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Contrast when scanning a negative

negative scan telecine contrast

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#1 Tom Yanowitz

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Posted 19 March 2015 - 06:14 AM

Hi everybody,

 

So at my school I'm going to have the luck to be the DP of a small short in 35mm.

The worflow is this :

Shoot 35mm

the negative is developped and transfered in both mediocre HD for editing and decent 2K for grading and finishing.

 

I know more or less how contrast works when you get a positive from the negative, that is : shooting the same negative at various EI + the positive give different looks (deeper blacks, more or less contrast in the shadows, less grain, more saturation etc etc)

So I wonder how this applies when you scan the negative directly.

I'll have a 500T, what if I rate it at 250 ?

The guy from the lab told be he scans according to the middle gray chart (if we shoot one)

What about things like blacks, whites, contrast, visible grain, saturation ?

 

Thanks guys !


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#2 Robert Houllahan

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Posted 19 March 2015 - 09:10 AM

In the HD "dailies" transfer the Colorist will set contrast and color balance, I try to keep a HD transfer that I know will get a selects Data scan as close to the film and unclipped as possible This is sort of a "feel" as to how the film is reacting on the Telecine if there are no grey cards, and if there are grey cards I try to get those to grey in the transfer and set contrast so the blacks and hilites are visible and unclipped.

 

The selects data scan will be LOG so it will be naturally much flatter than the REC709 HD scan the idea is that the 12-bits or 14-bits of the linear CCD or CMOS sensor in the data scanner sees the density of the film and maps it into the LOG curve such that there is no clipping throughout the range of the film stocks characteristic curve and the DPX frames have the full tonal range and latitude of the film.

 

In the real world there are times when the film stock has more "information" than the scanner can see and the sensor clips in the shadows or hilites, usually it's B&W stocks that can be hard to scan and often need a multi flash scan to get everything that is there in terms of contrast mapped into a digital file.  Color negative shot "normally" is easy for a Data scanner to get all of the range but if you are stressing the stock with underexposure or overexposure to get a look the selects scan may need to be handled in such a way that the digital file is not clipped.


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#3 Tom Yanowitz

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Posted 19 March 2015 - 09:44 AM

Thanks for all this information !

 

So basically, both my edit and grading files will look flat (mapped with a log curve) but the mid gray will have been placed to the correct level ?

An other way of asking this is : will the middle gray have the same luma level in the digital file whether I shoot normally, or under/expose the negative, before I get to the grading.

And by the way, what is generally that luma level for film scans ? I know that for digital cameras when we shoot log encoded raw, or compressed log, it's around 40%


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