what is Gamma Correction

13

Comments

  • Mustakettu85Mustakettu85 Posts: 2,831
    edited December 1969

    Szark said:
    yes no one really know how bright 100% is. Well I asked a while back and the consensus seemed like know one knew. ;)

    Moreover, 100% is different between different light shaders =) And may even change with 3Delight versions - do you remember that, Szark? When all area lights had to be rescaled - I think between DS3 and DS4.

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited December 1969

    Hi everyone,
    (SNIP) so in this sense, it does not really matter if the color picker is gamma-corrected. You just tweak till you like the look.

    That dose not sound 'good' to some one that want's to use DS as a tool for deciding where to place lights in a room. Why I'm very interested in the Uber Light rectangular panels. lol.

    Not put off by that (it look close enough color setting). However I dread the thought of going threw each map in each figure in my scenes, thats what, over a hundred maps per person.

  • Mustakettu85Mustakettu85 Posts: 2,831
    edited December 1969


    That dose not sound 'good' to some one that want's to use DS as a tool for deciding where to place lights in a room. Why I'm very interested in the Uber Light rectangular panels. lol.

    Not put off by that (it look close enough color setting). However I dread the thought of going threw each map in each figure in my scenes, thats what, over a hundred maps per person.

    No, no, you don't need to tweak MAPS - DS will do it for you. But if you use diffuse colour multipliers - like, the colour swatch above your texture map is not white - then you might need to tweak it. Or not. The maps and the lights make the biggest difference. The multipliers... not so much.

    And yeah, you're right, the results of 3Delight aren't that easy to translate back into the "real world" - not with the shaders we have. There may be "industrial grade" arch-viz light shaders that would be measured in Wt or other real units, but I don't know of any. It's the unbiased renderers like Lux that generally get these sorts of tools.

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited December 1969

    Mustakettu85, and Szark.

    That was another confusion (leading to my misconception, that Uber lights don't cast light, it's a surface application of sorts). I thought a "Shader" was a preset/property-set for an object or surface, Not a light ray travel calculator?

    And I still seam to have something wrong with "Gama Correction", and "Gamma" on the Render settings tab.

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  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited June 2014

    Let me put the two suggestions side by side.
    Left; Gama Correction Off, Gamma 1.0
    Right; Gama Correction On, Gamma 2.2

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    Post edited by ZarconDeeGrissom on
  • Mustakettu85Mustakettu85 Posts: 2,831
    edited December 1969

    Mustakettu85, and Szark.

    That was another confusion (leading to my misconception, that Uber lights don't cast light, it's a surface application of sorts). I thought a "Shader" was a preset/property-set for an object or surface, Not a light ray travel calculator?

    And I still seam to have something wrong with "Gama Correction", and "Gamma" on the Render settings tab.

    Everything is a shader. A shader is a little program. A light is a shader, a surface is a shader... even a camera can be a shader (a volume shader, an imager shader...) If a render engine renders something, it does it because shaders told it how to do it.

    Everything looks okay to me with GC on and gamma 2.2. It's brighter, that's normal. It may seem a little "off" to you because you're using all those direct lights that cast all those sharp raytraced shadows sprawling around on the floor... which they don't usually do IRL (and those who light real-life movie sets with tons of spotlights actually take care to "hide" those shadows with stage props!). For a scene like that, to make a more "natural" lighting while keeping the feel, I'd try a sphere with an area light over its surface, in the centre, and an environment light to imitate "bounce".

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited December 1969

    So the fact that the colored spheres, are almost completely washed out, is normal? (it's a genuine question, not a statement)

  • SzarkSzark Posts: 10,633
    edited December 1969

    Yes generally speaking when using GC ON at 2.20 the render will be brighter than with it off so some light adjustments will be needed. I find reducing the overall light to about a third to half works better. I have it constantly on now so I light accordingly.

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited December 1969

    O.k. so cut back on the intensity of the "DzSpotLight"s to a third, and figure out what the rest of the 'New' stuff dose. I didn't mess with them much at all. I dropped them in the same spots as befor with the "Menu" lights, then set Bias 0.1, Ray-trace shadows, and the intensity to the same it was before. (40% each up high in the corners, and 20% each down on the floor).

