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Gamma Correction
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  • Drendir
  • Posted: 31 May 2008 05:37 AM
  • Location: BELGIUM
  • Total Posts: 801
  • Joined: 09 October 2007 10:11 PM

Hi,

I’m working on a scene, and the gamma settings are as follows:

Gamma: 2

Input Gamma: 0,8
Output Gamma: 1,2

However, when I look at the same image on my laptop, it’s ALOT darker. Now, this is really troublesome cause I’ll have to go plot these renders next week, and I’m not sure which settings are correct to have a decent output on paper.

Every time I render, it’s fine on the screen, however, when printed or plotted, it’s darker.

Are there guidelines to the correct gamma coorection to be found?.. I mean, anyone with experience in this, willingly to share some settings I don’t think I’m up for setting them myself since I’m doing it all wrong, compared to my laptop!

greets,
Boom



Intel 7 - 2.8Ghz
NVidia Quadro 4000 2Gb GDDR5
8Gb RAM
3D Studio Max Design 2012 x64

http://boomerang-productions.blogspot.com/

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  • Location: Minneapolis, Minnesota
  • Total Posts: 453
  • Joined: 27 October 2006 12:54 AM
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Hi Boomerang :) ,

You might want to consider getting something like a ‘Pantone huey,’ ; http://www.pantone.com/pages/products/product.aspx?pid=79 These USB devices are designed to help make your photos, computer screens, renders, prints, etc. more accurate.  Since it sounds like you are going between your laptop, your workstation, and then a printer, -you’ll want to have your different systems calibrated to look the same (note; This can be a subject with a huge amount of info to it, and (I think) it’s a good idea to be sure and read up on / study as much as possible items relating to gamma correction, color correction, tone, print color, etc. I’m guessing you already know this stuff, but I mention it just to be safe ) .

I’ll do giant prints, example; Render in Max using a LWF / (hopefully a :) ) ‘gamma correct’ workflow > then do post work in Photoshop > then go print up glossy’s anywhere from 2’ x 3’ to 5’ x 7.5’ , or sometimes long banners, etc.  And each job can vary tons (going from one studio to another studio, different printers, etc.).

I’m not sure what your complete set-up is, but it sounds like you are dealing with a gamma issue, where your gamma settings in Max are different than what you end up seeing on your computer screen in the final bitmap rendered image outside of Max, -where you are most likely looking at an image that is being displayed for sRGB?  There are a number of different issues here, like; gamma calibration for your computer screen, or gamma settings in Max, or getting your screen image colors to print on an Epson printer the way they look on your computer screen.

The Pantone huey that I mentioned above will not solve all of the issues, and a lot of the differences will come from what screen you are looking at, on what system, in what type of lighting space (outside looking at your laptop, inside a dark studio on an old computer screen, etc. ), and with what type of printer you are using (I’m sure I’m missing other variables too).

If you are using a Windows system, and you want to use a ‘gamma correct’ workflow, then most would use a Gamma of 2.2 in Max.  But, you don’t have to, -you could do your Max work, get a render that you like, and then set-up a pipeline where you get that render to look as close to as possible the rendered image that you first created (no doubt, this can be very challenging, and often -depending on many variables- you may need to ‘eyeball’ / guess at your final product or image).  As far as I know, most rendering engines create / use a ‘linear’ space (’math’ ? ), -and gamma settings have been used to help get the rendered images to display well for all of the different systems / screens.

When you work with Max, and use the 2.2 gamma, you are working in a ‘gamma correct’ space.  All of your Max images will look brighter.  Once you take your image out of Max, and look at it in Photoshop, or on a different system, do a print of it, etc. your image will look darker.  The image needs to be ‘corrected’ / adjusted for looking good on gamma displays that are (most commonly) sRGB (at the 2.2 gamma).  It’s kind of like, Max gamma 2.2 = makes the Max workspace brighter, which outside of Max = makes the image look darker.  To keep the image from looking darker, -a starting simple method could be used of- , take the image into Photoshop (and as long as the Color Settings in Photoshop are; Working Spaces > RGB : Monitor RGB - sRGB IEC6.. etc. (or you might be using the very popular Working Space of Adobe RGB (1998) ), then adjust it’s gamma by .4545 ( errr.. Edit, note, this could be an adjustment of applying a gamma correction of 2.2, -since it will depend on the render & the set-up you have for it in Max.  And many people like the adjustment value of 1.8).  But, most likely, this will look ‘washed-out’ or too bright (at first).  If you are saving out images at 16 bit/channel (or 32bit/channel), this is where you will (or could) get into ‘knee,’ ‘crushed blacks,’ ‘gain,’ -as you adjust your image to 8bit/channel.  Photoshop CS3 has a nice feature for this when you go from 16bit/ channel (or 32bit/channel) to 8bit/channel.  Photoshop > Image > Mode > then select going to 8bit/channel = ‘HDR Conversion’ pop-up dia. box > drop down menu > Local Adaptation, and using the ‘Toning Curve & Histogram’ for tweaking.

Some links that might help;

http://mymentalray.com/wiki/index.php/Gamma
http://forums.cgsociety.org/showthread.php?f=2&t=610790&page=1&pp=15 (<-- this is long, but it’s a great thread on it).
http://www.ypoart.com/tutorials/tone/index.php
http://mysite.verizon.net/spitzak/conversion/index.html
http://mentalraytips.blogspot.com/
http://www.digitaltutors.com/store/product.php?productid=3470&cat=5&page=1 (<--click on the “Sample Lessons” in the above right )
http://www.normankoren.com/color_management_2A.html
http://toi.bk.tudelft.nl/maya/he...rchGuide/arch_camera.html
http://www.openexr.com/
http://en.wikipedia.org/wiki/Gamma_correction
http://toi.bk.tudelft.nl/toi-ped..._Mental_Ray:_Tone_mapping
http://www.poynton.com/GammaFAQ.html
http://www.normankoren.com/makingfineprints1A.html#gammachart
http://www.4p8.com/eric.brasseur/gamma.html#solutions

Hope that helps (Ack.. a lot of info there.. sorry).

And, GREAT blogspot Boom! :) Very cool to see your work.

(note:  I do not consider myself an expert with any of this, so I’m completely open to any and all corrections / feedback, etc.)



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  • Drendir
  • Posted: 31 May 2008 03:05 PM

I owe you one, thank you very very much. This is going in the bookmarks



Intel 7 - 2.8Ghz
NVidia Quadro 4000 2Gb GDDR5
8Gb RAM
3D Studio Max Design 2012 x64

http://boomerang-productions.blogspot.com/

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  • Location: Minneapolis, Minnesota
  • Total Posts: 453
  • Joined: 27 October 2006 12:54 AM
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Hi Boom :) ,

I was just pointed to Jeff Patton’s latest blog; http://jeffpatton.cgsociety.org/blog/ .  It’s got some good tips on the LWF creating low contrast renders & how to avoid that (good to check-out, I think).



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  • Drendir
  • Posted: 06 June 2008 06:14 PM

I actually’ve read that blog this morning ;) but thanks!



Intel 7 - 2.8Ghz
NVidia Quadro 4000 2Gb GDDR5
8Gb RAM
3D Studio Max Design 2012 x64

http://boomerang-productions.blogspot.com/

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I appreciate your tutorial with the link,cheers in advance



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