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Rate development at ISO50 or ISO16 ?


SGIBBONS 11 56 1 United Kingdom
20 Jul 2009 11:03AM
Hi Everyone,

Hope youve had a good weekend !

Just wanted to ask a quick question. I recently went on holiday and used my manual medium format film camera with velvia ISO50 film. I used a polariser also which meant an extra 1.5 stops to allow for this. Instead of just adding the extra time required to my meter reading, a friend of mine suggested i reduce the speed of the film to ISO16 instead. My question is do i now develop the film at ISO50 or ISO16 ? Used to know this but i think im loosing it Smile

Thanks for your help !
Krakman 14 3.6k Scotland
20 Jul 2009 11:11AM
I assume you were using an external camera meter ie. one which didn't take readings through the lens?

If so, just develop as normal ie. no pushing and pulling ie. at 50 ISO.

The idea of the change in ISO is to make you 'overexpose' the film by 1.5 stops - this is cancelled out by the 1.5 stops reduction in exposure caused by the polariser, so it should come out OK.

Of course, if it was an in-camera TLR meter then it would compensate for the polariser automatically, so it' would be a different story.
SGIBBONS 11 56 1 United Kingdom
20 Jul 2009 12:16PM
Thanks Krackman for your reply. Yes it was a handheld spotmeter. Thought it would be at ISO50 but just wanted to double check. Ive gotten so lazy with using TLR with my digital camera of late.

Thanks again

Sam Smile

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