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  • SzarkSzark Posts: 10,633
    edited December 1969

    no cut back by a third not to a third. :)

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited December 1969

    by a third, douh. that was a typo, lol.

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited June 2014

    Everything looks okay to me with GC on and gamma 2.2. It's brighter, that's normal. It may seem a little "off" to you because you're using all those direct lights that cast all those sharp ray-traced shadows sprawling around on the floor... which they don't usually do IRL (and those who light real-life movie sets with tons of spotlights actually take care to "hide" those shadows with stage props!). For a scene like that, to make a more "natural" lighting while keeping the feel, I'd try a sphere with an area light over its surface, in the center, and an environment light to imitate "bounce".

    that explains why some "Designers" make rooms with lights that just don't illuminate the work space, and/or the lights glare directly into the eyes of the people in the room. They try to mimic the lighting on movie sets, lol

    I actually wanted the floor to have that beam-hitting-it effect. "O" well.

    Is there a "DzLights" thread? or an explanation of these settings?

    Post edited by ZarconDeeGrissom on
  • prixatprixat Posts: 1,278
    edited December 1969

    Sertorial said:
    ...gamma correction fixes a map that was wrong to start with...

    This is wrong. The map has to be right to start with, then gets corrected. :lol:

  • SzarkSzark Posts: 10,633
    edited December 1969

    I think Correction is the wrong word...I think conversion is a better one.

    It is all about getting the best out of surfaces and light, working together to get better realistic results with what we have with the program. GC is even better when using surfaces designed for realism like AOA's Metal Shader and certain lights like DZlights and Uber lights

  • SertorialSertorial Posts: 962
    edited June 2014

    you know, it's kind of annoying that my thread got rather hi-jacked by way too technical stuff and yet my initial question is still not explained clearly so I can understand it. This forum is the New Users Help Forum, remember? I post here deliberately so I don't get in the way of clever people trying to discuss very complicated stuff. And yet...

    Oh well..

    All I really need to know is whether to have gamma correction on or off? Does it depend on whether the maps I am using have already been gamma corrected? How would I know this? What does it mean "mis-labelled"? My maps just have filenames like BreeTorsoM.jpg - what "label" am I supposed to be looking for?

    Post edited by Sertorial on
  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited July 2014

    That's a good one. I don't think that gamma preset (Color Space) is saved in the "Header" of the jpg, rather it is wherever the other info for the surface is saved (tile # of times, gloss strength, etc). Even tho most image formats have such a field in them (Even BMP has a spot for that).

    That and "I like it, because It's brighter" doesn't sell me, when it was supposed to be a dark scene with an over-bright blue beam-of-light. lol

    I guess it boils down to do you like "A" or "B". And a simple non technical answer doesn't exist, especially when asked "Why did Daz leave it that way by default".
    (edit)
    And again, I dread the thought of going threw each map in each figure in my scenes, thats what, over a hundred maps per person.
    It just levees room for accusations that it was what you did and not "the process" that produced the undesired results, lol.

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  • prixatprixat Posts: 1,278
    edited December 1969

    "Why did Daz leave it that way by default".

    I remember when the software I use, first got Linear Workflow.

    All the old work I loaded had to be re-lit. The more complex the lighting the more it was necessary.
    It was often easier to scrap all the lighting and re-light from dark.


    (It might be possible to cook up something to show where 'GC OFF' causes problems...)

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited July 2014

    prixat said:
    "Why did Daz leave it that way by default".

    I remember when the software I use, first got Linear Workflow.

    All the old work I loaded had to be re-lit. The more complex the lighting the more it was necessary.
    It was often easier to scrap all the lighting and re-light from dark.


    (It might be possible to cook up something to show where 'GC OFF' causes problems...)
    Like with the plastic-skin epidemic, lol.

    That Phobe hair takes forever to render. I think I just now got the lights ALL down to 1/3 of there original values. tho things like 6.666 gets rounded up to 6.7, annoying when trying to be accurate.
    (edit)
    And I need to come up on the lights a tad from the looks of it. B.T.W. Morning.

    Post edited by ZarconDeeGrissom on
  • mark128mark128 Posts: 1,027
    edited December 1969

    Sertorial said:

    All I really need to know is whether to have gamma correction on or off? Does it depend on whether the maps I am using have already been gamma corrected? How would I know this? What does it mean "mis-labelled"? My maps just have filenames like BreeTorsoM.jpg - what "label" am I supposed to be looking for?

