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Help Needed understanding Gamma/LUT Correction


danb4026
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I do not currently have, nor have I ever had, Gamma/LUT Correction enabled.

 

I really just do not understand it's use. It looks like when you use Gamma Correction, you have to apply a gamma setting to your materials, which seems like alot of work.

 

I use 2 flat screen displays, one is a Samsung and the other is an Apple. This further confuses things because I understand they base themselves off different Gamma settings (1.8 vs 2.2).

 

The Samsung is my main display that I run Max off of.

 

Can anyone assist me with its use? Should I use it, how to use it, does it matter whether I use Vray or not?

 

Thanks!

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I'm gonna follow this thread because gamma correction makes my head hurt.

 

Renders/scenes look different in Max than in other apps.

So, if I render a scene in max, it can look a touch too light (or too dark).

Yet if I save it out, take it into photoshop, it can look the opposite (or even okay!).

 

I've been rendering to 32-bit images, saving as HDR, and adjusting in photoshop CS2 or PhotoMatrix Pro.

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Why do you save to an HDR?

 

Doesn't sound like you are using Gamma Correction either.

 

I have downloaded materials and images from places like Vray-Materials.de and the materials have instructions to set the gamma for a particular image at a certain value. The only way to change the gamma for an image included in a material is to have Gamma correction enabled in Max's preferences, otherwise it is a grayed out option.

 

Not having Gamma enabled, I do not know if I am actually using or seeing the material as designed.

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Since I have 32-bit frame buffer option enabled in max, the HDR file format is the 32-bit option that I am most comfortable with.

 

I do have the option ticked in max and I think it's set to either 1.8 or 2.2, but I just feel like I'm making random motions and crossing my fingers and fixing it in photoshop.

 

I honestly don't see how there can be a standard with so many different monitors in the market today, each with their own settings and the need to calibrate, etc.

 

Anyway, didn't mean to dominate your thread.

 

:)

 

[passive mode on]

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I don't like Max's handling of this, but I find that a lot of the time my bitmap textures get washed out so instead of using Max's gamma correction I use Photoshop batch processing to make a copy of the bitmaps to drop the gamma. I think that 0.55 is correct if your gamma correction is 1.8 and 0.45 if it's 2.2 but I'll use whatever looks right. The whole thing is ridiculous - since we're on this whole making-Max-easy-for-the-average-architect thing, and gamma is broken in a very consistent way with mental ray, they should just have a one-button "make gamma work" option that's on by default.

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gamma is broken in a very consistent way with mental ray

 

I disagree. I surprised to find that Mental Ray (Max 2009 / MR 3.6) is set up for linear color space straight out of the box, without switching anything. Which I guess would mean it is broken for anyone not working in linear. at least this has been my experience.

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I don't use MR, I use Vray, which has a Gamma Correction control for Color Mapping. This, of course, is for output.

 

Andrew, it sounds like you leave Gamma Correction off in Max....true? But if you have Max's Gamma set at 1.8, then you must have gamma enabled and set at 1.8.

 

If so, do you then take all of your bitmaps and adjust the Gamma in PS thru the batch editing process you referred to? If Gamma is 1.8 in Max, you set the gamma in PS to .55?

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I disagree. I surprised to find that Mental Ray (Max 2009 / MR 3.6) is set up for linear color space straight out of the box, without switching anything. Which I guess would mean it is broken for anyone not working in linear. at least this has been my experience.

 

Really?! Holy crap, I've got to try this. Thanks.

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Is that a Max plugin or a MR plugin?

 

I'm not sure what it does. Does it provide a real-time render in the framebuffer, that can be adjusted for exposure using its features?

 

How is this different than using photoshop after the fact?

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Seriously now.

 

I've been using bitmap images input set for 1.8 gamma, and render output at 1.8 gamma, and I've been "squaring" my color swatches and using photographic exposure and 32-bit EXR output. This is all in mental ray and I recently transitioned to Max2009.

 

Can anybody tell me whether I'm doing this the right / most current way? My output seems correct, I guess all I'd want is something not requiring a calculator when I want to set color swatches.

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Seriously now.

