Confused About Applying LUT Filter

karma17 wrote on 5/21/2018, 1:55 AM

I shot some footage in Sony Slog2/S Gamut, and have the Property Settings as:

Pixel Format 32 bit floating, full

Compositing Gamma Video 2.2

ACES Version 1.0

ACES Color Space default

View Transform sRGB

Under Media Properties, I have the Color Space set to the Color Space of the camera: SLog2/S Gamut.

When I try to add the SGamut/SLog2 to Rec 709 LUT Filter, the whole thing goes completely crazy. However, if I dial down the strength to .10, it starts looking normal.

Image with the LUT applied, but strength dialed down to .10.

Image with the LUT applied, but strength at 1.00.

Am I missing something here? When I apply LUTS in Resolve, I've never seen them do something like this. Just not sure what's happening. Probably user error I'm sure.

Comments

Wolfgang S. wrote on 5/21/2018, 5:55 AM

ACES does not require an additional LUT. ACES does the transformation from slog2 to rec 709 or sRGB for you. So it makes no sense to apply both, neither in Vegas nor in Resolve.

fr0sty wrote on 5/21/2018, 12:48 PM

Wolfgang, does this also apply to the rendered output, or just the preview?

karma17 wrote on 5/21/2018, 3:23 PM

Ok, I see that now. Once I apply the Slog color space under Media Properties, it has the same effect as applying the LUT. I still have to play around with adding other LUTS. I do notice in Resolve you can double up the intensity of a LUT through the Key function. So, I guess if you want the option of increasing the intensity of the LUT, you can do it because the LUT filter has the strength slider.

Wolfgang S. wrote on 5/22/2018, 11:05 AM

It makes a difference if you apply a LUT for a Gamma/Gamut transformation - so for example from a HDR PQ footage shot in rec2020 to rec709. In such a case I do not see any sense to apply the LUT with an intensity of for example 0.7

Or if you apply a LUT to generate a specific look - here that can make sense to generate what you wish to have.

But ACES is a color management system (what has the first purpose but not the intention to generate a look). However, one may wish to mix that sometimes.

Wolfgang S. wrote on 5/22/2018, 11:14 AM

Wolfgang, does this also apply to the rendered output, or just the preview?

Both is possible I think.

If you have an appropriate preview system (and that can be a rec709 Monitor or even an HDR PQ monitor) ACES will make the transformation for the preview. The target color space is something that you define in the project settings.

And you can adjust the target color space/gamma in the render settings too, and if you wish in a different or the same way as in the project settings.

So all together a very powerful tool for the future.

karma17 wrote on 5/23/2018, 12:37 AM

I am just curious, but are the filters in Vegas Pro logarithmic? I know in Resolve that you can switch from Primary Wheels to Log Wheels, and those adjustments given you finer control over your adjustments, for instance, lift, gamma, and gain. But is the same true in Vegas? Do some filters give you finer control like that?

Wolfgang S. wrote on 5/23/2018, 4:17 AM

There are not log-Filter in Vegas.