Current Gamma Setting of your Monitor

[TheAllusionist]

It seems that the big movement in Vray rendering and other applications is 'Linear Work Flow' (LWF) and it is complicated at times to wrap your head around it. All though it isn't a new concept, it seems to be picking up momentum, especially with Vray users. While I was looking for information for this I noticed a lot of questions about LCD vs CRT and if they should be set up differently, or even if typical gammas are different amongst the two monitor types.

If the gamma is 1.8 for an LCD opposed to 2.2 of a CRT do we use a ratio of 1 / 2.2 = 0.454 or should work with 1 / 1.8 = 0.555 for our correction modifier? I believe that the formula is right and you divide 1/monitor gamma, but how do you know what your monitors current gamma setting is? Well I found this site and on my LCD it came up 2.21, I will of course round it to 2.2 since the test is rather subjective, you squint at the screen and move a slider, but if you are not the type who likes to mess with monitor settings, etc. this can at least let you know approximately what setting you should use to adjust your rendering out put to match what you see on your screen.

Site for determining what your monitors current gamma setting is:
http://www.tsi.enst.fr/~brettel/TESTS/Gamma/Gamma.html

Sites for Monitor Gamma:
http://redskiesatnight.com/gamma.html
http://www.photoscientia.co.uk/Gamma.htm
http://www.ephotozine.com/techniques...e.cfm?recid=12
http://www.uni-mannheim.de/fakul/psy...mma/index.html
http://radsite.lbl.gov/radiance/refer/Notes/gamma.html


This is not a tutorial on LWF, I do not fully understand the principal, this is just sort of documenting how my thought process broke down the process into something I understand and a relationship of gamma correction and what I think is trying to be applied throughout in LWF.

Since I didn't have time to try this all out in Vray, I took a sample scene for a rendering/material challenge at Vizdepot. Quickly did a preliminary scene set up using MentalRay (Hey I wanted to try the new version out), set my preference gamma correction to 2.2 and used just the gamma correction procedure for saving out the rendering vs not using gamma correction. Not using it, the saved image came out very dark like a night scene, using it, the saved rendering matched my screen rendering very closely. So simple gamma correction is important with or without LWF, but I think this example makes it a bit easier to understand the goal of LWF, where you are applying it to materials as well, not an accurate parallel, but it shows the concept of how a monitor displays differently than the actual values being rendered in physically based environments. So basically the initial step is to set your perference 'Gamma and LUT' tab to have corrections enabled, set the display gamma to the correct figure. The next step is to read up on the tutorials available on LWF and give it a try.

LWF Tutorials:
http://www.gijsdezwart.nl/tutorials.php
http://www.highend3d.com/3dsmax/tuto.../vray/147.html
http://www.chaosgroup.com/forum/phpB...near+work+flow
http://www.chaosgroup.com/forum/phpB...er=asc&start=0
http://forums.cgsociety.org/showpost...5&postcount=37



All credit for the model should go to Jeff Patton and Jason Addy and is from VisDepot's current material Challenge: http://www.vizdepot.com/forums/artic...ticle&artid=55

Official Thread: http://www.vizdepot.com/forums/forumdisplay.php?f=90

The scene has gamma correction applied in ‘Preferences’ and the following images indicate screen shot showing what the screen rendering looked with either of the following. Without gamma correction applied to ‘Render to File’ and with gamma correction applied to ‘Render to File’.

[TheAllusionist]

Added some more links that I had hidden away. Of course anybody with some real knowledge of this topic can feel free to jump in and clarify or set the record straight!

[neil]

Hey Russel. Thanks for this thread. Very informative thread. Thanks for the links. Anyway I generally use Gamma 1.8 and in Bitmap files--input gamma also 1.8

[TheAllusionist]

Neil thanks for the feedback and info on what you are using, and yes, I forgot to mention the gamma correction for the bitmap files in the same preference setting dialogue screen, although just left alone at 1 seems to work well also.

[neha]

Okay, I did some quick tests on LWF today, I rendered a very simple scene with a few white boxes using different combinations of settings.

I wanted to see exactly what effect which setting had on the output and offcourse to get a proper understanding and control of the settings. As the output, I basically got three different renders. I'm attaching all three, and then I'll list down all the different settings I used. Right now, I didn't use any textures, I'll do the same tests with textures applied soon.

Settings with which I got the result as Image 1 (01.jpg):

1. No Gamma correction
2. Gamma correction of 2.2, bitmap input gamma 1, rendered in default VFB, image saved without the output image gamma override.
3. Gamma correction of 2.2, bitmap input gamma 2.2, rendered in default VFB, image saved without the output image gamma override. (I believe this will differ from the previous one if I use textures instead of RGB for material)
4. Gamma correction of 2.2, bitmap input gamma 1, rendered in Vray VFB, image saved without the output image gamma override, linear color mapping.

Settings with which I got the result as Image 2 (02.jpg):

1. Gamma correction of 2.2, bitmap input gamma 1, rendered in default VFB, image saved with the output image gamma override of 2.2.
2. Gamma correction of 2.2, bitmap input gamma 2.2, rendered in default VFB, image saved with the output image gamma override of 2.2. (I believe this will differ from the previous one if I use textures instead of RGB for material)
3. Gamma correction of 2.2, bitmap input gamma 1, rendered in Vray VFB, image saved without the output image gamma override, gamma correction color mapping.
4. Gamma correction of 2.2, bitmap input gamma 2.2, rendered in Vray VFB, image saved without the output image gamma override, gamma correction color mapping. (I believe this will differ from the previous one if I use textures instead of RGB for material)

Setting with which I got the result as Image 3 (03.jpg):
Gamma correction of 2.2, bitmap input gamma 2.2, rendered in Vray VFB, image saved with the output image gamma override of 2.2, gamma correction color mapping.

[neha]

Oh, and for those who have never used LWF and wondering what all this is, I would like to mention what my understanding of LWF method is. I have used it on and off and not regularly, so if anyone finds anything wrong, please feel free to correct me In the gamma tab in preference, enable the gamma correction and set the gamma value to 2.2. Set the bitmap input gamma to 2.2. For vray, in the gamma correction color mapping, the gamma inverse correction will be 0.4545, which is 1/2.2

[neil]

HI. here is some test I am posting in Gamma Corrections. I had seen lots of time many people confused about Gamma and override gamma hence I am posting another snap about override gamma that how to check it during render time. Thanks Neha for the test and informations your had given.

[TheAllusionist]

Good presentation of the materila Neil

[neha]

Yes, thats the 'image saved with the output image gamma override of 2.2' setting in my tests. Although one has to be careful as to what settings you are using. If the gamma is already baked in your image, then again overriding it while saving the image will apply the gamma correction on an already 'gamma corrected' image, like in the third image!