From: Kai-Uwe B. <ku...@gm...> - 2005-05-11 11:41:38
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Hi, a question about colour clipping. What I am looking for is a way how to not going over Lab to avoid colour clipping. Speed is a major concern. One problem we run into (in CinePaint) is colour clipping during displaying. A oversaturated channel is not weighted against the other channels, even if the information is available. I put a small comparision together: <http://www.behrmann.name/index.php?option=com_content&task=view&id=35&Itemid=73> regards Kai-Uwe Behrmann + development for color management + imaging / panoramas + email: ku...@gm... + http://www.behrmann.name |
From: Gerhard F. <nos...@gm...> - 2005-05-22 19:47:27
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Kai-Uwe Behrmann schrieb: >Gerhard, > >I forgot to mention value 255 is defined as white in cineon and value 95 >as black. > Kai-Uwe, OK, then I understand what you mean. Not knowing about Cineon format before, I took a brief look at the Cienon web site, and IMO http://www.cineon.com/conv_10to8bit.php sais, that reference white is encoded as 685 (not 255), and black as 95 (as you say). However, these values seem to be only the default values, and my interpretation is, that the defaults may be replaced by individual values, if a different white or black point is more approrpiate for rendering a particular Cineon image to an output-referred color space. This web page also specifies, how the 10-bit Cineon encoding should be converted to 8-bit video RGB encoding, and they specify conversion variants without and with different amounts of soft clipping. The described conversion can be IMO easily carried out with TRCs. But I'm still wondering, which RGB color space they mean with "video RGB". It looks like they assume an RGB color space with (default) gamma 1.7, but they are not perfectly clear about this issue either, since they also seem to call this "linear RGB"? And so far, I could not find a statement, where they would specify any RGB primaries of this video RGB color space. Furthermore, the colorimetric properties of the Cineon color space itself are IMO not specified clearly either. The 10-bit log encoding seem to be specified in terms of "printing densities", where "Printing Density = the density above D-min of the negative as seen by the combination of print film and the illumination of a standard motion picture printer" (according to http://www.kodak.com/US/plugins/acrobat/en/motion/support/dlad/kodak_digital_lad_users_guide.pdf). But which spectral properties do the assumed film and the "illumination of a standard motion picture printer" have? A densitometric match does not necessarily imply a colorimetric match, the same densities may result in different observed XYZ colors for different films. Regards, Gerhard |
From: Bob F. <bfr...@si...> - 2005-05-22 20:11:24
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On Sun, 22 May 2005, Gerhard Fuernkranz wrote: > Furthermore, the colorimetric properties of the Cineon color space itself are > IMO not specified clearly either. The 10-bit log encoding seem to be > specified in terms of "printing densities", where "Printing Density = the > density above D-min of the negative as seen by the combination of print film > and the illumination of a standard motion picture printer" (according to > http://www.kodak.com/US/plugins/acrobat/en/motion/support/dlad/kodak_digital_lad_users_guide.pdf). > But which spectral properties do the assumed film and the "illumination of a > standard motion picture printer" have? A densitometric match does not > necessarily imply a colorimetric match, the same densities may result in > different observed XYZ colors for different films. The problem is that Cineon log is really just an encoding and does not have a well defined color space. The "color space" is primarily determined by the film type which is scanned, and whether it is a negative or print. Kodak publishes default values for each film type that they sell. The most scientific description I have found for film is available at "http://wwwau.kodak.com/US/en/motion/support/h1/structureP.shtml". There is also useful information in the document at "http://www.filmlight.ltd.uk/documents/FL-TN-00-002.pdf". Note that regardless of whether the film is mounted in your 35mm SLR or part of a movie reel, the film is comprised of the same basic stuff so there is likely general value for understanding its behavior. Even though digital cameras are currently the rage, a traditional film camera coupled with a high-quality negative scanner should be able to produce images with much better dynamic range. Bob ====================================== Bob Friesenhahn bfr...@si..., http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ |
From: Hal V E. <hv...@as...> - 2005-05-22 21:49:09
