Color temparatures, sky color, ect. and COLOR SPACE

V-Ray V-Ray for 3ds Max General
1

I’ve been using the 2.2 gamma thing for some time now, but i deliberately avoid using the term LWF since i’m not sure if i am actually working in linear space.

To me, it’s a very simple thing.

1. My renderings were dark and i used all kinds of means to get light in there.
2. Whenever i tried increasing the gamma the whole image would end up getting washed out.
3. In order to compensate for this i applied gamma to all of my textures and colors, so i could get oversaturated images, which would end up looking normal once i increase the gamma on them.

Of course, I notice a lot of issues as a result of this, which i’m probably not attending to properly, especially since i am trying to work with floating point images. But the bottom line is - “i managed to get enough light in there, nuff said.”

What bothers me the most is that whenever i work with gamma of 2.2 my ies lights, and vray skies tend to look very washed out. I figure thats because they can’t be gamma corrected.

Why is this?

I can correct all the textures, otherwise they would seem washed out. The same goes for most of the colors, i can either use color correct or vray color and apply the desired gamma.

The only thing i can’t correct are vray sky, and ies colors.

Please take a look at these two images:

This one has the color temparature applied to an ies light. If i switch back from temparature to color i can read the color of that temparature in RGB. But i can’t correct it since it has no map slot (so i can’t use vray color or color correct).

The room is really… washed out.

But, what i can do is, read the RGB value of that color, and correct it in PS (apply the desired gamma).

The result is, proper… i think. This is how blue it actually gets when no gamma is involved - straight out of the box, gamma 1.

2

You can exclude or include the color-selectors from gamma-correction in your Preferences->Gamma and LUT tab.

Best regards,
Ruud

3

Not sure if i follow.

4

In Max, goto Customize → Preferences → Gamma and LUT check ‘Affect color selectors’.
The vray-sky can be corrected by checking ‘Affect background’ in Vray Color Mapping.

But maybe i don’t follow :slight_smile:

I’m using the same workflow, and never suffer from pale vray-skies. And the IES-lights seem to correspond good to the color-picker.

5

I think you don’t follow :slight_smile:

Think of it this way.

In one scenario, you decide that your vray sky, seen in the background of your image is too pale, because it’s not gamma corrected, before being rendered in a different color space.

Then you tick off “affect background” vray color mapping idalog. Lets say you were using a 2.2 gamma color mapping, then your 3d objects will be placed in sRGB (or whatever the new color space is called) but your sky wont. Inevitably it will be much more intense when seen in the background of your image (behind all the 3d objects).

But, it will still be different (pale in this case, compared to this new look) when seen in reflections, and when it’s actually illuminating the scene.

6

Try rendering an image with an ies light and lets say color of 8000 in kelvins, and you’ll see that it differs greatly when done in LWF and without LWF. No matter what you do with gamma, your colors should be similar, not drastically different as seen in my example above.

*edit*

If i were to show these two images to someone who knows nothing about CG but is an expert in light design, and asked him to pick the one he thinks is close to 8000K, he would pick the blue one, not the washed out one because that one is closer to white, d65 or something like that.

7

hehe, i don’t follow, i agree.

>> …your vray sky, seen in the background of your image is too pale, because it’s not gamma corrected

If you tick ON ‘Affect background’ the vray-sky will be properly gamma adjusted already, just like the rest of the scene. And the reflections of the sky will match accordingly.

Ofcourse the sky won’t match if you don’t use the same color-correction on the vray-sky as on the rest of the scene that is lit with vray-sky and sun.

8

btw, i’m using ‘Don’t affect colors (adaptation only)’ in Color Mapping for that to work correctly.

9

Look, forget about the GI. Place a textured plane somewhere in the scene, and put an image in the enviroment slot. Place the camera so that you can see a patch of both.

  1. Render it straight away without any gamma/LUT nonsense. Save the image.
  2. Then set the gamma/lut to 2.2, but don’t change anything on the textures. Save the image.
  3. Then set the texture gammas to 2.2 (or .45454? i never figured out what exactly is it that you do), render that and save the image.

1. Will show the same textures you would see outside max.
2. Will show two very washed out textures
3. Is in what we call “LWF” (but may not be a part of a linear workflow?) but it will be the same as image 1.

Now add a vraysky in the picture.

Set the camera so you see both the textured plane and a patch of vray sky, dont use any GI instead let it be lit by the default lights (or whatever, just no GI).

  1. Render an image without any gamma/lut nonsense. save it
  2. Render an image with gamma/lut, but don’t correct the texture (leave it at 1.0). save the image
  3. Render an image with gamma/lut, and correct the texture (2.2).

1. Will have a really blue and intense sky, and your normal texture.
2. Will have a washed out texture, and what we may call a washed out sky, at least compared to the first image.
3. Will show the texture exactly the same as in image 1, but the sky will show the same as in image 2.

You have to agree that it’s quite different than what i described in the first example. #3 in both cases should be the same as 1 correct?

