Fixer depletion with MF film?

[kaiyen]

Quick question - my bottle of fixer says that it's good for 35 rolls

of 35mm film. Do I need to adjust that for MF film? Like...would

it be good for half as many MF rolls? (120 film)

 

thanks.

[pascal_miele]

the surface of 120 film is like 135 36, no problem !

[roger_hicks1]

Dear Allan,

 

Roughly (but well within experimental error) a roll of 35mm film, a roll of 120 and a sheet of 8x10 inch film have the same surface area. They're certainly close enough when it comes to figuring fixer exhaustion.

 

Cheers,

 

Roger

[roger_hicks1]

It's just occurred to me that some people may not know the old rule of thumb for fixing times and fixer exhaustion.

 

Put a drop of freshly mixed fixer on a scrap of unprocessed film -- the leader off 35mm is ideal. Let it act 20 seconds. Chuck the scrap into the bulk of the fixer and start the timer. When you can't see the spot any more, that's the clearing time. Fix for a minimum of twice the clearing time and a maximum of three times.

 

Repeat the test each time you use the fixer. When the clearing time has doubled, replace the fixer.

 

What exhausts most modern fixers is silver build-up, so the above is only an indirect test, but it's surprisingly reliable.

[kaiyen]

Ah - so the decreased length of the 120 film gives it roughly the same surface area as a 35 mm roll. cool.

 

I hadn't heard of that test method before (I was just going to get some of the fixer test drops after I got somewhat closer to 35 rolls processed...I'm at a whopping 7 right now).

 

thanks.