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Rating and Timing film?


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#1 Michael Dean Gibbs

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Posted 28 June 2007 - 01:15 PM

Good Afternoon,

There are a few questions that I have, that I have been unable to get my mind around.

First, when a DP says that he rates, say 52/7218 500T film at a 320asa, does this mean that contrary to Kodak's specifications, the DP finds "normal" exposure to be 2/3 over? Or is this shorthand meaning that the DP will overexpose by 2/3 of a stop but plans on pulling an equal amount?

Secondly, I am in the process of running exposure tests on some different stocks to better familiarize myself with their uniqeness. I will make two prints...a "one-light" to inform me about latitude and a "timed" print. My question is...what is it that the DP is trying to discover with this "timed" print?

Thanks for your time,

mdg
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#2 David Mullen ASC

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Posted 28 June 2007 - 06:52 PM

First, when a DP says that he rates, say 52/7218 500T film at a 320asa, does this mean that contrary to Kodak's specifications, the DP finds "normal" exposure to be 2/3 over? Or is this shorthand meaning that the DP will overexpose by 2/3 of a stop but plans on pulling an equal amount?

Secondly, I am in the process of running exposure tests on some different stocks to better familiarize myself with their uniqeness. I will make two prints...a "one-light" to inform me about latitude and a "timed" print. My question is...what is it that the DP is trying to discover with this "timed" print?


Usually rating a 500 ASA stock at 320 ASA means that the DP will ask the lab to process normal, ending up with a developed negative that is slightly denser than normal. The brightness will be brought down to normal in the telecine transfer or in print timing.

Usually when a DP overexposes and pull-processes, he does it by at least a one-stop amount. The looks is different than printing down a dense negative. If you overexpose by one stop and pull-process by one stop, your negative density should be normal. But the contrast will be lower and the colors a little softer. Overexposing, processing normal, and printing down to normal later tends to make the blacks blacker and thus the colors a little richer, within reason (too much overexposure and you push too much detail into the flatter shoulder of the stock.)

You make a one-light when you don't want the lab to correct for your over and underexposures, so you can see when the stock goes white or black, and you make a timed print to see what over and underexposed footage looks corrected back to normal.
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#3 Michael Dean Gibbs

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Posted 29 June 2007 - 12:36 AM

Thank you for the response David.

What I would like to do in the next couple of months is to create data bank of still images. I would like to be able to go to my computer and click on the file that says 52/7218 or 52/7229 and be able to compare and contrast '18 stock overexposed 1-stop to '29 stock overexposed 1-stop. If this were a project that you were to take on...what would be the process by which you would go through in post?

Negative - telecine - computer - grab?

Negative - print - telecine - grab?

Or another way that I am unfamiliar with?


I really appreciate what you do for people like me!

mdg
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#4 David Mullen ASC

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Posted 29 June 2007 - 01:37 AM

Negative - telecine - computer - grab?

Negative - print - telecine - grab?


Projection prints aren't really used for telecine work, so I'm not sure what the point would be except to compare two different prints and not worry about the high contrast.
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#5 Dominic Case

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Posted 29 June 2007 - 02:19 AM

Assuming you do as David suggests, which is transfer images from the original neg via telecine, then digitise them, the question to ask is how much will you have the images corrected in telecine?

When you over or underexpose the negative, there are changes in the negative density (which are easily corrected, up to a point, when you print) and slight changes in either shadow or highlight contrast (depending if you expose up or down). These shifts can't be corrected in printing, but can still be dealt with in telecine.

If you want to compare the results of printing various stocks and various exposures, then you should ideally have the telecine transfers done with minimal telecine grading. Even so, the images on your monitor won't really give you the same results as looking at a projected print.

If you want to compare all those results in a video finish, then it would make sense to correct them for all you are worth at the transfer stage: which means there won't be much difference left to look at in your computer files - especially with just single-stop changes in exposure.
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#6 Michael Dean Gibbs

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Posted 30 June 2007 - 12:25 AM

Thanks for the insights gentlemen!

It sounds like the best way for me to compare and contrast different stocks, then, would be to compare prints and not digital transfers...is this correct? And is this because so much of the information will have been lost through the analog-digital transfer?

Obsiously, I'm still very much in the learning process. The best way for me to learn how different stocks vary, would be to shoot, shoot, shoot. But, unfortunately, I don't have any projects presently to work on...so as I look for work I'm trying to fill my time with useful exercises, so that I can become better informed.


mdg
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