    If you have gamma set to 1.0, then you should set gamma correction off.

    If you have gamma set to 2.2, then you should set gamma correction on.

    This seems to work fine for me.

  • SzarkSzark Posts: 10,633
    edited July 2014

    Sertorial said:
    you know, it's kind of annoying that my thread got rather hi-jacked by way too technical stuff and yet my initial question is still not explained clearly so I can understand it. This forum is the New Users Help Forum, remember? I post here deliberately so I don't get in the way of clever people trying to discuss very complicated stuff. And yet...

    Oh well..

    All I really need to know is whether to have gamma correction on or off? Does it depend on whether the maps I am using have already been gamma corrected? How would I know this? What does it mean "mis-labelled"? My maps just have filenames like BreeTorsoM.jpg - what "label" am I supposed to be looking for?


    I answered it plainly enough...I think.

    It is your choice to use GC. It isn't something you HAVE to use. But like I said for more realistic results i.e. making the surfaces react to light better, then GC comes in to play but it ISN'T a requirement.

    and it has nothing to do with the labelling in that context.

    How to find out if the texture map has a gamma of 1 or 2.20 I have no idea sorry. My PS doesn't show that sort of info, well not that I know of.

    Post edited by Szark on
  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited July 2014

    isn't that what the slider in the "Image Editor" is for?
    (edit)
    hens the hundred or so maps to check per person, lol.

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  • SzarkSzark Posts: 10,633
    edited December 1969

    no the Image Editor just allows you to overwrite the GC if required.

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited December 1969

    lol. This is getting better, lol.
    The image needs to be correct, before it can be corrected correctly.
    And we don't know how to check to be Shure the image is correct to begin with.
    lol.

  • SzarkSzark Posts: 10,633
    edited December 1969

    do think correction, think conversion. Nothing is broken. Like I said I don't know how to check if texture maps are correct. All I do is switch GC on set to 2.20 and go about making an image. If a particular maps seems to be coming out too dark then I will set the Gamma in the Image Editor to 1.00 for that particular offending maps.

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited December 1969

    and keep an eye on what your doing with the lights, lol.
    (this was done before this thread started, GC off, Gamma 1.0)

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  • kitakoredazkitakoredaz Posts: 3,526
    edited December 1969

    lets concentrate Setorial question ;-)

    1 All I really need to know is whether to have gamma correction on or off?

    A I like "on", and set Gamma value (in render setting) to 2.2 (or your monitor gamma setting)

    it can only circulate Color textures R,G,B corrected to linea color value,
    then render with all value in linea world.

    After that, adjust output picture gamma to see it in our monitor gamma 2.2
    = (gamma value in render setting

    B if you like the "off" , you may better set Gamma value keep "1.0" in Render setting
    (and this is DS default (resotre factory) setting)

    it use image Color value which already adjusted for monitor Gamma 2.2(in our HD)
    (most of image, we see in our monitor are alerady adjusted for monitor gamma,
    or if you draw pic, in your monitor, it means, the image are adjusted gamma for monitor gamma)

    But when render, DS need to circulate in linea world with other light value etc .

    we expect, the aprication auto Correct (or convert ^^;) image color to linea.not monitor gamma.
    but DS just use the image color value (in HD) without Gamma Correct ("Off")
    then after render. but this time, do not adjust Gamma for monitor again.

    (so that Default restore factory Setting, Gamma value ="1.0" in render setting)

    It is somehow cheat, , but it seems reasonable too.

    because, if DS adjust rendered pic Gamma for our monitor value,
    the used image pic value (they are alerady adjusted for our monitor gamma)
    mutiple gamma .

  • ZarconDeeGrissomZarconDeeGrissom Posts: 5,400
    edited July 2014

    "O" and having Gamma Corect On, at 2.2, is not as bat as that one pic makes it look.

    A single UberPanle (1ft x 4ft), test here. 100% intensity, default Falloff Decay at 10,000 Falloff End.
    and another with a border on the edge.

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  • kitakoredazkitakoredaz Posts: 3,526
    edited December 1969

    And it is nonsence to serch way of check curernt texture gamma value etc ^^;

    when said Gamma value, I believe we may need to clear say,
    which aprication, and which tool gamma value.

