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grain pushing


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#1 shameline

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Posted 26 August 2007 - 03:02 PM

Hi,
I'll be shooting a short on 16mm (my first time shooting 16mm, very exciting :lol: , very probably on 7218, unless you have any suggestion for another film stock, shooting tungsten), and I want to push the grain to get a little material/organic feel on the picture.

I went through different posts on the forum, but I'm still not sure of the overall process.

The main technique, as I understood, would be to push the film. <_<

Let's say I want to push the film of 1 stop. If I have a reading on my light meter of 5.6, should I set the lens to 4? And ask the lab to push the film of 1 stop on the during the processing? I'm not exactly sure what is the formal way to ask them...

If I want to push it half a stop, how am I sure my f stop is going to be an accurate half a stop of 5.6 (or it doesnt really matter because the film latitude? ):huh:

(I understand the best way to know is to do test though)...
If anybody has a step by step approach, that would be very valuable.

Thanks for your advices.

Seb.
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#2 Nick Mulder

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Posted 26 August 2007 - 04:03 PM

Let's say I want to push the film of 1 stop. If I have a reading on my light meter of 5.6, should I set the lens to 4? And ask the lab to push the film of 1 stop on the during the processing? I'm not exactly sure what is the formal way to ask them...

No.

pushing the film at the lab involves leaving it in the developer for longer - so opening up a stop and developing it for longer you are going to a. overexpose one stop and then over-develop one stop - i.e. 2 stops more density ... Some might do this for various reasons but it is not the essence of a push.

A push is the opposite at the camera end - we underexpose the neg and then over-develop in processing so the net gain in density is 0 (there are more factors at play with regards to the final look such as grain as you have mentioned but that is the general logic). If you are reading 5.6 you'd actually close to 8.

To make things simple in your light meter simply adjust the ASA of your film - so for 7218 set your meter to 1000 then all readings will be correct for the push.

Oh, and yes >> its as simple as asking for it 'to be pushed one stop' - you wont get any odd looks saying it like that :lol: Sometimes in stills photography its as simple as writing '+1' ... but you want to be sure you dont get your wires crossed so there's no harm in spelling it out fully .

Edited by Nick Mulder, 26 August 2007 - 04:06 PM.

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#3 shameline

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Posted 26 August 2007 - 06:10 PM

Thank you for the explanation :rolleyes: .

How do I know accurately that when setting my light meter to 1000, I'm actually underexposing just 1 stop right on the dot? (just taking the mesure with one asa, the other and compare?)

If I want to push only half a stop, should I rate the asa to 640? Is there any kind of chart (if I can say so) That would show the relation/rule of thumb between asa/ f-stop change? :ph34r:


By curiosity, what happens if I do the contrary (overexpose 1 stop, pushing the film? )


Thanks again. :P

Seb.
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#4 Dominic Case

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Posted 26 August 2007 - 08:30 PM

Is there any kind of chart (if I can say so) That would show the relation/rule of thumb between asa/ f-stop change?

Every change of one stop is double (or half) in ASA rating.

So if you have a reading at ASA 500, then setting the ,meter to ASA 1000 will give you exactly one stop underexposure. When the lab pushes one stop, it will bring the density of the neg back to (more or less) normal. Because the contrast is changed when the process is changed, it's an imprecise science.

640 is only a third of a stop away from 500. But that's only 1/th of a stop different from half a stop away (about one printer point) so it's not enough to worry about.

The scale - in 1/3 stop intervals - goes

20, 25, 32, 40, 50, 64, 80, 100, 125, 160, 200, 250, 320, 400, 500, 640, 800, 1000, 1250, 1600, 2000

You'll notice every 3 steps, the number is doubled. There are approximations (twice 64 isn't really 125) to keep the numbers easy, they don't realy have any measurable effect.
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#5 shameline

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Posted 29 August 2007 - 01:26 AM

Thanks for all those accurate information.
I was wondering if there were other technique to push the grain. Would it be possible to shoot 400asa, expose for 400, and have it processed at 500? or any alternative... :blink:


Thanks again! :rolleyes:

Seb.
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