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How mush should I push or pull?


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#1 Hugo Alexandre

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Posted 12 February 2008 - 08:19 PM

Hello. I shot 100ft of 7231 (80D ASA) film thinking it was 7222 (250D ASA). If I want to get good exposure when I develop it, how much should I push or pull? And what are the pros/cons in terms of grain, etc..

Thanks.
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#2 Bryant Jansen

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Posted 12 February 2008 - 08:59 PM

Hello. I shot 100ft of 7231 (80D ASA) film thinking it was 7222 (250D ASA). If I want to get good exposure when I develop it, how much should I push or pull? And what are the pros/cons in terms of grain, etc..

Thanks.


Hugo,

Exposing an 80 asa rated stock at 250 asa is underexposing the stock by 1 2/3s stop, so to reach the recommended asa of the film you would need to push the film that same amount: roughly two stops. I'm not exactly sure how the stock will react because i have not pushed 7231, but the general effects are an "increase in contrast, graininess, and fog level" (that's a quote directly from the ASC Manual). I have pushed 7212 (100T) one stop and was quite happy with the results. Pushing a stock by two stops will definitely increase these effects, but it will still be acceptable. I wouldn't go any more than two stops though.

Hope that helps,

Bryant Jansen
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#3 Dominic Case

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Posted 12 February 2008 - 10:53 PM

Black and white stocks definitely show an increase in contrast when you push process. (Colour neg is more stable in contrast). I always recommend under-compensating, so as to minimise the side-effects such as contrast and grain build-up. So in this case I would think you should get the neg pushed one stop. It will end up a little thinner than a correctly exposed neg, but much of that can be allowed for in your print or telecine transfer.

Since you've asked the question, I wonder if you know the relationship between exposure and EI rating. Quite simply, each stop is double or half the exposure, and therefore each double or half of the EI rating is equivalnet to a shift of one stop.

80 to 160 would be one stop: 80 to 320 would be two stops. So 80 to 250 is in between those.

The series of EI ratings, in one-third stop intervals, is

25; 32; 40; 50; 64; 80; 100; 125; 160; 200; 250; 320; 400; 500; 640; 800; 1000 etc.
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#4 Hugo Alexandre

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Posted 12 February 2008 - 11:17 PM

Black and white stocks definitely show an increase in contrast when you push process. (Colour neg is more stable in contrast). I always recommend under-compensating, so as to minimise the side-effects such as contrast and grain build-up. So in this case I would think you should get the neg pushed one stop. It will end up a little thinner than a correctly exposed neg, but much of that can be allowed for in your print or telecine transfer.


Thank you for the suggestion. However, this is for a class assignment and there is no digital post-production work allowed. So if I want it to look acceptable when projected, would you still recommend to push 2 stops?
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#5 David Mullen ASC

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Posted 12 February 2008 - 11:30 PM

Thank you for the suggestion. However, this is for a class assignment and there is no digital post-production work allowed. So if I want it to look acceptable when projected, would you still recommend to push 2 stops?


I would push one-stop; the remaining bit of underexposure compensation just involves printing it "up" to a normal brightness. It will just print at a lower number than if the negative were at full density.

It's not like one method looks "acceptable" and another method doesn't. You have artifacts no matter which technique you pick, hence why the safest thing is to compensate partly by pushing and the rest in printing.
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#6 Hugo Alexandre

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Posted 12 February 2008 - 11:43 PM

I would push one-stop; the remaining bit of underexposure compensation just involves printing it "up" to a normal brightness. It will just print at a lower number than if the negative were at full density.

It's not like one method looks "acceptable" and another method doesn't. You have artifacts no matter which technique you pick, hence why the safest thing is to compensate partly by pushing and the rest in printing.



Hey. Thanks for your reply. But there's something I don't understand though. This business about "printing 'up' to a normal brightness". Is this something special that I should tell the lab about, apart from pushing the neg 1 stop?
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#7 David Mullen ASC

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Posted 13 February 2008 - 12:31 AM

Hey. Thanks for your reply. But there's something I don't understand though. This business about "printing 'up' to a normal brightness". Is this something special that I should tell the lab about, apart from pushing the neg 1 stop?


Did you shoot a "normal" grey scale reference at the head of the roll? If so, just tell them to print for the grey scale at one light. If not, tell them to do a "best light" or "timed" print. Or just be honest and say that the roll was accidentally underexposed and to please print to look normal in brightness.

Remember, "push one stop" is an instruction for processing the negative. "Print for grey scale", "print to look normal brightness", whatever you tell them, doesn't affect the negative, it's an instruction regarding the print off of the negative.
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