22nd March 2008, 01:02 AM
Re: How to check of a roll of film is still good
There are both negative as well as positive 'pro' and 'consumer' graded emulsions.
Generally, positive film is always a little more sensitive to heat and humidity as compared to negative material, regardless of whether they are graded 'pro' or 'consumer'.
However, for 'pro' graded stocks, manufacturers usually batch test and select the film at it's targetted optimal age and keep it within fairly controlled shipping and transportation conditions. They also demand that a retailer selling pro graded emulsions store such material under controlled refrigerated conditions. The result? A user gets the 'pro' film, kept at it's optimal storage conditions at it's performance peak age, with as little deviation from batch to batch as possible (or so most hope).
If truth be told, some of the 'pro' graded stock is the same exact material as consumer stock, except the way they are tested, selected, handled and shipped to reach professional users withing an optimal time frame, and of course, they always have to be kept under optimal conditions. Note: Not all emulsions can be segregated so easily, as some technical films will always have be treated and handled as 'pro' stock because they cannot be shipped or stored under typical consumer film conditions.
It gets really fun when you work with raditation ready, technical and litho emulsions!
Just to add, when I had to research technical materials, the best place to contact was the Eastman/Kodak Professional Division as they have all the technical papers and specs for optimal film age, usage, storage prior to exposure as well as post developed film archival storage.
IIRC, in an article in Modern or Popular (?) Photography (Petersen Publishing) in the early to mid 80s, they had an article about how a museum kept it's processed slides for archival purposes. It involved specially lined/padded Kodak storage silver foil bags and deep freezing (somewhere on the minus scale), under very strictly controlled conditions. IIRC hor!
Last edited by Dream Merchant; 22nd March 2008 at 01:20 AM.