EI (exposure index) is a film speed which has been calculated in a way other than the one specified in the ISO standard. Some manufacturers (such as Ilford) use them because they feel that the ISO standard does not reflect the way in which the film will be developed in the real world. Many photographers also use a personal EI to account for the way in which they expose/process/print film, which often differs from the assumptions of the ISO standard.(posted 8860 days ago)With regard to cold, film may be stored at any low temperature desired, so long as it is allowed to warm up to ambient temperature before use (since I live in Alaska, ambient temperature is sometimes - 40 degrees; you have to take film out of the freezer and let it cool down). Many of us store film in the freezer since it lasts much longer.