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31st March 2013, 23:20 | #18161 | Link |
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As far as I'm aware from my limited research, anywhere between 2.2 and 2.4 is fine. 2.2 is usually suggested for brighter environments (including PC monitors) and 2.4 for darker environments.
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31st March 2013, 23:30 | #18162 | Link | |
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An ambient light scaled BT.709 curve via ArgyllCMS helps compensate for this, in a similar way that sRGB curve does for the PC space. I've heard people say that sRGB shouldn't be calibrated to either, yet if you don't, color management software will change the curve to sRGB anyway on sRGB images. Not exactly same thing for the TV space, but that a lot of content isn't mastered to have natural looking contrast @2.4 Gamma, I still see as a major problem for my subjective viewing experience. Last edited by cyberbeing; 1st April 2013 at 00:49. |
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1st April 2013, 05:37 | #18163 | Link |
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While we are on the subject of gammas, what does calibrating a display to a set gamma with ArgyllCMS do when using the generated 3DLUT (either from yCMS or TI3Parser) with madVR? Also, when using yCMS to generate a 3DLUT, should the GPU gamma ramp be disabled or not?
For example, if the video has 2.2 gamma (for the sake of argument) and you have calibrated your display via ArgyllCMS to 2.4, will madVR then remap the video gamma to your new 2.4 display gamma (hence not changing anything) or will the perceived image have "2.4 gamma" contrast? Do you need to check "enable gamma processing" to see the image with "2.4 gamma"? |
1st April 2013, 06:19 | #18164 | Link | |
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1st April 2013, 06:29 | #18165 | Link |
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I've read in a few places that to properly view images the "correct way", one should reinterpret the Rec709 (approximately "2.2") encoded data as 2.4 without correction. Apparently this is intended to correct for the difference between studio (1000 lux) and regular (4-32 lux) viewing conditions. In this case, would I want gamma processing enabled or not?
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1st April 2013, 16:52 | #18166 | Link | |
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I have the feeling that I'm missing something', because my "madTestPatternSource" is dated 09/04/2009, not exactly new i'd say. I noticed however that the latest MadVR v0.86.1 did not include a "madTestPatternSource.ax", so I still have the one from previous MadVR versions in my directory. Where is this new "madTestPatternSource.ax" available ? Was it released as a seperate file ? Thanks if you could clear this up for me ! |
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1st April 2013, 17:30 | #18167 | Link |
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Look in the first post in this thread.
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2nd April 2013, 17:13 | #18168 | Link | |||
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If your display has more than 10,000:1 contrast, the BT.1886 curve is 2.40 gamma. Quote:
The sRGB specification also defines white at 80cd/m˛ and black at 1cd/m˛, giving you a display contrast of 80:1, which looks ridiculous today. Quote:
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2nd April 2013, 17:51 | #18169 | Link |
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Which colorimeter do you have? depending on the model, it may not even work properly for wide gamut.
My personal approach (although may not theoretical correct. It is easy to use) Argyllcms with dispcalgui - > ti3praser–>madvr gamma depend on the content and my liking. D65 or 6500k hardly matters unless you have reference grade equipment imo . |
2nd April 2013, 18:03 | #18170 | Link | |
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D65 has a CCT of 6504K, but not all measurements that read 6504K are D65. You can have a strong green or magenta tint and still measure 6504K. I suggest evaluating your white balance using dE u'v' values as it will give you the strictest results, and ignores luminance (gamma) errors. Last edited by 6233638; 2nd April 2013 at 18:06. |
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2nd April 2013, 19:37 | #18172 | Link | |
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- BT.709 very clearly uses the term "opto-electronic conversion", while BT.1886 uses the term "electro-optical transfer function". This does seem to indicate that BT.709 defines the parameters for the capture/transfer side, while BT.1886 defines the parameter for the playback side. I am still unsure why they are different, but I assume there's a good reason. - BT.1884 describes "black-compensated gamma", which, as far as calibration software and procedures are concerned, is basically what is referred to as simply "gamma". Black-compensated gamma is equal to simple gamma when the display contrast is infinite (e.g. CRT). - According to BT.1884, the One True Display Gamma©®™ is 2.4. One very interesting thing is that display gamma being 2.4 and not 2.2, this means it is actually different from the sRGB gamma, which is 2.2 (well, approximately). This brings me to an interesting thought regarding madVR: considering that madVR is running on a Windows PC, the defaults should assume that the display is calibrated for sRGB, which is the standard for this platform, and should by default convert the content from 2.4 to 2.2. In other words, for maximum compliance with current specifications, madVR should default "the display is calibrated to the following transfer function / gamma" to "pure power curve 2.20" (IIRC it already does), because sRGB, and more importantly, it should default "enable gamma processing" to "enabled, pure power curve 2.40", because BT.1884. @madshi: I'm advocating a change in the default settings. What do you think of this reasoning? On a related note, it would be useful to have a "sRGB curve" option under the "calibration" tab. It should be extremely easy to implement as it is exactly the same curve as BT.709 but with different coefficients for the linear part. If this is to be implemented then the default setting would be "sRGB curve 2.40" (as 2.2 is just the pure power curve approximation). Last edited by e-t172; 2nd April 2013 at 19:55. |
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3rd April 2013, 01:33 | #18173 | Link | |
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From what I've seen, my Panasonic GT50 plasma also naturally ends up with something close to a scaled BT.709 curve, rather than a power-curve, when calibrated to darker gamma. Only basICColor and ArgyllCMS seem to allow calibrating to an sRGB curve directly, but that's not the point. No matter what gamma you calibrate to, using an ICC profile in color managed software like Photoshop will adapt the gamma curve to sRGB when viewing an sRGB image. |
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3rd April 2013, 13:18 | #18175 | Link |
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I think LAV Video does dithering only when it is needed (e.g. when input is 10-bit and LAV outputs 8-bit). So, when using with madVR, LAV Video does not dither unless you have disabled some output formats in LAV or you have some filters between LAV and madVR which e.g. do not accept 10-bit input.
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3rd April 2013, 13:35 | #18176 | Link | |
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http://forum.doom9.org/showpost.php?...ostcount=12403 @Qotscha: Yes, madVR should only ever need to dither at the output stage, before all the data is send to the display. |
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3rd April 2013, 14:40 | #18177 | Link | |
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4th April 2013, 16:48 | #18178 | Link | |
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5th April 2013, 03:14 | #18179 | Link | |
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5th April 2013, 03:18 | #18180 | Link |
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I may have missed something, but is madshi working on something else like commercials again? He's been online and all but no replies.
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direct compute, dithering, error diffusion, madvr, ngu, nnedi3, quality, renderer, scaling, uhd upscaling, upsampling |
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