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Couldn't you change the Gamma for all textures at once before you render in iRay by changing it there from 2.2 to 4.4.
It would be nice if DAZ Studio iRay rendering offered an option to chose linear colorspace.
I'm not clear on what you are suggesting. Are you saying to increase the lumens on the two lights and NOT correct the dress gamma to 4.4?
The dress is esha's Little Red Dress. This material version has a darker band at the bottom, so it is not just light fall off that makes the dress darker at the bottom. This is the store promo of the dress texture:
I set any images used in a render back to either 0 or 2.2, more usually 0, if they are at 1.0. The Tone Mapping Gamma is set at render time so if the image Gamma used in the render is set at 1.0 or 0 the image doesn't change. If you set the Gamma in the images used in a render to 2.2 it will darken the images slightly in the render. Setting it to 4.4 darkens them even more with more of the pixels in the image turning dark pulling the colours in the image towards the black end of the histogram.
SSS Mode set to Chromatic can, it seems, cause the transparent rendering for certain values of related properties.
Not that gamma.
You suspect an image is gamma corrected when you open it a looks perfect on your screen, those images will give bright and dull renders. If the texture is gamma corrected you are not in linear space. You have two options, fix it on Photoshop or applying a Image Gamma value of 4.4 in the Image Editor.
The gamma value set in the Image Editor is the gamma assumed to be baked into the image - the render then inverses that to gt a gamma 0 value. Setting it to 4.4 would grossly overcorrect.
I was suggesting that having adjusted gamma's texture, do another render with more light to assess that the dress plays nice on any lighting condition.
What you describe is how it should workd in reality, but here in the Valley, you are wrong, this is a quick render test I have done a while back when researching color calibration in Iray. Color calibration is unnecesary for Iray, but for real world cameras is a must, basically you buy some nice toys with asorted color and take some shots at mid day, when the sun is up and toss them to Photoshop.
For this test I took a random texture from the Genesis 8 Essentials, 01_boyshorts_base_color, which I copied before and duplicated four times, there are 4 identical copies, created 6 planes, 4 of them with one of the copied textures assigned, a applied the values 0, 1, 2.2 and 4.4. Renderer @ ISO 100 EV 13.
So why the grossly overcorrected plane at 4.4 gives consistent result to what you would expect in a real world color calibration test. I won't be giving a biased opinion.
You can do your own test scene.
These are the toys you can buy to color calibrate a camera.
Sorry, I'm not following what you did here.
That makes two of us:)
I was trying to demonstrate that those weird adjustments allow you to produce better renders, and why I come to those conclussions and at the same time, explain how you might setup a scene to do your own testing.
What I did in the test render in my previous post is show a comparison of several gamma values applied to the same texture, it probes that DS or Iray do some unneeded/unwanted adjustments to textures and how neutralize that.
Let me know if you still are not following me and hint me where you are at.
All I see is black, white or grey images with the Gamma 1.0 showing grey shorts and the 4.4 one showing the white background as bluish.
Here are four renders. I changed the gamma in the background image. The first image has Gamma set to 0; second image is set to 1.0; third image is set to 2.2; fourth image is set to 4.4.
If you check the histograms you will see that the first two images are near the same, which is also the same as the original image which is one of my own, the third image has more black pixels and the fourth has nearly all the pixels crushed up at the black end. This is what gamma does it changes the colour gamut, the range of colours used in the image, the higher the gamma the less colours and more black pixels. I didn't touch the gamma setting in tone mapping and it is set at 2.2. I also left the diffuse images for the squirrels at default which a think was 0.
Thanks, I've done further renders with more products & the product is restricted to 1 PA product. Don't know why changing those 3 colors though would cause a alpha checker board pattern but leaving them alone shows a clear visible seam and a color mismatch but not alpha checker board pattern. At any rate, it's not so important and I manually compare the settings between the DO and PA product in the future.
Those results are exactly what you would expect if gamma worked the way you say it does (i.e. properly). If you tell the editor that the gamma of the image is 4.4, it thinks the image is essentially way overexposed, so when going back to linear space and rendering the result ends up super dark (so dark even the white is gray). Gamma 1 is is "way underexposed," so it gets lighter. Gamma 2.2 works normally.
...right?
I saved a Shader Preset and a Material Preset and both save the gamma value, the problem is that DS is ignore the value when you apply the Shader or Material Preset. Looks like you earned another Support Ticket.
The far right image is the one that is correct. Yeah, I know, is darker, but holds all the details. Problem is we are all used to work in gamma space that we believe we are linear space.
I'm working preparing a test scene. I'm not pursuin anything, just wanting to share what I have learnt, but in the end this thread is like church bells, only go the people interested.
I currently have 71 open support tickets. I'll make it 72. Thanks for confirming the problem.
This is an exciting thread. A bit over my head at the moment, but I would like to get up to speed. Looks like some great improvements to both the quality and render performance.
How do you figure?
Technically to work in Linear space you should set all textures that have a 2.2 Gamma setting to 0.45 which is the inverse Gamma of 2.2, add these to your render and then render out at a Gamma setting of 2.2 to bring it back into the sRGB colour space.
https://maddieman.wordpress.com/2009/06/23/gamma-correction-and-linear-colour-space-simplified/
The link you provide contains very useful info and is very valid and is the reason of this thread.
What if I’d tell you the value 4.4 is actually a .4545454545. Would you still think am wrong? Would you believe me the far right image is the right one?
Because he used the magic value 4.4
You could apply the inverse gamma in an image editor to linearise, but that's what DS ois doing - you set the gamma of the image (2.2) and DS applies the inverse value to the image to linerarise it.
4.4 is not a magic gamma correction number. You're not actually applying a gamma of 4.4 to the texture or it would be getting lighter. So we can assume that DS is using gamma correction correctly by converting "gamma 4.4" to linear, rendering in linear space, and tonemapping. This would make the texture dark which is what we see. Except no texture actually uses gamma 4.4. So 4.4 is not the right setting. :\
DS is applying gamma correction in the other direction, I know, this is disturbing.
No, it is applying gamma correction correctly based on what you tell it the gamma of the image is. The gamma setting of the texture is not the gamma correction applied to the texture. The gamma correction applied to the texture to linearize it is 1/gamma. So if the image gamma is 2.2, the gamma correction DS applies is 1/2.2=.4545454545...
If you apply a gamma correction of 2.2 the image gets clearer cause it is a power function. If you apply an inverse gamma the image gets darker. Test this in the tone mapping settings. But the gamma correction in the image editor dialog is applied inversely, which is wrong.
The "gamma correction" in the editor is not a gamma correction. It's Image Gamma which DS uses to calculate the conversion to linear using the formula in my post.
Well I found out my problem alpha checkerboard pattern was a PA setting for their product using 'Diffuse Strength' set to 0.70 but if I dial that up to 1.0 it changes to 'Diffuse Roughness' which then changes value automatically to 0.0. The alpha checkboard pattern goes away on render too. It had nothing to do with this thread's possible bug, although I had hoped that excessively light strength might had made translencency too translucent.
So you don't like examples involving images, let's switch to color involving examples then and forget about image gamma...
Take the nice orange color of this web site, the one with new post count, it is #f59205 in hex or (245, 146, 5), which color would you chose to set in a plane or sphere in DAZ to render correctly... in linear space...
No, I like them a lot. The observed behavior is the expected (correct) behavior.
First, how is this relevant to how DS handles the gamma of textures?