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On Sunday 22 May 2005 01:10 pm, Bob Friesenhahn wrote: > The most scientific description I have found for film > is available at > "http://wwwau.kodak.com/US/en/motion/support/h1/structureP.shtml". Figure 24 and the text describing figure 24 in the above is basically the Ansel Adams zone system. Zero is pure black and X is a specular highlight. Each increment represents one stop. Interesting to see how the more things change the more they stay the same. > There is also useful information in the document at > "http://www.filmlight.ltd.uk/documents/FL-TN-00-002.pdf". > > Note that regardless of whether the film is mounted in your 35mm SLR > or part of a movie reel, the film is comprised of the same basic stuff > so there is likely general value for understanding its behavior. > > Even though digital cameras are currently the rage, a traditional film > camera coupled with a high-quality negative scanner should be able to > produce images with much better dynamic range. Bob is right on the money about the dynamic range of film. Let me add some detail. Most color negative films have 10 to 15 stops of dynamic range. Fuji Reala, which I use, has 15 stops of dynamic range. This is way beyond what is currently possible with single exposure digital technology which at best is about 6 to 7 stops. Color slide film typically has a dynamic of 7 to 8 stops. In high contrast scenes shot with slide film you are either going to blow out the highlites or you are going to lose shadow detail. You can not have good detail in both shadow and highlites and this is clearly true for single exposure digital technology. The old adage is expose for the highlites with slide film and expose for the shadows with negative film. I think that digital technology should be treated much the same way as slides with respect to exposure. In addition color negative film is fairly easy to scan as the density of the darkest (highlites) parts of the negative have relatively low densities compared to the darkest parts of slide film. In the above paper Kodak listed the Dmax of B&W negative film as about 1.8 where as B&W positive film (slides) was about 2.4. For color film these values are about 2.4 for negatives and 3.4 for positives. As you can see the difference in Dmax for color negative vs. color slide film is about 1 which is an order of magnitude. Many scanners manufactures claim to have a dynamic range that will handle Dmax > 4 some making claims as high as 4.6. But this is marketing hype and even the very best can only handle a density of about 3.5 before scanner noise becomes significant. The high Dmax of slides makes them hard to scan as the darker parts of the image will tend to have significant amounts of scanner noise and the noise will be in the darker parts of the image where it is more visible with anything but the very best film scanners. But even with modest low cost scanners color negatives with very high dynamic range can be scanned with very scanner little noise. It is still common for those that are shooting 360x180 panoramas to shoot with high dynamic range negative film because these scenes typically include both the sun and deep shadows. Even with film that is capable of a 15 stop dynamic range these scenes are a real challenge to photograph without loosing some much detail at either end of the spectrum. Digital photographers shooting these same scenes must resort to using bracketed multipule exposures and using special HDR software such as Photoshop CS to get enough dynamic range. Hal |
From: Kai-Uwe B. <ku...@gm...> - 2005-05-23 05:56:29
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Am 22.05.05, 14:49 -0700 schrieb Hal V Engel: > Most color negative films have 10 to 15 stops of dynamic range. Fuji Reala, > which I use, has 15 stops of dynamic range. This is way beyond what is > currently possible with single exposure digital technology which at best is > about 6 to 7 stops. Color slide film typically has a dynamic of 7 to 8 > stops. In high contrast scenes shot with slide film you are either going to > blow out the highlites or you are going to lose shadow detail. You can not On <http://hugin.sourceforge.net/> you can see a panorama of mine shot in my hometown on a very bright day. Velvia slide film was used and scanned with a better Imacon. They claim 4.6 and they have. On the scans the sun is slightly outblown. Detail is everywhere in the darkest parts with a magenta cast. Nearly all my images are processed this way and thus far superior to any digital backs I have seen except of the Spheron HDR scancamera. Slide film can nothing do about insufficient scanners. regards Kai-Uwe Behrmann + development for color management + imaging / panoramas + email: ku...@gm... + http://www.behrmann.name |
From: Kevin W. <hx...@ci...> - 2005-05-23 07:52:09
