EI and push/pull development

[kennylovrin]

Hey

Let's say I normally rate an ISO400 film @ EI200. From what I've understood so far that doesn't in itself affect my development time if that is how I normally rate that film.

Does this then mean that if I shoot it at 400, I need to develop it so that I am pushing it to 800?

How are the tone curves affected between these two things? Do I get the same apparent contrast, just different speeds, or will they actually look different tonewise?

The reason I'm asking is that I might know that I get the negatives I want when I run a 400 film at EI200, but sometimes I might want the speed of ISO400, so I need to know if I then (theoretically) should run an ISO800 film at EI400, or rather push the 400 film to 800.

I hope I am making any sense at all. 🙂

Thanks guys!

 

[sevo]

That really depends on whether you merely exploit the high latency of the film to downrate it to get more shadow detail, or whether you are habitually underdeveloping (or developing to a lower contrast) so that you actually downrate it to make up for lost sensitivity.