1. Join Date
    Mar 2007
    Posts
    39
    #1

    Why use Gamma/LUT correction ???

    Dear all, please reply and share your ideas with me otherwise I am about to go mad. Please help me !!!

    Since a month ago, I was never using Gamma/LUT correction enabled and having really nice and quality renders. Then importing them to PS to make them look better. It was working pretty good.

    Then I enabled gamma/LUT correction to 2,2 just as everybody using this. I do the things that commonly told and I watched too many tutorials. I gamma correct all of the textures and shaders/materials to 2,2. Render in VFB where sRGB is enabled. I use exponential and/or linear multiply just as described in many of the tutorials. But the results I get are always very close to horrible, almost terrifying.

    Except for this gamma/LUT correction issue, I am not a newbie in 3ds max but not an expert also. I can do some satisfying works but with gamma/LUT correction enabled, I am just like the first day with 3ds max.

    Am I supposed to or have to enable gamma/LUT correction for much professional renders? Is it fatally necessary?

    Please help me. I am stuck at this and completely desperate.

    Please see the renders below. The first one is not gamma/LUT corrected and rendered with exponential colour mapping

    The second one is gamma corrected and linear multiply is the colour mapping

    [IMG] Uploaded with ImageShack.us[/IMG]

    [IMG] Uploaded with ImageShack.us[/IMG]
  2. Join Date
    Dec 2009
    Posts
    2
    #2

    same problem with me also any body can slove this problem send mee message plz
  3. Join Date
    Jan 1970
    Posts
    146
    #3

    hello opaque ,....
    man i work with 3d about 5 years and now i use the LWF and see the difference ...
    whitout gamma i make a lot of corretions in PS with light levels and etcs...
    sure you have to learn somethings all new ...
    only see the renders you post the 1 is very nice ... the 2 is horrible .. hehe ...
    looking about lights
    now to get a renders more professionals is only way ..
    study study study ;;;.
    or make the curse of master class 3D
    you make the looking around and see how the things react about light and etcs..
    the pratice ..
    when i learn to make good modelings i realized man,... the textures and lights is the make the diference in the scene .... sure a good model too all is walk side by side....
    but the shaders is almost everything.... rs..

    Hugs friend and good study...
  4. Join Date
    Aug 2010
    Posts
    40
    #4

    see it's very simple with gamma 2.2
    i am giving you to links one for ext. and other for interior but i think you are not saving your final img. in 2.2 carefully save your final img as 2.2 option is on in saving window otherwise your img will be dull
    http://www.cgdigest.com/vray-exterio...rial/#more-400
    http://www.cgdigest.com/linear-workflow/
  5. #5

    Watch this tutorial .. maybe useful the first lesson is Gamma Correction

    http://golden-cg.com/index.php?optio...gory&Itemid=75
  6. Join Date
    Mar 2007
    Posts
    39
    #6

    thank you for all of the help and advices. I do practice almost everyday but unfortunately I dont get any step forward. I already gamma correct all of the textures and shaders to 2,2. I also save the final image with 2,2. I don't know what is wrong with my renders when I use LWF. I am at the place where there is no improvement. I study all of the tutorials I find on the web. I already do what they say. There must be something missing but what. I have never had such a difficulty in learning something. Hope I will overcome this but I dont know how.

    Thank you again for trying to show me the right way. All appreciated.

    Rgds

    Edit: While studying on the renders, and with the help of the hanivray's very useful tutorial link, I realised that I am applying gamma 2,2 double times. Such as; I was selecting linear multiply and adjusting its gamma to 2,2. I also hit sRGB button on vray frame buffer and that makes the image too bright. Instead, I adjust the gamma of Linear multiply as 1,0 in colour mapping and when I hit sRGB in vray frame buffer, the image looks more accurate. Is it the right thing to do? I mean to leave Linear multiply gamma 1,0 is correct or shall I also adjust it to 2,2 ?

    I also apply color correct modifier to all of the materials. For example I apply a pure white colour to the walls and I hit the square next to diffuse and apply ColorCorrect modifier and make it 2,2. Is that right?

