question about developing

[llung]

A question about developing from an amateur who knows absolutely nothing about darkroom work.

Sometimes I'm in the middle of a roll and decide that I would rather have higher speed film in my camera. I don't do any of my own processing - I simply drop the film off and if I pushed the film then I tell them that I did so. Now say I have a roll of Delta 400 in my camera and shoot exposures 1-18 at 400 iso. Then I find myself engulfed in total darkness and decide to push the film a stop for exposures 19-36. Obviously, if I just get it developed half of the prints will be either over or under exposed depending on whether I instruct the shop to develop at 400 or 800. No problem. But if I later decide to get enlargements for, say exposures 8 and 30, is there any problem with just telling them to expose 8 at 400 and to push 30 by one stop.

Put another way, and hopefully in much simpler terms, when the negatives are being "rinsed" does it matter whether you've pushed the film. Is over/underexposure - as in pushing and pulling - merely something that matters for the purposes of printmaking and has absolutely no effect on how you treat the negatives?

As I said, I know absolutely nothing about film processing, so any help would be greatly appreciated.

cheers,
Lucas.

[filipdabrowski]

I've always thought you push film when processing and NOT in camera. Guess I was wrong. Sorry, don't know how to answer your question, but the pushing of film does have me intrigued.

[knighty]

You can't push half a film - its either all of it or none of it. The way it is done is by adding extra development time, from memory its 25% extra per stop. So if I have a roll of Tmax 400 that I would normally develop in D76 for 16 minutes and I shot that roll at 1600iso (2 stops underexposure) I would need to add 2 stops development. So it's 16 minutes + 25% (20 minutes) + 25% of 20 minutes so it would be in the developer for 25 minutes.
You said about getting prints done at a later stage and whether you can get them pushed. No can do, as I explained above its done in the film development stage. By the time your film has been fixed it is too late. Sure, there are ways to get a print out of an underexposed neg but quality will suffer enormously...

[llung]

Knighty: I actually got a conflicting opinion today and now I'm really confused. Somebody else told me that pushing/pulling is merely a matter for printmaking; you're telling me that the negatives are essentially 'fixed' according to how they are processed. In any event, I do know that it's possible to over/underexpose when making prints, so I guess the question is what happens to the negatives when you have them processed. I would think that either way you could still get away with pushing only half a roll.

Let's assume for a moment that you're right - that the negatives are essentially 'fixed' at the point of processing. I truck down to the shop wth my half pushed roll of Tri-X and tell them that I pushed the film by one stop, so they basically 'fix' the negatives at 800 iso. I get a contact sheet back where half the shots are overexposed. Now I go back and ask them to underexpose a few of the shots during the printmaking process by one stop. I would think that the prints should come back properly exposed.

Now let's take the other opinion I got today. I go down to the shop with the same roll. I tell them that I pushed the film by one stop and nothing happens when they're processing the negatives, but they overexpose by one stop. Half the prints have been overexposed, but nothing has happened to the negatives. So I head down there and ask them to make some enlargements for me from the part of the film that I shot at 400 - basically I don't tell them anything. I suspect the enlargements would be properly overexposed.

So the question is, does it really matter who is right about the negatives so long as you can over/underexpose during the print-making process?

Thanks for your patience. I'm still learning...

Lucas.

[knighty]

Lucas,
The ISO that you shot the film at has no relevance to the printmaking process. You could tell the lab you shot your film at 3200 when you really shot it at 100 and it would make no difference in the print at all. You can't put detail into a print where there is no detail in the negative.

[vid64]

Hmmm there's some confussion here. When you 'push' a film, you are essentially underexposing. If developed normally, you'd end up with 'thin' negs, ie, the negs would look pale and so print dark. While this can be compensated for during printing, it's far from ideal.

When a 'pushed' film is developed, the development time can extended to compensate for the underexposure, and produce negs that print better than if they were developed normally. However, it's still a compromise and the result can be more grainy and contrasty than you might like. Some people like this effect and do it deliberately!

In a situation where half of the film is pushed (underexposed) I'd recommend extending the development time (push processing) to compensate as neg film tolerates overexposure better than underexposure. The negs from the half that was exposed normally, will look over exposed (ie too dark on the neg) but with compensation at the print stage they will print better than the underexposed negs would if the film was developed normally.

The best solution is to use the right film for the job!