How to get better VRay renders (aka working in linear space)

[throb]

I have calibrated my monitor with an Eye one calibrator from Gretag McBeth. the white point of my monitor is 5500K and gamma 2.2, as advised by our photographer. We have calibrated our monitors here to match with their settings and to be able to see what they see. They explained and showed me that sRGB is a very limited color space, which in fact is true.

sRGB is not a limited color space. Well, anything is limiting should you be working in 8 bit.
The GretagMacBeth calibrators are nice and you have it set up exactly right!

I also calibrated my printer with a hardware calibrator for two specific kind of papers and now my monitor image looks almost exactly like the printout.

Perfect!

Now I understand from this tutorial that I should set color management in Photoshop to sRGB right? Or am I misunderstanding the story?

Correct again

Furthermore, you said to Flipside that his colors look washed out because colors and textures were not set for linear workflow. But if I follow your settings and open a texture in max that I created in Photoshop they look completely different. How do you deal with this then?

My photoshop is doing strange things right now...
I will reply to this later when I am at work.

Can you show us some work that is created using this workflow that shows a more photographic result as you say?

Sure, go watch Stealth this summer. Also look at Day After Tomorrow, IRobot, and many other films that DD has done. We work in this workflow 100% at Digital Domain.

Trixian

One thing I'm curious about is why a gamma adjustment of 2.2. When I fiddle with the spinner in max's gamma tab, I set it to what looks like an even match between the grid and the centre box. I end up with a value of 1.74. This kinda confuses me. In addition to this, what about icc profiles assigned to monitors in the monitor set up part of windows?

2.2 is the gamma that closely approximates the sRGB compensation curve.
It might be wise to get the GretagMacbeth calibrator for a good setup.
It will generate a proper ICC profile if you tell it 5500k sRGB.

Flipside
Since my photoshop is messed up here at home, I will need to check this at work.

rob

[vlado]

One thing you should note is that the standard "gamma correction" thingy applies only to CRT monitors. LCD monitors have a very different response curve, which cannot be described with a single "gamma" number. Basic correction software (like Natural Color that comes with my Samsung LCD monitor) should use minimum two check-points, more sophisticated ones use 6 points (f.e. Liquid Color), my own tests included 10 check-points Images that are gamma-corrected for a CRT display usually appear way too bright and washed out on LCD displays.

Another point of consideration is when you use the images as bitmap textures. In that case, they should not be corrected at all - the actual correction must be applied only to the final rendered image...

Best regards,
Vlado

[Trapezium]

Ok, I haven't used the VRay Frame Buffer too much so I apologize if some of this stuff is basic but here are some observations I've made. Maybe some of you will comment on them. If they aren’t clear pleas ask me to elaborate.

First, once I've set up as described in the tutorial, I can't accomplish lighting that's pleasing to my eye. It’s as if I'm working in an extreme opposite of the "Dark Cicero".

When comparing settings, if I use the Duplicate to MAX frame buffer it's as if the Gamma is double corrected as questioned above by Davision. This may be a bug but if I turn off Gamma Correction in the MAX Preference Settings then it appears to work fine. I also notice that the color correction settings aren’t visible in Monochromatic mode. This is a useless too if the settings aren’t visible.

Also, I find it troubling to correct for an IES sun with the VRay frame buffer similar to techniques described in this thread http://www.chaoticdimension.com/foru...ic.php?t=10323 using Logarithmic Exposure Control.

Rob:
In that case should I just set the MAX Preference Settings Gamma Correction to 2.2 and stick with the Logo Exp Cntrl to accomplish the same effect you’re describing?

Maybe I'm still missing something but are you basically describing how to get the same results in the VRayFB as we would by just setting up the MaxFB with 2.2 Gamma Correction?

What do you see are the major advantages of the VRayFB over the MaxFB now that we have use of Environment Settings Exposure Control within VRay?

I thought I could just sit back and let everyone else ask all the questions and follow along but your tutorial has raised so many questions that I feel I must get clear before finalizing anything else

I have to second the thanks for being so patient. It is truely appreciated.

--Jon

[throb]

Ok, I haven't used the VRay Frame Buffer too much so I apologize if some of this stuff is basic but here are some observations I've made. Maybe some of you will comment on them. If they aren’t clear pleas ask me to elaborate.

First, once I've set up as described in the tutorial, I can't accomplish lighting that's pleasing to my eye. It’s as if I'm working in an extreme opposite of the "Dark Cicero".

are you starting from scratch in a new scene or are you loading in a scene previously created? you must start from scratch with this method.

When comparing settings, if I use the Duplicate to MAX frame buffer it's as if the Gamma is double corrected as questioned above by Davision. This may be a bug but if I turn off Gamma Correction in the MAX Preference Settings then it appears to work fine. I also notice that the color correction settings aren’t visible in Monochromatic mode. This is a useless too if the settings aren’t visible.

Ah, I haven't use the mono mode. I also did not try the dup to max framebuffer. However, Vlado, it seems like a bug that the vra vfb doesn't listen to the max gamma setting. what do you think?

also, I find it troubling to correct for an IES sun with the VRay frame buffer similar to techniques described in this thread http://www.chaoticdimension.com/foru...ic.php?t=10323 using Logarithmic Exposure Control.

guess i should try that tut

Rob:
In that case should I just set the MAX Preference Settings Gamma Correction to 2.2 and stick with the Logo Exp Cntrl to accomplish the same effect you’re describing?

