Niall,
why do we push and pull films? Well, first of all the ISO rates do not have to be accurate for your equipment and taste. Therefore many people do calibrate their processes to achieve the desired result. Besides that you usually push films when the contrast of scene is low. By pushing you extend the density range on the negative for a given exposure. Let's say the contrast of scene is 3 EV steps then you increase the ISO setting (underexpose) and prolong the development so that the negative density range will be 1.2 (Dmax - Dmin) which equals 4 EV steps. Pulling would be exactly opposite.
Pushing provokes grain, pulling is a very common way of adjusting to standard needs and still be safe on bright scenes. It is usually better to development shorter and print harder instead of doing the opposite.
br
Michael
why do we push and pull films? Well, first of all the ISO rates do not have to be accurate for your equipment and taste. Therefore many people do calibrate their processes to achieve the desired result. Besides that you usually push films when the contrast of scene is low. By pushing you extend the density range on the negative for a given exposure. Let's say the contrast of scene is 3 EV steps then you increase the ISO setting (underexpose) and prolong the development so that the negative density range will be 1.2 (Dmax - Dmin) which equals 4 EV steps. Pulling would be exactly opposite.
Pushing provokes grain, pulling is a very common way of adjusting to standard needs and still be safe on bright scenes. It is usually better to development shorter and print harder instead of doing the opposite.
br
Michael
