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

[cpnichols]

cp... wouldn't that method you describe for Photoshop APPLY the SRGB curve to the image when printing --- and therefore apply a monitor compensation curve to a printed image??? That doesn't seem right... you would want to strip the curve out and print more linearly, no?


Oh, and regarding EXR -- I don't think AfterEffects supports that though. Any alternatives?

Right... I guess my explanation could be red that way. Basically, photoshop will make sue that your printer sees your image as you are seeing it on your monitor.

As far as AE is concerned I think there is an EXR plugin for phtoshop which may work for AE as well.

http://www.openexr.com/downloads.html

Not sure if RPF is floating point... I know it is multi-channel, but I don't think it is floating point.

Cineon way be another option for you. Pretty sure AE can do Cineon.... but that is only 10bit Float.

[RErender]

Combustion handles EXR's nicely too

[czoog]

how does one save out an EXR, i don't see it in my list in viz05

btw, rpf can be 32bit FP

-Z

[RErender]

how does one save out an EXR, i don't see it in my list in viz05

btw, rpf can be 32bit FP

-Z

http://www.splutterfish.com downloads

[yeohyip]

Great tutorial.... it has also led me to go through a crash course in gamma correction from various sites, and proceeded to become quite confused.

Are there any general test patterns to check if you're display is correct? Will this one from ballistic's submission site work?

Also, is it possible to do double correction unintentionally and have the image come out too bright (for example if the display was correct without correction, and correction were added)?

Thanks for the tutorial... and I hope you have to time to look these questions.

[flipside]

So your solution is to add more lights, increase the amount of GI, etc... As you know, this may actually increase your rendering time. Now, if you continue to work in "linear space" then you are fine. Which is what most of you do.

Ok, I still don't get it but I'm hoping I don't have to get it. When you say the above (bold text), can you tell me what people don't work in linear space?

I usually also don't try to render my images bright enough, I simply do it in post with levels or screen overlay. When I adjust the curve in VFB, this seems to do exactly the same thing to my image.

[davision]

First of all -- take what I saw with a grain of salt since my gamma research was done years ago and it could have rusted along the way...

yeohip --- I don't think it is possible to have a display that doesn't require some type of correction. The gamma problem is intrinsic to electronic displays... monitors differ in how MUCH correction... but they all need some adjustment--- Keep in mind, I'm not a physicist or optics expert, but I'm pretty sure this is correct.

Secondly -- yes, it is a problem of 'double-correcting' your image... when you read up on Gamma correction and color correction, they usually emphasize -- only gamma correct your image once

Now, flipside...

what people don't work in linear space?

I believe that would be people that are using any type of exposure control in max or in vray with exponential color mapping.... or even linear mapping outside of it's default values. But of this, I'm not totally certain.

[cpnichols]

Ok, I still don't get it but I'm hoping I don't have to get it. When you say the above (bold text), can you tell me what people don't work in linear space?

I don't blame you for being confused... it is actually a simple concept, but it took me a while before it "clicked." The first thing that you need to realize, is that your monitor has a gamma curve on it. in the old days, the that gamma curve was all over the place Today, they tried to standardize it. That standard is called sRGB.

So when looking at images, those images have to undertand that there is a gamma curve and adjust how they display the image to compensate for that by applying (invisible to the user) a reverse gamma curve.

Photoshop does it, After Effects does it, they all do it... you just don't realize it. That is because 99.99% of the people that use computers don't need to know.

OK... the Vray frame buffer does not do that. So, all your images look dark. The first thing that people do is to add more light and more fill. That is not a problem unless you open it in Photoshop with an sRGB correction at which point your image will look washed out. The alternative solution is to apply a gamma curve as Throb has outlined in the frame buffer... then when you open it in Photoshop, make sure you are using an sRGB curve. If you would rather add more light and GI, then you need to make sue your are reading into Photoshop with a Linear correction.

I would experiment with that. Make an image in Vray, open it with Photoshop and make sure you are using a sRGB gamma. Look at the difference. Then, apply the sRGB curve to the frame buffer as Throb outlined and see it it matches your image better.

[Da_elf]

i do all my images as bmp with microsoft paint. i wonder if i can do some curves in there hehehe kiddding.

[czoog]

http://www.splutterfish.com downloads

Thanks Eric!

[throb]

how does one save out an EXR, i don't see it in my list in viz05

btw, rpf can be 32bit FP

-Z

i dunno about RPF so I will mention that EXR is the preferred format for me.
Chris is right

There is a vrimg -> exr converter that Vlado put together for me so i can convert 32bit floating point vray images to exr images.

I will post more later when i have time about the vfb, etc...

[throb]

Great tutorial.... it has also led me to go through a crash course in gamma correction from various sites, and proceeded to become quite confused.

Are there any general test patterns to check if you're display is correct? Will this one from ballistic's submission site work?

this is a good site i think:
http://www.normankoren.com/makingfin...html#gamadjust

Also, is it possible to do double correction unintentionally and have the image come out too bright (for example if the display was correct without correction, and correction were added)?

of course. mistakes can be made. it's up to you to make sure your system is working properly.

I know that exr files are handled well in Digital Fusion and Shake.
They are handled best in Nuke (DD's compositing tool - for sale!) because it's the file format we use for almost everything here.

I have a DVD coming out which will train people on Nuke and I spend a few minutes (about 10) at the beginning talking about sRGB and working in linear color space.

for the VFB...
I use the vray one because it's floating point and can handle this correction. Also, it can stop the data up and down to help figure out exposure things. Additionally, you can have it render where your mouse cursor is. That's very handy!

[Gijs]

Hi Throb,

very interesting, but also very confusing, please read the following:

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.

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.

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

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?

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

[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?

[flipside]

[quote="cpnichols"]

Photoshop does it, After Effects does it, they all do it... you just don't realize it. That is because 99.99% of the people that use computers don't need to know.

Thanks for your patience

But if the VFB does not apply this reversed curve, why is an image in the VFB looking the same as that image saved and opened in photoshop?