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OK, I know I've had this problem before, and got an answer, but it seems like a work around to me.

In standalone, I pick a colour, and it (more or less) looks like that colour when you render it. In LW, I pick a colour, and it is significantly lighter in IPR. Just to show you what I mean.

This is an object with exactly the same set up and texture in both standalone and pluging. (The gamma in both is 1 with the first Agfa colour profile. In LW CS is set to disabled. )
You can see that, pretty much, they look the same, and in both, the colour picker matches the render.

However, if I go to mid grey (128,128,128 in LW and .5,.5,.5 in Standalone) you can see that this changes. In Standalone, the picker and the render look the same. But in LW, the picker is darker than then the render. Also, LW's picker looks darker than Octanes, and LW's render looks lighter than Octanes.
This progressivly gets worse the darker you get. In this image the RGB in LW is 18,14,16. I calculated what this would be in integer and got the values shown. In Octane, they are pretty much the same, but in LW they are totally different. The picker is indistinguishable from black, and the render is lighter.
Now this all seems like a gamma problem to me. So, even though I know you shouldn't, I tried putting LW's CS into sRGB. I then set the IPR to have it's own gamma of 1. This was the result.
Now I am no expert, but the difference between these two is driving me nuts. A little help, or shedding some light on this would be great.

How do I get to the stage where I can pick a colour, and at least have a chance of it looking like that in the render - as it is in the Standalone version.

Perhaps there is some kind of gamma correction inside the LW color picking functions that I don't use with the plugin, or in the Octane standalone that I don't know. I am going to make some tests to see what could be the problem.

-Juanjo

In the LW side there isn't any gamma correction between LW color picker and the final data plugin send to Octane API. I have added a log for the color picker, and as you can see in the bottom message for a 128,128,128 LW color using the standard picker, plugin send to Octane a 0.50,0.50,0.50 color ... the same as a 0.5,0.5,0.5 color in Standalone.

Anyway I am going to make more tests to see if I can see the issue here. Anybody has a simple scene with this problem in both LW and Standalone formats to test it here?

-Juanjo

If you load the same object in both LW and Standalone, set up the render kernel, camera, image, environment exactly as in standalone, you will see the difference. Any object. Are you saying that when you do it, they look the same, or are you saying they seem to be the same under the hood?

What is your standalone color picker space? ... I think that problem is that in LW you are working in linear color picker space, but in Standalone you have it set to sRGB.

Try to set it to Linear (to match the LW full linear workflow), to see if this fix the issue.

-Juanjo

With the Standalone color picker set to linear, I get the same images with the same settings for a mid gray surface.

-Juanjo

I'lll take a look at that when I get home later today. Thanks.

A few things. Firstly, I can't get changing the colour picker to linear to make any real difference in Octane, but that's ok, because I don't want to change the behaviour of Octane. I want to change the behaviour of LW. The problem isn't getting the renders to look the same between applications, the problem is getting the colours you pick to match the colours that render. In Octane, they do (as long as your camera response is set to something). However in LW, especially down at the lower levels, the picker shows almost completely dark while what is rendering is not.

But here I can't see this problem ... see the image below, you can use photoshop or any other tool to test the color I get in rendering.
This is really a simple scene with the basic material, no nodes at all. I set the gray of the object to 8,16,32,64 and 128 ... and I get a render with 8,16,32,64 and 128 gray levels ... the same as I put in the material.

This is the scene, can you test it in your system?

-Juanjo