I personally would not. Ideal case is that you are only wanting to affect the viewing of the render, not the render itself.

This is what happens if you render with the settings baked in and then go to compositing:
1) you worked in a non-linear mode because your image (not your viewer!) is correcting for this monitor issue
2) then in your compositing package, working completely in linear float space, your color corrections won't be correct. they will be working as if they are doing a linear correction, but in fact will be doing a NON linear correction because the input data is non-linear.

Maybe I'm still missing something but are you basically describing how to get the same results in the VRayFB as we would by just setting up the MaxFB with 2.2 Gamma Correction?

I just like the vray vfb because it allows me to control where the render happens, and it's a floating point buffer so i can stop the image up and down.

What do you see are the major advantages of the VRayFB over the MaxFB now that we have use of Environment Settings Exposure Control within VRay?

see above #1 and #2.

rob

[Trapezium]

Yes, I'm starting from scratch trying to implement your techniques.

The link isn't really a tutorial just a few methods outlined. I see where you're coming from about not using the MaxFB I'll have to do some more tests to see if I can come up with similar output.

I'll post these bugs in the appropriate section though I suspect Vlado will see them here.

Thanks again,
--Jon

[Trapezium]

Hmmm, the problem I'm having with an IES sun may also be a bug.

Vlado,

If I adjust and use Exposure correction alone it does its job but when I turn on either Color curves or Color Levels the image goes almost completely black. This is with the two set to defaults. IS this a possible bug also?

Another thing is that it apears to turn the Alpha completely black.

This is all hapening with the same settings from the above tutorial.

--Jon

[davision]

Furthermore, you said to Flipside that his colors look washed out because colors and textures were not set for linear workflow. But if I follow your settings and open a texture in max that I created in Photoshop they look completely different. How do you deal with this then?

Gijs, I fairly sure you can set the Input Gamma for the bitmap file (where you load it in) to compensate for the different appearance.

You can also set input gamma in the Max Preferences, but I don't recommend it since it's a global setting and many things will probably get hosed.

[yeohyip]

Thanks for all the answers.

And thanks Vlado for pointing out that LCDs are different. This was probably the source of a lot of my confusion. I found out that my LCD display has 3 different gamma settings built it, unfortunately they are called gamma 1, 2 and 3 without much further description. On gamma 2, the test images looks correct without needing any correction, on gamma 1, using a correction of 2.2 looks correct. I will need to dig up my display manual, hopefully it explains the gamma settings further.

How did you go about calibrating your LCD Vlado?

[davision]

After reading all this stuff, I actually went ahead and tried doing the curve in the Vray VFB. For some reason, my dark areas seem to have no detail at all -- the dark areas are just banding heavily and almost look like an 8-bit image (my image is somewhat dim to begin with).

Why would the curve create such banding? I can understand why it would with a low color depth -- but not floating point.

[Trapezium]

Did you accidentally unclick Force color clamping? Are you using a CRT?

--Jon

[Gijs]

Just read the 3dsmax manual and it says to gamma correct only once. If I understand correctly this means I don't need to adjust max anymore, since the gamma correction is already loaded at windows startup.

I did a few tests with a new file and no matter what I try the images appear very flat, so I think the above is true

[throb]

After reading all this stuff, I actually went ahead and tried doing the curve in the Vray VFB. For some reason, my dark areas seem to have no detail at all -- the dark areas are just banding heavily and almost look like an 8-bit image (my image is somewhat dim to begin with).

Why would the curve create such banding? I can understand why it would with a low color depth -- but not floating point.

i notice the same thing sometimes, but whenever i take the vrimg file and convert it to an exr and load it into nuke, it looks great.

i don't see it all the time however. only sometimes.

[davision]

Did you accidentally unclick Force color clamping? Are you using a CRT?

No I don't believe Force color clamp was turned on. But I'm not using a CRT -- LCD instead. When I use the Gamma setup in Max -- it suggests that I'm on a gamma of about 2.5 . Although I think Vlado mentioned that gamma works a bit differently with LCDs. But I don't think that would explain the banding. I must be seeing what throb sees occasionally.

[v-cube]

Hello Forum

I just downloaded and installed the demo version of Combustion and Digital Fusion, but i am not able to import any exr images i created with the splutterfish output plugin.
Both combustion and DF crash when importing those files, the same applies for some sample images from the official open exr site (www.openexr.com) . I am however able to import e.g. the "still life" image from the section "scanlines".

With the open exr display program from www.openexr.com i can sucessfully view all my pictures.


So my questions are:

-can someone please explain this behaviour?

-how do I set the output settings to create exr contend compatible with the programs mentioned above?

-are there any alternatives to these programs ( I already tried the Photoshop Plugin)?

Thank you very much

Andy

[jujubee]

Thanks Throb for all that useful information.

@Trapezium - "Maybe I'm still missing something but are you basically describing how to get the same results in the VRayFB as we would by just setting up the MaxFB with 2.2 Gamma Correction?"

I notice as well that when I render with Max Default Buffer and gamma set to 2.2 with no other corrections, it images appear the same if I applied your correction settings to the Vray FB. Then again my monitor are defaulted with 'Adobe Gamma' on 2.2 which may have something to do with the color fidelity between the two methods (although I'm not certain about this point.)

So basically I'm getting nearly the same results, except Throb's is 'correcting' Vray's FB. If I just render normally in Max (using Vray), and have the gamma preferences set to 2.2, then I don't seem to need to fiddle with any curve.