbytes]

When all said and done, does this mean that results from film tests carried out on TX400/35mm can be expected from the same film in 120 format (processed the same way)?

[ann]

don't forget the differences that may occur with equipment. it can have an effect on one's personal EI.

[Photo Engineer]

When all said and done, does this mean that results from film tests carried out on TX400/35mm can be expected from the same film in 120 format (processed the same way)?

Dan;

I've explained the difference between micro and macro contrast elsewhere on APUG. I don't want to go into it again, but basically, two formats may have identical curve shapes on the macro scale, but the micro images differ in order to adjust sharpness factors and contrast when enlarged.

PE