Lighting to the LUT

[adonaisnavarro]

How important is it to “light to the LUT” For example when using a 2383 Print Emulation LUT, is it really important to be monitoring and lighting through that LUT or can it be something changed in post?

Another question is should I be changing my iso according to my camera in order to “shift” my dynamic range depending on the scene and what information I’d like to retain or not retain?

How common are exposure compensation LUTS (-1 stop, +1 stop, etc) or CDL’s used on set?

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[dmullenasc]

What is the alternative to “lighting to the display LUT”?

Because lighting by viewing a flat log image — i.e. no display gamma LUT applied — isn’t necessarily going to give you more accurate results. Log images usually place the highlights rather low in the IRE scale in order to hold bright detail in the overexposure range, so if you light by looking at a log image, you tend to overexpose it in order to make the whites look white and the highlights look bright enough.  Even in the days of photochemical post, you lit negative film based on how it would look in a contact print, which is a form of a LUT, limiting the dynamic range to what the print stock can display, which is why you lit for that range, not for what the negative could capture.

For the most part, using a P3 theatrical display LUT is fine if the final result is both for a film-out and a DCP. The Print Emulation LUT is mainly just to make sure you don’t push colors in color-correction outside of the reproduction capability of Vision print stock, it’s not particularly a “print look” LUT, it’s more of a technical limit to color space.  It would be hard to think of a lighting situation where you would need to work within that limit, you would just have to keep in mind in deeply colored lighting situations that the colors in a film-out to be printed will be limited by what the print stock can reproduce.

[Stip]

Another question is should I be changing my iso according to my camera in order to “shift” my dynamic range depending on the scene and what information I’d like to retain or not retain?

How common are exposure compensation LUTS (-1 stop, +1 stop, etc) or CDL’s used on set?

If you are shopping raw, changing your ISO is essentially the same as using a compensation LUT. All it does is change the brightness of your preview image (which will then change your exposure behaviour).

It’s quite common to lower ISO a stop, or even two, for low light scenarios if you want to retain more shadow detail. In very bright scenarios you might want to raise ISO to protect highlights from clipping. Some raise ISO for creative reasons, to get more of the camera’s specific noise/grain texture.

So if you’re shooting raw there is no need for compensation LUTs, shoot under the show LUT (the look for the project that has – hopefully – been established before shooting) and use ISO to shift more of the DR below or above middle grey if needed.

Shooting to a codec I think it gets a little more complex, as different cameras/codecs react differently to ISO changes.

[Author]

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