This is where i get lost. If we have a need to correct, or change the gamma in our colors and our textures. Why is there no need to do it with vray sky, or kelvins?

10

>> Why is there no need to do it with vray sky, or kelvins?
There is a need to do this. That’s exactly what the ‘Affect background’ setting is for. It applies the gamma-correction to the Vray-sky.

Scenario with vray sky:
4. Render an image with gamma/lut, and correct the texture (2.2).
    In Color Mapping set Gamma Correction to 2.2 and also check ‘Affect background’ and ‘Don’t affect colors (adaptation only)’
This should give you a result (approximately, less energy bouncing) the same as 1.

But i have this nasty feeling we’re still talking in different directions :slight_smile:

Back to your first post: about the color-picker, does changing the ‘Affect color picker’ in Gamma and LUT make a difference for better selection of the proper IES-color?

11

Back to your first post: about the color-picker, does changing the ‘Affect color picker’ in Gamma and LUT make a difference for better selection of the proper IES-color?

Ok, forget about the color picker. Take a look at my two images, which one corresponds to 8000k?

Scenario with vray sky:
4. Render an image with gamma/lut, and correct the texture (2.2).
    In Color Mapping set Gamma Correction to 2.2 and also check ‘Affect background’ and ‘Don’t affect colors (adaptation only)’
This should give you a result (approximately, less energy bouncing) the same as #1.This is a hack. Having the background image done properly is the least of my concerns. Having the sky reflecting and lighting the scene properly is my main concern, and ‘affect color balance’ does not fix that.

‘Apply gamma to vray sky’ would.

12

Ah, yes i think i understand what you mean better now.

But the ‘LWF’-workflow IS a hack. It’s a way to reduce rendertimes by bouncing less energy around and compensating with gamma correction. It’s a way to get good looking results, not neccesarily physically accurate.

But the Vray sun & sky in combination with a physical camera were the base of the workflow. The .255 method Lele describes for instance, is based on whitepoint/intensity measurements with the Vray sun and sky. According to those results, the materials are then corrected to bring them within the proper scope to get ‘realistic’ results.

13

Is your physcam’s whitebalance set to neutral for the 8000K test? I’m getting good results with a small testscene here.

14

Let me simplify it even more. Is it possible to get a light to be 8000K with 2.2 gamma workflow?

15

OK, to me it looks like the ‘washed out’ first picture is more accurate, since this is about colortemperature of a light, and not a colorfilter.

The hotter 8000K should be brighter than a 6500K in the center of the target given the same power, but the edges will be more blue. The whitebalance of your cam will reveal or hide that depending on the chosen balance.

The second image is way too blue in my opinion, more like a colorfilter is used.

colortemps.jpg
colortemps.jpg820×576 49.2 KB

16

double post

17

Any idea why is it so blue without any of the gamma nonsense?

Are you saying that by default, its too blue and saturated, and that you need to wash out your images and your color settings by applying gamma to your images?

This is what max shows by default. It’s pretty blue, its by default, it’s something everyone would get.

This is what it shows when i apply 2.2 gamma to it, something that most people don’t know how to do or don’t understand (myself included). Meaning - you need to tamper with a lot of confusing settings in order to get an image like this instead of the first one.

*edit*

for instance

if i take the first image and increase the gamma in PS i get something thats almost the same as image 2.

You are saying that this is actually correct.

If i were to take a normal image:

And do the same thing:

The result would obviously be wrong..

Are you saying that simply increasing a gamma in an image which has an 8000K IES light in it will make it appear correct, while it’s obvious that if the same thing was done on any other image, it would look washed out?

18

This is because you first tell max your display uses a gamma of 2.2

If you want to see what no gamma correction does, you should also disable the gamma setting in Gamma and LUT, because LCD displays have a gamma closer to 1.0.

Here’s a quick test i did with 6500K versus 8000K, neutral whitebalance, gamma correction of 2.2, adaptation only. Bright white gamma-corrected material. To me this looks quite accurate.

IES-6500k-8000k.jpg
IES-6500k-8000k.jpg968×654 63.5 KB

19

Can you do the exact same test but with everything set to default. No gamma/lut in max, vray or anywhere else. The same image, same settings, 6500k vs 8000k, but without any gamma modifications.

Just as if you had done a fresh install of max, and made a new scene with some lights and these two color temparatures.

20

Yup:

- Max Gamma disabled
- Vray Color Mapping: Gamma Correction 1.0, everything unchecked
- Material bright white 255.255.255, no gamma correction

The top one is vray framebuffer, with view in sRGB-space checked
The bottom one has it unchecked, this is the same result as the max framewindow.

Must say i expected the top image to look like that without sRGB-button on.. but somewhere in my head i must’ve taken a wrong turn, it’s getting late i think :wink:

Time for the real experts to have a say about it me thinks :slight_smile:

(note that for these examples i didn’t aim for proper exposure, just wanted to see the difference between the two lightsources)

1098×985 147 KB