- Box speed
The term box speed refers to shooting a film with the ISO / ASA rating that is printed on the packaging of the film. For example, Ilford HP5 Plus can achieve good results at various IOS ratings, but the box speed is 400 as printed on the packaging. Deviating from the box speed is refered to as pushing or pulling. Some manufacturers state an ISO range, so that there is not a clearly defined box speed for these films.
Pulling means rating a film at a lower ISO rating than the box speed. The difference to plain overexposing is that during the development, the processing times are adapted depending on the number of stops the film was pulled. Many professional labs offer push and pull processing, but often at a higher cost. Pulling a film generally results in more exposure lattitude, lower contrasts, and less saturated colors.
Pushing means rating a film at a higher ISO rating than the box speed. The difference to plain underexposing is that during the development, the processing times are adapted depending on the number of stops the film was pushed. Many professional labs offer push and pull processing, but often at a higher cost. Pushing a film generally results in higher contrasts, higher color saturations and more pronounced grain.