[QUOTE=Marco Buonocore;598102]You often read threads about people pushing film to 25000, or whatever crazed speed, and I always wonder the same thing: How were they metering? Unless I know what they were metering for, I don't buy the claims. We've all seen what happens to shadow detail when you push more than 3 stops; it just disappears. I'm not a big zone system guy, but you show me what zone V looks like at ISO 25000. Pretty garbage, is my bet.
The general rule is the more you push the more shadow details you lose. I shot one roll of TMax at 25000 and developed in Acufine, I used my Sigma SA 9 with both spot and martix metering, no shadow detail, moderate grain, but a printable negative.
I wouldn't call that a general rule so much as I would say thats what you're doing. Destroying shadow detail.
Originally Posted by Paul Howell
The only reason you 'push' film is to increase the contrast so you can make the lack of shadow detail acceptable.
I've never seen a 'push' result in increased shadow detail, of course, it wouldn't because you are simply underexposing and overdeveloping.
You aren't making some magic in your film canister, you're misshandling your film on purpose to achieve a trick of the eye.
That trick being that Zones 3-10 look good enough on their own.
Now, some developers (Diafine+Tri-X) give increased shadow detail, but that doesn't mean you're pushing when you expose at 1250 ISO with that combination, you're just using your proper EI for that combination.
All you do when you push is sacrifice shadow detail for either depth of field or motion stop. The less you can get away with 'pushing' the better. Don't worry about the EI, just know what you can hand hold, and what you need for depth of field, and note how many stops that is from your normal speed, because thats how much black you'll have to fill in, either with overdevelopment or higher filters.
during printing you could also decrease the contrast to get some of the shadow detail back. it's there on the film, the film records everything.
But no...it's not there on the film. To get it there on the film, you need to expose more.
Originally Posted by cotdt
I don't see what's so hard about this?
If proper shadow detail was there on the film, you wouldn't be pushing. You'd just be exposing at your normal EI.
Originally Posted by RoBBo
Robbo has it nailed here. Read his post (#12) over and over until it sinks in, then accept it.
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Pushing film is increasing the developing time. If you increase the developing time from your normal time, you are effectively increasing the film speed. Exposing the film normally and then pushing the development should result in slightly overexposed shadows, blocked highlights and increased contrast.
Overdeveloping film has a relatively small effect on the shadow areas and relatively large effects on the highlights. Exposing the film normally and then pushing the development should result in slightly overexposed shadows, blocked highlights and increased contrast.
So if you simply "expose for the highlights" you might lose shadow detail because you need to meter and process for both shadows and highlights.
Originally Posted by jeroldharter
Increasing development time is increasing contrast, not 'pushing'.
Pushing is the process of trying to get more film speed out of your film by underexposing, and then overdeveloping so that you can hide the lack of shadow detail in some nice rich blacks.
Here's a wonderful example of a pushed negative.
No ammount of further development would have given me shadow detail in this shot.
Overdevelopment on a normally exposed shot may have some effect on increasing shadow density, but that's in no way relivant to pushing film, since you're underexposing to begin with, I mean, that's the whole point.
I suppose this is a matter of semantics.
My understanding has been that "push processing" is done independent of the exposure time of the negative with a resulting increase in film speed, contrast, and highlight density. For example, if you take film to a lab and ask for "push processing" they will do so independent of your exposure of the negative.
If you define "pushing" as underexposure and over-development then so be it. From my perspective of your definition of pushing, pushing is not so much "underexposure" but simply placing the low values lower. In my mind, "underexposure" implies inadequately low exposure rather than the purposeful placement of low tones.
I think "a purposeful placement of low tones" is probably the best way to describe pushing film to someone that doesn't want to get swamped with our geek-talk.
I use the term "underexposure" to describe anything less than ideal shadow detail.
I was just confused as to how your original post would help the OP with their question, since it didn't relate to film speed at all and that's what they were asking about, sorry if I came off...well...how I think I may have come off.
No problem. Sometimes I learn a lot ironing out the language as much as anything.