lin2log LUT?

V-Ray V-Ray Common Public
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1

Hy all!

I am trying to create a new workflow for myself that could be very useful, but I am stuck.

I need a LUT that converts from linear to LOG to later do a specific post process on the LOG image.

The thing is that I find all kinds of luts from lin to rec709 or log to rec709 and similar, but I find absolutely nothing related to a lin2log lut (any LOG will do: S-log, V-log, G-log…).

I could do it in Davinci which has lin to log converters, but I want to have a LUT to use it in VFB and be able to do the tests very fast without having to go from max to Davinci and back.

Does anyone have such a lin2log LUT or have any idea on how to get a LOG output directly in the framebuffer?

Thanks in advance!

2

You get some luts with Resolve:
C:\ProgramData\Blackmagic Design\DaVinci Resolve\Support\LUT\VFX IO

is it just for preview or are you outputting log encoded files?

3

Hello Marcin,

First of all, thanks for pointing out the DaVinci conversion LUTs.

I’m trying to develop a proper workflow to test how linear images rendered from V-Ray, for example, can benefit from editing and color correction in a LOG format.

I am very used to color grading LOG material and am trying to test how it works with rendered images converted to LOG material.​

4

Support for luts used to be very limited in VFB. Lin to log was not possible via lut, it seems to work now but I’m not sure if everything works correctly.

My old simple way of getting Cineon log curve in VFB was loading “empty” cube file and checking “work in log” option.
Or making custom curve adjustment:
when you save .vfbl file from VFB with curves adjustment layer included, you can edit the points. you can make points linear first, input just “point centre” and than smooth it automatically.
looks like this:

“class”: “chaos.cc.curves”,
“properties”: {
“version”: 1,
“name”: “mP_AgX_KrakenLog”,
“enable”: true,
“expand”: false,
“expandable”: true,
“blend_mode”: 0,
“opacity”: 1.0,
“show_preview”: true,
“curve_graph”: {
“version”: 1,
“Master”: {
“points”: [{
“point_type”: 0,
“point_center”: [0.0001347560901194811, 0.0000720880925655365]
}, {
“point_type”: 3,
“point_center”: [0.00029164133593440056, 0.044006794691085818],
“left_vector”: [-0.00005229508315096609, -0.014576690271496773],
“right_vector”: [0.00002810347177728545, 0.007833539508283139]
}, {
“point_type”: 3,
“point_center”: [0.0003759517567232251, 0.06674453616142273],
“left_vector”: [-0.000028103473596274854, -0.007100209128111601],
“right_vector”: [0.0001734105171635747, 0.04381134361028671]
}, {
“point_type”: 3,
“point_center”: [0.0008961833082139492, 0.1424470841884613],
“left_vector”: [-0.0001734105171635747, -0.014875858090817929],
“right_vector”: [0.00047536217607557774, 0.040778495371341708]
}, {
“point_type”: 3,
“point_center”: [0.0023222698364406826, 0.22634030878543855],
“left_vector”: [-0.00047536217607557774, -0.018413471058011056],
“right_vector”: [0.00047443489893339574, 0.018377553671598436]​…

5

mistake on my part - lin2log luts still do not work in VFB.
your options are “empty lut” or custom curves layer.
or custom OCIO if grading with just luts would be enough.