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01-08-2009, 06:42 PM   #1
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black and white film exposure question

for b&w film, is it better to overexpose a bit like C-41?
what happens if i shoot a few frames iso200 or iso 800 w/ TX400 and leave it to my lab to process at iso 400? will they be able to "correct" it like C-41?

01-08-2009, 07:55 PM   #2
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I tend to "overexpose" B&W film by several stops. What you describe is not a good way to get quality pictures.
01-08-2009, 08:05 PM   #3
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I'd try to shoot at the rated speed with Tri-X, ...that's generally what I do, but I process my own. Black and white film has pretty good latitude, but I wouldn't rate Tri-X at 800 unless I intended to push, in general, especially if someone else were doing the processing. You can under-rate it, but usually that doesn't give you any blanket benefit, I'd rather know when giving it a little more is what I want to do for a particular frame.

Most folks starting out wouldn't be hurt by giving it a half a stop extra, if in doubt, but, no, there's no blanket recommendation i'd make such as with c-41, which usually can always use a thrd of a stop or so.

Certainly, though, a machine printer can save a neg that's a stop or so off: there's generally enough latitude there. I don't mind saying if it were my lab, I probably could do somewhat better for you. At least a me in practice.

Anyway, with black and white, there's much more margin for error than with, say slides, or blowing out your highlights in digital (I treat digital much like slide film) but there's little benefit, generally, to running at far off the rated speed unless you really just have to to get the shots. And there I'd advise push-processing.
01-08-2009, 08:07 PM   #4
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For B&W film you expose for the shadows, i.e. make shure that you get some shadow detail. So, yes, overexposing a bit is better than underexposing.

01-08-2009, 08:58 PM   #5
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Good information there ... thanks you ... I'll take that on-board before venturing out with B&W loaded in the Spottie.
01-09-2009, 01:02 AM   #6
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Check the other thread about BW film

If you are going to send the film out for processing you need to match your speed to the lab development cycle.
Labs run cycles of say 6, 10, and 15 minutes but no in-betweens

So decide on 1 or 2 films and then meter the light in an averag scene (with whites and blacks)
To do that select an "average scene" (one with whites, blacks and all the in-betweens) and then meter the light for box speed.
Expose -2,-1,0,+1,+2 stops from what the metering said, then a blank and then another scene in the same way.
After you send the film you will receive the scans/prints. Check for shadow detail and for whites that are not "bloomed" and select the best of the exposures. It maybe an inbetween as well, even though it is genrally safer to overexpose by 1/2 stops.
In that way the next time you load this film you will set the ISO accordingly. If it was 400 then -2=100, -1=200 [-1/2=320], 0=400, [+1/2=500], +1=800, +2=1600
01-09-2009, 07:35 PM   #7
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thanks for the tips! i'll keep them in mind, gotta finish up my roll of TX!
01-09-2009, 07:46 PM   #8
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With Tri-X I tend to overexpose slightly and underdevelop (pull). So I rate it at ISO 200 or 250. Offers detail preservation/grain reduction in shadows and works with particularly contrasty scenes.


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