Forums Technical Discussion Difference in contrast of Karma viewport and render

Difference in contrast of Karma viewport and render

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cmoss
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The Karma viewport always appears darker than the render, even when using the same render and OCIO settings.

Here is the Karma viewport:


And here is the Karma render:


I attached an example file.

Why do these not match?
Edited by cmoss - May 17, 2024 16:40:38

Attachments:
KarmaViewport.png (624.6 KB)
KarmaRender.png (197.6 KB)
KarmaViewportBrightness.hip (730.7 KB)

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Enivob
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The viewport is just a guide. You're comparing an 8 bit jpeg screen grab to a floating point EXR color space. What you render is the true pixel value. Click the viewport full range button and adjust the viewport f-stop to match the viewport to the render, but I think most people look past that task and just accept the render is the final look.
Edited by Enivob - May 18, 2024 09:21:14

Attachments:
karma_viewport.gif (189.8 KB)

Using Houdini Indie 20.0
Windows 11 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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tamte
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Enivob
The viewport is just a guide. You're comparing an 8 bit jpeg screen grab to a floating point EXR color space. What you render is the true pixel value. Click the viewport full range button and adjust the viewport f-stop to match the viewport to the render, but I think most people look past that task and just accept the render is the final look.
I disagree, in my opinion seeing the live render in the viewport with the same LUT should look exactly the same as seeing the offline render in e.g. Mplay with the same LUT

Blindly accepting any difference seems ridiculous
Tomas Slancik
FX Supervisor
Method Studios, NY
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antc
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Does the render gallery match the viewport? Or are you seeing a difference when viewing the exr outside of Houdini?

I agree with Tomas that they should be identical. Both images attached to the post are 8-bit (screen grab or not). But 8 (or more likely 10) bit display corrected representations of the 16/32 bit source exr or framebuffer should be the same using the same profiles.

EDIT: I can repro with the attached hip file (live render vs render gallery). Seems like a bug to me.
Edited by antc - May 19, 2024 10:31:50
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Enivob
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It is a BIG problem that SideFX should fix. But it's been that way for several release. There are troves of posts about "Hey, the viewport don't look like my render."

A 1:1 color match is what most end users want out of the product.
Using Houdini Indie 20.0
Windows 11 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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