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Hal V Engel wrote: > In addition color negative film is fairly easy to scan as the density of the > darkest (highlites) parts of the negative have relatively low densities > compared to the darkest parts of slide film. In the above paper Kodak listed > the Dmax of B&W negative film as about 1.8 where as B&W positive film > (slides) was about 2.4. For color film these values are about 2.4 for > negatives and 3.4 for positives. As you can see the difference in Dmax for > color negative vs. color slide film is about 1 which is an order of > magnitude. FYI, Modern motion picture prints are better than those numbers by some margin... Dmax on 2393 is roughly 5... even standard 2383 is 4, see the Kodak web site for details. Kevin -- | Kevin Wheatley, Cinesite (Europe) Ltd | Nobody thinks this | | Senior Technology | My employer for certain | | And Network Systems Architect | Not even myself | |
From: Bob F. <bfr...@si...> - 2005-05-23 13:46:12
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On Mon, 23 May 2005, Kevin Wheatley wrote: > > FYI, Modern motion picture prints are better than those numbers by > some margin... Dmax on 2393 is roughly 5... even standard 2383 is 4, > see the Kodak web site for details. Hi Kevin, I am glad to see you on this list. Since you are here, perhaps you can shed some light as to why the motion film industry (for which color correction and management are vital) seems to have largely ignored color management as standardized by the ICC. For sure, the requirements of motion film provide new challenges to address, but it seems that ICC CMS has adapted to meet the challenges of other industries. Can it successfully adapt to film as well? Bob ====================================== Bob Friesenhahn bfr...@si..., http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ |
From: Kevin W. <hx...@ci...> - 2005-05-23 14:34:54
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Bob Friesenhahn wrote: > For sure, the requirements of motion film provide new challenges to > address, but it seems that ICC CMS has adapted to meet the challenges > of other industries. Can it successfully adapt to film as well? well they are trying ... I have attended a couple of the ICC digital Cinema working group meetings now so they have some understanding of the issues we care about. I guess in the post world most people avoided ICC solutions because they were too complex (processing wise) for the requirements we had. More recently I know a number of places have looked at ICC based solutions but found for whatever reason that they didn't work. This time the ICC have obviously attempted to work out why. More generally: It is worth noting that despite what is considered 'accepted fact' within some industries the video and film world doesn't always agree (you can read this many ways of course :-) but in the real world a great deal of care needs to be taken in understanding the meaning of 'enough bits', 'linear', 'black', 'white', 'gamma', 'dynamic range' etc before you even think about what to do with the colour. I'll also make a point that not all the information on the various websites are always correct, mainly due to the assumptions not being explicit. Our website in particular features older documents that are not clear on some points but that are really hard to change due to IP clearance, etc. Kevin -- | Kevin Wheatley, Cinesite (Europe) Ltd | Nobody thinks this | | Senior Technology | My employer for certain | | And Network Systems Architect | Not even myself | |
From: James B. <jr...@pi...> - 2005-05-23 20:49:27
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(cool. People are discussing motion pictures and ICC in the same place) On May 21, 2005, at 9:40 AM, Bob Friesenhahn wrote: > Up until now, it seems that the film industry has been soundly > ignoring ICC CMS and has instead implemented many proprietary methods > for performing color adjustments on film images. This is in spite of > the fact that color adjustments (a.k.a "grading") are done for every > film and it plays a significant role in the production of each movie. > The necessary color adjustments may be different for a different reel > of film, different scene., etc. > I would say the reason is it hasn't worked very well in the past (for motion pictures). ICC is/was hampered in a couple of areas with respect to using it for motion picture. Just for an example, how about under range? No one has mentioned that in this thread. We often have values "less than zero" It just wasn't ICC's job to deal with that. Other reasons have included tools, I can't get my 4 perf 35mm to stay flat on my Gretag SpectroScan, rats! These things are all changing though. When it works, people will use it. And by the way: On May 22, 2005, at 1:38 PM, Bob Friesenhahn wrote: > > Kodak Cineon recommends a warmer color temperature of 5400K. See the > white paper at http://www.filmlight.ltd.uk/documents/FL-TN-00-002.pdf > for a table which lists the various color temperature standards. This is a funny subject. 5400K is *really* red. I have access to a few film projectors. Admittedly they are not quite like the ones in a cineplex but their light is *no where* near this red. Sticking to the wonky color temperature numbers (my projector is like a black body radiator, what?) the ones I have access to are more around 6000-6300. So then, anybody know why this is "recommended"? |
