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A Question about film rating


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#1 Mackay Valentine

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Posted 10 March 2007 - 12:49 AM

hi all,
I'm a cinematography student about to shoot a short 16mm film with Kodak 5218. Originally I had planned to shoot the short with 5217, but unfortuanltey I wasn't able to get it in time. Now I have no choice but to shoot with the 5218, which I'm afraid will be too grainy.

I've heard that film stocks can be rated at different ISOs, though I'm not sure how to go about doing this, or what the results will be. I'd love to get a sharper image with the 5218, and any advice on how to achive this would be much appreciated
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#2 Patrick Cooper

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Posted 10 March 2007 - 01:39 AM

Ive had little experience with shooting negative cine film (only used it once recently) but it's a well known and common practise to overexpose it slightly in order to reduce grain. Many cinematographers deliberately overexpose neg film by half a stop or two thirds of a stop to produce finer grained footage. I notice that 5218 is rated at 320asa in daylight with an 85 filter so (when filming outdoors during the day) you could set your light meter to 250asa, or alternatively keep it set at 320asa but always remember to open up the aperture half a stop or two thirds of a stop from the recommended reading. (Easier just to set your light meter to the desired asa rating.) Some negative films have an exceptionally wide exposure latitude and can be rated a whole stop slower and sometimes more but I would do some research on the particular stock before overexposing to that extent. Apparently, some unintentional 'noise' can be introduced into the telecine if the film is overexposed too much. Some sources claim that overexposing neg film can also give an increase in contrast which is a good thing if you are after sharpness. A contrasty image can give the viewer the impression that the image is slightly sharper than it really is. And of course use high quality prime lenses at mid aperture for optimal sharpness. And don't stack too many filters on those lenses!
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#3 Michael Nash

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Posted 10 March 2007 - 02:05 AM

5218 is 35mm; 7218 is the 16mm version.

Overexposing a negative stock increases the density of the image, which in turn gives you a little more color saturation and contrast (in the form of more solid blacks). It also exposes more of the image on the finer highlight-sensitive grains, so that it sort of "fills in" the gaps between the larger shadow-sensitive grains. In other words, the result won't look as grainy.

Underrating a stock is easy, 2/3 stop is usually sufficient. Set your light meter to 320 ASA, and at the head of the roll shoot a gray card properly exposed at 320 ASA. The image will naturally be overexposed on the negative, but the gray card provides a reference for the color timer or telecine colorist to set up a proper brightness on the transfer or print.

Don't confuse sharpness with granularity though. An image can be both grainy and sharp at the same time, especially since the grain moves around at 24fps. 7218 is a great stock and you'll have a pleasing looking image even at 500 ASA, although perhaps not as fine-grained as the '17.
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#4 Frank Barrera

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Posted 10 March 2007 - 08:00 PM

which I'm afraid will be too grainy.

If you are going to a print, upon projection you will see some grain as compared to a slower stock. But it will not be terrible. If this is just for video release, well, grain will not be an issue. It will look very tight. This is one of the main reasons why 5218 has become such a popular stock.
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#5 Patrick Cooper

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Posted 11 March 2007 - 03:56 AM

If shooting 500T under tungsten lighting with no filter, setting 320 on your light meter will overexpose the negative. If you are shooting 500T under daylight illumination with an 85 filter in place, setting 320 on your light meter will expose the negative normally.
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#6 Michael Nash

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Posted 13 March 2007 - 03:24 AM

If shooting 500T under tungsten lighting with no filter, setting 320 on your light meter will overexpose the negative. If you are shooting 500T under daylight illumination with an 85 filter in place, setting 320 on your light meter will expose the negative normally.


That's the whole point -- he wants to deliberately underrate (overexpose) the stock to tighten up the grain. "Rating" the film at 320 tungsten, and 200 with an 85 filter.
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#7 Michael Dean Gibbs

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Posted 13 March 2007 - 11:24 PM

[quote name='Michael Nash' date='Mar 10 2007, 03:05 AM' post='159781']

[quote]Underrating a stock is easy, 2/3 stop is usually sufficient. Set your light meter to 320 ASA, and at the head of the roll shoot a gray card properly exposed at 320 ASA. The image will naturally be overexposed on the negative, but the gray card provides a reference for the color timer or telecine colorist to set up a proper brightness on the transfer or print.
[/quote][quote]


Greetings Michael,

Did you really mean to say..."Set the light meter to 320 ASA, and at the head of the roll shoot a grey scale properly exposed at 320 ASA"...or did you mean to set the light meter at 500 ASA for 500T, 7218, and shoot the grey card?

Isn't the disparity between the properly exposed grey scale at 500T and the overexposed footage what tells the colorist that you purposely underexposed the image.

I ask this out of curiosity as I am learning

Thanks,

mdg



[quote name='Michael Nash' date='Mar 10 2007, 03:05 AM' post='159781']

[quote]Underrating a stock is easy, 2/3 stop is usually sufficient. Set your light meter to 320 ASA, and at the head of the roll shoot a gray card properly exposed at 320 ASA. The image will naturally be overexposed on the negative, but the gray card provides a reference for the color timer or telecine colorist to set up a proper brightness on the transfer or print.
[/quote][quote]


Greetings Michael,

Did you really mean to say..."Set the light meter to 320 ASA, and at the head of the roll shoot a grey scale properly exposed at 320 ASA"...or did you mean to set the light meter at 500 ASA for 500T, 7218, and shoot the grey card?

Isn't the disparity between the properly exposed grey scale at 500T and the overexposed footage what tells the colorist that you purposely underexposed the image.

I ask this out of curiosity as I am learning

Thanks,

mdg
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#8 Michael Nash

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Posted 16 March 2007 - 08:11 AM

"Did you really mean to say..."Set the light meter to 320 ASA, and at the head of the roll shoot a grey scale properly exposed at 320 ASA"...or did you mean to set the light meter at 500 ASA for 500T, 7218, and shoot the grey card?

Isn't the disparity between the properly exposed grey scale at 500T and the overexposed footage what tells the colorist that you purposely underexposed the image."



No -- the gray card is the reference for normal color and brightness. If you shot a gray card at 500 ASA and then afterward exposed your footage at 320 ASA, all your footage would come back 2/3 stop overexposed.
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