    Thank you
    Last edited by opaque; 2011-04-27 at 03:13 PM.
  7. #7

    i am glad that my tutorial was useful for you. yes it is right also to use Linear to 1 and then use sRGB. it is possible but is not the right way. it all depend on your scene. i will come with new tutorial about rendering settings in Vray soon. i will provide it to you when it be ready then u can understand better.
  8. Join Date
    Mar 2007
    Posts
    39
    #8

    Quote:
    Originally posted by: hanivray
    i am glad that my tutorial was useful for you. yes it is right also to use Linear to 1 and then use sRGB. it is possible but is not the right way. it all depend on your scene. i will come with new tutorial about rendering settings in Vray soon. i will provide it to you when it be ready then u can understand better.
    Thank you very much for your interest. I cant wait to see your rendering tutorial. I also need to know how you colour correct the simple colours. For example, you modeled an interior scene and assign no material or shader but a simple white colour from the diffuse colour to the walls. Do you let it stay as it is or do you color correct it also? I have a pluging called ColorCorrect and add it to diffuse stack. Then adjust the gamma to 2,2 by this plugin. Is that ok?
  9. Join Date
    Mar 2007
    Posts
    39
    #9

    dear all, please download the small sized video below in which I tried to demonstrate what I basically do when texturing and rendering with linear workflow. Please comment if there are missing steps or if you have better ideas. I believe that, thanks to your valuable comments and helps, I will leave this problem to history. Below is the link and sorry for the bad quality in order to reduce the size.

    https://rapidshare.com/files/4595774...se_comment.rar

    Thanks in advance

    Rgds
  10. Join Date
    Mar 2007
    Posts
    39
    #10

    hey mates, please help !!!

    * I apply vray color to basic diffuse colors and make them 2,2
    * I apply all of the textures 2,2 gamma
    * I select Linear workflow in the render prop., let bright and dark stay as 1,0 and change gamma to 2,2. Only tick affect background
    * Enable vray VFB
    * Hit sRGB to see the accurate image
    * Hit render

    Very much bright and washed out results. Why? No matter how much I decrease the light multipliers, down to 0,025, the image is always bright and washed out. Why?

    Madness is soo close.
  11. #11

    Quote:
    Originally posted by: opaque
    hey mates, please help !!!

    * I apply vray color to basic diffuse colors and make them 2,2
    * I apply all of the textures 2,2 gamma
    * I select Linear workflow in the render prop., let bright and dark stay as 1,0 and change gamma to 2,2. Only tick affect background
    * Enable vray VFB
    * Hit sRGB to see the accurate image
    * Hit render

    Very much bright and washed out results. Why? No matter how much I decrease the light multipliers, down to 0,025, the image is always bright and washed out. Why?

    Madness is soo close.
    seems you didn't understand Gamma well. i think u are double applying Gamma..once try render it with gamma 1 in Linear workflow
  12. Join Date
    Mar 2007
    Posts
    39
    #12

    Quote:
    Originally posted by: hanivray
    seems you didn't understand Gamma well. i think u are double applying Gamma..once try render it with gamma 1 in Linear workflow
    Please help me find my mistake then. In every tutorial I have watched I see people adjust the gamma in color mapping to 2,2. Now you tell me that apply 1,0 instead.

    Where may I have apply double gamma? I just adjust the Gamma / LUT settings as enabled and to 2,2. And also 2,2 in color mapping. No other gamma adjustments. And all of the tutorials I saw adjust just the same settings.
  13. Join Date
    Mar 2007
    Posts
    39
    #13

    Alright, here is what I do to get the best results;

    * Enable Gamma/LUT and put 2,2 for system gamma. Enable Affect materials and other. Input image to 2,2 and output image to 1,0.

    * Select Linear multiply from the color mapping tab and give all 1,0 value including the gamma. Select affect background and Linear workflow

    * After rendering, save the image with 1,0 gamma as a open exr.