From: Bob F. <bfr...@si...> - 2005-05-23 21:07:44
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On Mon, 23 May 2005, James Burgess wrote: >> Kodak Cineon recommends a warmer color temperature of 5400K. See the >> white paper at http://www.filmlight.ltd.uk/documents/FL-TN-00-002.pdf for >> a table which lists the various color temperature standards. > > This is a funny subject. 5400K is *really* red. I have access to a few film > projectors. Admittedly they are not quite like the ones in a cineplex but > their light is *no where* near this red. Sticking to the wonky color > temperature numbers (my projector is like a black body radiator, what?) the > ones I have access to are more around 6000-6300. So then, anybody know why > this is "recommended"? The radiant energy accross the visible wavelengths is about as uniform as it can be at 5400K so 5400K is a special case in that regard. If you were scanning some film and your RGB sensors had similar sensitivity, then 5400K would produce the most uniform results. Hotter blackbody temperatures emphasize the purples and blue, while cooler temperatures emphasize the reds. Even 6500K emphasizes the blues a bit. Daylight averages 6500K and incandescent lighting is around 3000K so 5400K is also a reasonable compromise in that regard. The first thing I do when I set up a new computer monitor is to adjust the color temperature so that it is not cranked up to an eye-ball scalding color temperature like 9200K. Bob ====================================== Bob Friesenhahn bfr...@si..., http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ |
From: James B. <jr...@pi...> - 2005-05-24 04:40:07
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Hmmm, do you know for sure that's why they recommend it as a whitepoint? Seems odd to tie your viewing whitepoint to the details of the input side (especially since that means negative in motion picture). Wouldn't you want it to be based on something like the viewing conditions in a theatre? Also most scanners I can think of use silicon detectors which I would think would have a very wavelength dependent response (blue would be very much lower)? I'm not sure I'd call that a reasonable compromise, I don't think there is a workable compromise between those two colors. But I guess I wouldn't think of it in that way. On May 23, 2005, at 2:07 PM, Bob Friesenhahn wrote: > > The radiant energy accross the visible wavelengths is about as uniform > as it can be at 5400K so 5400K is a special case in that regard. If > you were scanning some film and your RGB sensors had similar > sensitivity, then 5400K would produce the most uniform results. Hotter > blackbody temperatures emphasize the purples and blue, while cooler > temperatures emphasize the reds. Even 6500K emphasizes the blues a > bit. > > Daylight averages 6500K and incandescent lighting is around 3000K so > 5400K is also a reasonable compromise in that regard. > > The first thing I do when I set up a new computer monitor is to adjust > the color temperature so that it is not cranked up to an eye-ball > scalding color temperature like 9200K. |
From: Bob F. <bfr...@si...> - 2005-05-24 14:33:32
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On Mon, 23 May 2005, James Burgess wrote: > Hmmm, do you know for sure that's why they recommend it as a whitepoint? > Seems odd to tie your viewing whitepoint to the details of the input side > (especially since that means negative in motion picture). Wouldn't you want > it to be based on something like the viewing conditions in a theatre? Nope, pure speculation on my part. I agree that theater viewing conditions are also important and 5400K is not much different than the 5300K and 5200K recommended for cinema viewing in the US and Europe respectively. It seems that Germany prefers 5500K. > Also most scanners I can think of use silicon detectors which I would think > would have a very wavelength dependent response (blue would be very much > lower)? Do telecines/datacines use a similar detection mechanism? My understanding is that these usually sweep a CRT beam accross the film to be scanned so that data is captured sequentially. This differs from a typical "scanner" in which a CCD captures an entire line or even the entire image at once. Bob ====================================== Bob Friesenhahn bfr...@si..., http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ |
From: James B. <jr...@pi...> - 2005-05-24 16:40:19
