Quote Originally Posted by MattKing View Post
For clarity, "pushing" and "pulling" refer only to modifications of your development time. The reason that one decides to modify the development time is that one wants to modify the contrast of the film.

A "push" development increases the contrast. It also tends to push the area of the curve near the toe up into the straight part of the curve. By doing this, we make flat subjects appear more contrasty. We also improve slightly the appearance of the shadows and near shadows in films that have been underexposed. A "push" development is often used when we are forced to underexpose film (i.e. meter using a higher than box speed EI). For negative film, a "push" development gives little or no improvement to the underexposed shadows. It may help though with shadows on transparency film.

A "pull" development decreases the contrast. It also tends to push the area of the curve near the shoulder down into the straight part of the curve. By doing this, we make contrasty subjects appear less contrasty. We also improve slightly the appearance of the highlights and near highlights in films that have been overexposed. A "pull" development is often used when we are forced to overexpose film (i.e. meter using a lower than box speed EI). Most negative film has a lot of latitude for over-exposure, but even so a "pull" development may make it easier to print over-exposed highlights. For transparency film, a "pull" development may be very helpful with overexposed highlights.

C41 negative films tend to decrease graininess when you overexpose them. Other films tend to increase their graininess when you depart from the recommended development.
But what happens if:

1) Expose at 100, develop at 200.
2) Expose at 100, develop at 50.

vs.

3) box speed 100, expose at 200, develop at 200.
4) box speed 100, expose at 50, develop at 50

Makes sense?
As far as I now, when you over-expose or under-expose, you also correct the development time.

This is relevant because some manufacturers plot different density curves, keeping E.I. constant, according to development time. The difference you get is a steeper curve as development time increases. For instance check this link, but there are many others available online.
http://www.maco-photo.de/files/image...t_pan80_en.pdf

For instance, check the curve "Gevatone 66, G 74 c, 30 C."
It seems you can get about 1 stops of extra speed (log exp from -1.8 to -2.4) when you increase development time from 20 to 70 seconds. This comes at the expense of increased contrast - the gradient of the curve gives you the Gama contrast. In this developer and temp combo, it goes roughly from 0.75 to 1.9 at the shadows to mid-tones for the longer development times.

This tells me it is not the same to "+1 push" to 200 and develop at 200 or expose at 100 and develop as 200.

As far as I can recall, and I might need to check again, Ansel Adams N+1 meant expose at N and develop as N+1. Right?

There should be as many options as in the table below. Anyone care to comment?

Expose/Develop N-1 N N+1
N-1 Published ? ?
N Adams contraction Ok Adams expansion
N+1 ? ? Published