    I dont know if this is the right way but this is the best way I found so far. This way, I dont apply gamma 2,2 in the color mapping tab and also while saving the image.

    Any comments will be highly welcome

    thanks in advance
  14. Join Date
    May 2010
    Posts
    41
    #14

    select affect background but not linear workflow tick since the latter is put there to help people who haven't done their previous works with the linear work flow in mind. if you put 2.2 in color mapping then don't click srgb in vray frame buffer if you do you apply double gamma to your render of course all of this is for viewing purposes. the main issue is when you save it you don't need to apply another 2.2 to your render if you choose 2.2 in your color mapping. you can change it in post work by applying inverse gamma to your render I suppose. but why all the work?
  15. Join Date
    Mar 2007
    Posts
    39
    #15

    Quote:
    Originally posted by: swarthykhan
    select affect background but not linear workflow tick since the latter is put there to help people who haven't done their previous works with the linear work flow in mind. if you put 2.2 in color mapping then don't click srgb in vray frame buffer if you do you apply double gamma to your render of course all of this is for viewing purposes. the main issue is when you save it you don't need to apply another 2.2 to your render if you choose 2.2 in your color mapping. you can change it in post work by applying inverse gamma to your render I suppose. but why all the work?
    thank you very much. You have one of the best information for me. After reading your comments, I realized that I took a step forward. Thank you very much again. Please comment also on the followings in order to confirm if I got it right. You may feel like talking to an idiot but please nevermind and help me once again step by step. Thanks in advance.

    1- Since I do all of the previous works, I will not select Linear workflow in the color mapping tab. I will only select linear multiply and affect background

    2- If I apply 2,2 gamma to linear multiply in the color mapping tab, I will not enable sRGB in the VFB. In this case, if I apply 2,2 gamma and dont enable sRGB, I will save the image with 1,0 gamma and as open exr (or whatever)

    3- If I dont apply 2,2 gamma and let all values stay as 1,0 and select linear multiply with affect background in color mapping, then I will enable sRGB in the VFB. In this case, if all of the values stay 1,0 in color mapping and sRGB is enabled in VFB, I will save the final image with 1,0 gamma OR 2,2 gamma?

    Please just tell me, step by step, the two ways from the beginning to saving. Color mapping 1,0 and Color mapping 2,2 procedures. I hope to have your valuable help in the soonest.

    regards
  16. Join Date
    May 2010
    Posts
    41
    #16

    I am sorry I haven't checked here and I don't receive messages from evermotion for the replies I get and I don't know how to activate it if there is such an option. For the questions you asked here are my answers if you haven't got the hang of it already.
    1 If I were you and did all my previous works without the LWF on mind, I wouldn't check that stupid tick on colour mapping anyway. It ****s everything up, in a nutshell. I would reload my each and every texture from the beginning with the option 2.2. This way you bring all your textures to 1.0 gamma.
    2 As I can see you got the hang of it. I don't know much about exr. But if you are working with linear colour mapping exr is the best option for compositing purposes. I prefer reindhard.
    3 That's right.

    I don't know if you know anything about linear space. 3ds max and vray work in linear space. When you load your bitmaps to 3ds max which are mostly from internet and gamma corrected to be seen on computer monitors properly you need to pull them back to linear space by applying inverse gamma to eliminate the gamma to make them in the same space in which your software works so that everything is under your control. In 3ds max's gamma and lut settings you tell your software that you want to view the output in srgb space which is mostly internet. However vray frame buffer is an exception from this teaching and you need to teach it separately if you choose gamma 1.0 in your colour mapping settings. If you choose 2.2 you shouln't click srgb option on vfb since it applies gamma twice and you need to save it as it is. That way you burn the gamma out of 3ds max. That is the path I would recommend because vray is adaptive and place samples according to their priority and if it sees any darkness it doesn't place enough samples on areas that is actually not really dark.
    Test it for your self and choose 1, render and apply gamma then choose 2.2 apply no gamma and compare the two images you will see what I am talking about in terms of grains.
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