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On May 24, 2005, at 7:33 AM, Bob Friesenhahn wrote: > Nope, pure speculation on my part. I agree that theater viewing > conditions are also important and 5400K is not much different than the > 5300K and 5200K recommended for cinema viewing in the US and Europe > respectively. It seems that Germany prefers 5500K. > This is the weird bit. I don't think projectors in either place have this white point. I have measured projectors from Switzerland and the US. > > Do telecines/datacines use a similar detection mechanism? My > understanding is that these usually sweep a CRT beam accross the film > to be scanned so that data is captured sequentially. This differs > from a typical "scanner" in which a CCD captures an entire line or > even the entire image at once. telecine's have in the past used photo-multiplying tubes to collect the light. It's my impression that this technology has been largely super-ceded by using CCD's usually in a linear configuration (not an array). I think its typical to still use a CRT to generate the light that is captured by the CCD's through the film. I don't have any first-hand knowledge of telecines - our movies start out digital! |
From: Justin C. <ju...@st...> - 2005-05-24 16:49:52
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On Tue, 2005-05-24 at 16:40, James Burgess wrote: > > Do telecines/datacines use a similar detection mechanism? My > > understanding is that these usually sweep a CRT beam accross the film > > to be scanned so that data is captured sequentially. This differs > > from a typical "scanner" in which a CCD captures an entire line or > > even the entire image at once. > > telecine's have in the past used photo-multiplying tubes to collect the > light. It's my impression that this technology has been largely > super-ceded by using CCD's usually in a linear configuration (not an > array). I think its typical to still use a CRT to generate the light > that is captured by the CCD's through the film. I don't have any > first-hand knowledge of telecines - our movies start out digital! I think telecine is in a state of flux. I know of one that is a single CCD now but that is relatively new. So the technology is getting much more like conventional scanning and photography. j |
From: Kevin W. <hx...@ci...> - 2005-05-24 17:16:09
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Telecine's and film scanners these days fall into two camps, the CCD camp tend to use Xenon lamps, but some use HMI's some high power LED lights, the CRT camp tend to use some kind of detector like a photo-multiplier and so on. As was already pointed out the CCDs are tri-linear meaning no bayer type pattern and a 'true' full coverage sensor so when we say 4K we mean 4096*3 sensor sites not a fractional amount determined by the filter array (we also mean 6K when we say 6K :-). there are lots of things that need 'negative' values (but not in absolute systems), the most obvious is allowing for out of gamut colours to pass through linear matrix systems when doing RGB type conversions. Kevin -- | Kevin Wheatley, Cinesite (Europe) Ltd | Nobody thinks this | | Senior Technology | My employer for certain | | And Network Systems Architect | Not even myself | |
From: Gerhard F. <nos...@gm...> - 2005-05-23 21:24:00
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James Burgess schrieb: > Just for an example, how about under range? No one has mentioned that > in this thread. We often have values "less than zero" It just wasn't > ICC's job to deal with that. Do you want to say, you deal with negative luminance? Can you please explain this more in detail? In which situations can this arise? Or do you only mean device values, which happen to be encoded as negative numbers? Thanks, Gerhard |
From: Kai-Uwe B. <ku...@gm...> - 2005-05-22 20:22:12
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Am 22.05.05, 21:47 +0200 schrieb Gerhard Fuernkranz: > Kai-Uwe Behrmann schrieb: > white is encoded as 685 (not 255), and black as 95 (as you say). However, Yes you are right here as well as Bob with 685 not 255. > these values seem to be only the default values, and my interpretation is, > that the defaults may be replaced by individual values, if a different white > or black point is more approrpiate for rendering a particular Cineon image to > an output-referred color space. > > This web page also specifies, how the 10-bit Cineon encoding should be > converted to 8-bit video RGB encoding, and they specify conversion variants > without and with different amounts of soft clipping. The described conversion > can be IMO easily carried out with TRCs. No problem to create the curves and the usual RGB clipping casts too. Soft clipping does not help. > But I'm still wondering, which RGB color space they mean with "video RGB". It > looks like they assume an RGB color space with (default) gamma 1.7, but they > are not perfectly clear about this issue either, since they also seem to call > this "linear RGB"? And so far, I could not find a statement, where they would > specify any RGB primaries of this video RGB color space. CCIR 709 primaries are used. > Furthermore, the colorimetric properties of the Cineon color space itself are > IMO not specified clearly either. The 10-bit log encoding seem to be specified > in terms of "printing densities", where "Printing Density = the density above > D-min of the negative as seen by the combination of print film and the > illumination of a standard motion picture printer" (according to > http://www.kodak.com/US/plugins/acrobat/en/motion/support/dlad/kodak_digital_lad_users_guide.pdf). > But which spectral properties do the assumed film and the "illumination of a > standard motion picture printer" have? A densitometric match does not > necessarily imply a colorimetric match, the same densities may result in > different observed XYZ colors for different films. A dim sorounding is assumed , like usual in TV environments. I think with D65 but not shure. > Regards, > Gerhard > > regards Kai-Uwe Behrmann + development for color management + imaging / panoramas + email: ku...@gm... + http://www.behrmann.name |