    About daz studio, in render setting Gamma value, or in DS surface tab, image editor, gamma,
    or monitor gamma, or how change gamma of texture in each 2D image aprications.

    I recommend open "skin image" which you plan to use as Actor skin.
    in Gimp or photoshop etc to see your texture current gamma. (not value)

    you can tweak gamma, in color lever> input. you find Gamma setting.
    and change it save it. next open the image,

    it should be start from 1.00 again. but you can see, the image are changed
    (yes you modified gamma of texture, then it is your current texture gamma .)

    because "gamma" is value , how you modify R,G,B of image, from current status by formula
    1.0 means no modify. keep it as same as before,,,,

  • Mustakettu85Mustakettu85 Posts: 2,831
    edited December 1969

    This post is a yet another answer for Sertorial yet it is informed by everything going on here, and it is meant to be read by everyone who is still confused. Lurkers included (I know you're there! Today or ten years from now...).

    Reiterating (the best I can, and I'll leave it at that):

    1) DS will handle the maps for you. The only thing you may need is check the correction values. That literally takes seconds per surface.

    And even if you are not embracing linear workflow, checking if the materials make sense is a good practice, if you want to be good at rendering. Do not expect that each and every "DS material" on the market is perfect. Not even commercial products are all excellent in that regard.

    2) It is safe to assume that in at least 90 cases out of 100, colour maps were not linearised. They come from photos or digital paintings - which are made to look good on screen, and this is not what the renderer wants. It has "alien eyes" that see colours differently from your eyes.

    3) So you need to set all colour maps to be corrected with "gamma 0", and all strength maps - "gamma 1".

    That's basically everything you have to remember. GC on, gamma 2.2, check if the maps will get the right correction applied. "0" for colour maps, "1" for strength maps.

    4) This is linear workflow, and it's the only mathematically correct workflow. If you want a solid basis for your renders being "lifelike", it's indispensable.

    If you do not care for "lifelike" (for instance, if you do cell-shading ("toon") exclusively) - or if you somehow do want a lot of extra brain-wrecking over how to make your scene "lifelike" - then by all means, you do not have to use gamma correction.

    Let's run this over once again:
    The "raw" colours coming out of the renderer were not made for your eyes or your computer monitor - because the renderer knows nothing about these. It is an alien being with pure maths for a brain. It works in linear space and gives you a linear output that you then should correct to match your monitor - which, in turn, is made to match your eyes. Which are non-linear.

    This is, basically, all there is to this mysterious beast.


    BTW "but DAZ3D left GC off" is not a valid reason. I love DAZ3D (I really do!), but they are not THE authority on everything render-related.

    Not every hi-end 3D program comes with "GC on" by default either. It does not mean anything.

    Remember: there are no non-technical answers because this is all technology! ;D


    Is there a "DzLights" thread? or an explanation of these settings?

    Not to that extent (only an old one when there used to be an issue with the shadows). You could always make a new thread and ask about the settings you do not understand.

  • Scott LivingstonScott Livingston Posts: 4,303
    edited December 1969

    Here's a good article on linear workflow, including a section called "Why Is This Crap So Confusing?" which I can certainly relate to! :lol: It also has some links to other resources on gamma correction aimed at beginners.

    If you find "this crap so confusing" too, I think there are four valid strategies:

    1. Just forget it and stick with the defaults. This may not be the best option, but for many people it's an adequate one. Until fairly recently there was no gamma correction option in DS (this was introduced with DS4.5 or DS4.6, can't remember which).

    2. Research it, study it, finally begin to understand it. The pros know this stuff and it's one reason (among many) that their renders are so good. This is my "long term" strategy but I'm taking it slow!

    3. Take the advice of people who do understand it. There doesn't seem to be a consensus but the majority of opinions (in this thread, and in similar discussions of the subject) seem to favor turning gamma correction ON and setting gamma to 2.20.

    4. Don't worry too much about the underlying theory...just experiment with the settings and find something that works right for you...either overall, or on a per-render basis. Personally I usually start with gamma correction off and gamma set to 1.00. If the scene just doesn't look quite right or if I'm pulling for something closer to photorealism, I usually find that switching gamma correction ON and setting gamma to 2.20 helps.

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