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Kenzor
08-25-2011, 03:15 PM
I working with DPXs from a sony F35. Does anyone have the LUT and inverse LUT for sony sLog ? I cant find a copy on their site.

Thanks in advance -k

beaker
08-31-2011, 09:28 PM
It's not quite that simple. What application do you need it for? What bit depth are you going from & to and which colorspace are you going to?

The formula for their curve is in their docs online.
www.abelcine.com/articles/images/pdf/srw_itg_s-log_001_io_en.pdf

Here is formula for slog curve:
(0.432699 * Log10(t + 0.037584) + 0.616596) + 0.03

here is the inverse formula for linearizing the curve(useful in programs like nuke):
pow(10.0, ((t - 0.616596 - 0.03) /0.432699)) - 0.037584

Kenzor
09-05-2011, 05:16 PM
It's a bit frustrating that there a whole bunch of .LUT referenced in the sony doc. But no way of downloading them that i can see.

I'm using eyeon fusion to composite some cg elements in several sequences shot on the f35.

The data I have been supplied is in the form of 10bit dpx's with no converstion applied when the digital plates were ripped from the the camera tape. I belive that this means that I essentally have the raw camera data in sLog form.

When fusion loads the dpx files it promotes them to 16bit int or 16bit (half float). Each fusion node interprets this data as normalised ( i think ) with 1.0 being pure white and 0.0 being pure black.

My plan was to leave the backplate in slog rather than linearize it. ... I'll work with the cg elements in linear space then convert them just before I merge them over the back plate.

so... I think this means i need a normalise LUT which maps a linear colour space in the range of 0 to 1.0 to a slog colour space in the range of 0.0 to 1.0

... I'm going to play with the equations in the the paper and see if I can write a script to generate the LUT files

beaker
09-05-2011, 06:54 PM
I can create a lut for you. Do you want one from slog to what colorspace are you comping in? I'm guessing srgb or gamma 2.2 since you are working in 16 bit int? If your working in 16 bit float then it would probably be linear.

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