 

I've been using bitmap images input set for 1.8 gamma, and render output at 1.8 gamma, and I've been "squaring" my color swatches and using photographic exposure and 32-bit EXR output. This is all in mental ray and I recently transitioned to Max2009.

 

Can anybody tell me whether I'm doing this the right / most current way? My output seems correct, I guess all I'd want is something not requiring a calculator when I want to set color swatches.

 

 

This sounds correct as long as you calibrated your system to a 1.8 gamma and you created your textures with your machine calibrated to that. I calibrate to a 2.2, so my configuration looks like it does in this attachment.

 

 

If you are not calibrated, I think I would set it to a 2.2, because I think that is more or less considered default for Windows. Even if you are working on a Mac, I think I would still use a 2.2 because Windows would still contorl what your video card is displaying. I think.

 

As for not requiring a calculator. I beleive Max2009 has a color correct material built into it. Simply click on the assign map type button for your diffuse slot, then select the color correct map type. I am in the process of switching computers, and don't have 2009 installed right now, so I can't look and tell you exactly what it is called. But, ...this map type will allow you to overide the gamma on your colors. In previous versions, you needed to install an additional plug-in to do this.

 

The reason why you need the gamma set to what your screen is calibrated to is because setting the gamma here is roughly romoving the gamma that is burnt into your textures when they were created. If you are calibrated to a 1.8 when you created your textures, then you need to un-gamma them using a 1.8. If you are calibrated to a 2.2, then you need to ungamma to a 2.2. I have no idea why Max seems to have a default of 1.8 ghosted in there. I beleive most of the textures you come accross in collections, and on the internet are created using a 2.2 gamma.

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After all of this discussion, I still do not know whether to have Gamm/Lut enabled or not.

 

Also, all of a sudden, when opening a rendered image in photoshop, it is coming out all saturated. Looks great in Max as rendered, and then when opened in PS its totally saturated.

 

Any ideas?

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"Saturated"? Can you post examples?

 

Are you gamma correcting, or using color mapping with something that gamma corrects? What file format are you using? If you gamma the image in Photoshop If you gamma the image in Photoshop can you make it look like it looks in Max?

 

 

BTW Travis thanks for the tips. I'll try 2.2 on the next project.

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Most of the time I use Gamma Correction color mapping in Vray.

 

But heres the problem, and why showing an example won't help....

 

Any picture file that I open in Photoshop has an orange cast to it. The same picture will look fine in any other photo viewing software I have. If I posted a pic on here, you will not see what I am talking about because when not viewed in PS it looks ok.

 

I cannot find a setting to change that will fix the problem.

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Oh and.......

 

I went into PS's color setting, advanced controls, and checked "Desaturate Monitor Colors By" : 20% and the color is much better.

 

But I dont think that is the right thing to do as a general fix.

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So, I have been tinkering a bit, and there doesn't ever seem to be any solid answer. I have searched these forums about this topic dozens of times, and nobody agrees.

 

The topic gives more headaches in this field than any other topic. I think this topic is the most annoying monster ever created. Frankly, I'm near jumping ship with experimenting with gamma correction. I just keep having the thought in my mind that if SO many people feel so strongly about it, there must be some validity to it's importance.

 

Okay, enough of my venting. My real questions is this: Adjusting the gamma correction in max's prefference works great. I get excellent results in my frame buffer, but once I open the image in PS--every image looks the same. They all apear to have about 2.2. I was more happy with levels between 1.5-1.8. Like I said--the results in the frame buffer are excellent, but it is either all or nothing when it comes to opening the images in PS.

 

The image below shows a screen capture of the PS image on the left, and the max frame buffer on the right. The image open in photoshop is the saved version of the image in the max frame buffer.

 

What am I doing wrong?

 

problem01.jpg

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I am wrestling with the same thing.

The image looks fine in Max but looks too dark or light in photoshop and any other viewing program.

 

I just bite the bullet, render it out as an HDR or EXR, take it into photoshop or PhotoMaxtrix Pro, apply a bit of gamma slowly until it looks 'right', then save it out.

I make a new HDR or EXR (filename_GAMMA.HDR) and then flatten it to 8-bits and save it as a JPG or BMP. I use that one for websites or anything else I need.

 

I'm obviously missing something - either in the program or in my understanding - but I guess I'm not alone.

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