From: Bob F. <bfr...@si...> - 2005-05-22 20:39:05
|
On Sun, 22 May 2005, Kai-Uwe Behrmann wrote: > > A dim sorounding is assumed , like usual in TV environments. I think with > D65 but not shure. Kodak Cineon recommends a warmer color temperature of 5400K. See the white paper at http://www.filmlight.ltd.uk/documents/FL-TN-00-002.pdf for a table which lists the various color temperature standards. My understanding regarding video is that it uses a gamma of 1.0 and is the linear equivalent to the electrical signal values which would be sent to a display device. Charles Poynton's "Digital Video And HDTV" seems to be a fantastic book on these subjects but I have not sat down and read much of it yet. Bob ====================================== Bob Friesenhahn bfr...@si..., http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ |
From: Graeme G. <gr...@ar...> - 2005-05-23 03:07:07
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Gerhard Fuernkranz wrote: > Furthermore, the colorimetric properties of the Cineon color space > itself are IMO not specified clearly either. The 10-bit log encoding > seem to be specified in terms of "printing densities", where "Printing > Density = the density above D-min of the negative as seen by the > combination of print film and the illumination of a standard motion > picture printer" (according to > http://www.kodak.com/US/plugins/acrobat/en/motion/support/dlad/kodak_digital_lad_users_guide.pdf). I think you'll find it is film color densities. The mapping to CIE is complex (I think I remember someone talking about this very problem at last years CIC. It involved a lot of work characterizing existing film stock.) Cineon is effectively just a "digital film" intermediate format, intended for converting film to digital and back again, not for interchanging with other digital media. That's doesn't mean it's not possible, it just means it's not easy. Graeme Gill. |
From: Gerhard F. <nos...@gm...> - 2005-05-23 09:15:57
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> --- Ursprüngliche Nachricht --- > Von: Graeme Gill <gr...@ar...> > > Gerhard Fuernkranz wrote: > > Furthermore, the colorimetric properties of the Cineon color space > > itself are IMO not specified clearly either. The 10-bit log encoding > > seem to be specified in terms of "printing densities", where "Printing > > Density = the density above D-min of the negative as seen by the > > combination of print film and the illumination of a standard motion > > picture printer" (according to > > > http://www.kodak.com/US/plugins/acrobat/en/motion/support/dlad/kodak_digital_lad_users_guide.pdf). > > I think you'll find it is film color densities. The mapping to > CIE is complex (I think I remember someone talking about this > very problem at last years CIC. It involved a lot of work > characterizing existing film stock.) That's my understanding either. So I'm pretty surprized (or rather puzzled), that the specified (standardized?) method to convert from the film density based log encoding to video RGB only involves 1-dimensonal TRCs. I guess, this can only be a rough approximation. Regards, Gerhard -- Weitersagen: GMX DSL-Flatrates mit Tempo-Garantie! Ab 4,99 Euro/Monat: http://www.gmx.net/de/go/dsl |
From: Gerhard F. <nos...@gm...> - 2005-05-22 21:12:10
|
Kai-Uwe Behrmann schrieb: >No problem to create the curves and the usual RGB clipping casts too. >Soft clipping does not help. > You mean, although this seems to be the standardized method for conversion from log encoding to video RGB, you were not satisfied with the results, right? Regards, Gerhard |
From: Kai-Uwe B. <ku...@gm...> - 2005-05-23 06:46:23
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Am 22.05.05, 23:11 +0200 schrieb Gerhard Fuernkranz: > Kai-Uwe Behrmann schrieb: > > > No problem to create the curves and the usual RGB clipping casts too. Soft > > clipping does not help. > > > You mean, although this seems to be the standardized method for conversion > from log encoding to video RGB, you were not satisfied with the results, > right? I think ICC plays not that role in the game. Most software uses propriarity CM on broadcast and film. It is a simple ignorance of some major ICC members. They think in the old paper fashon not in the digital age ;-) regards Kai-Uwe Behrmann + development for color management + imaging / panoramas + email: ku...@gm... + http://www.behrmann.name |
From: Graeme G. <gr...@ar...> - 2005-05-23 03:27:00
|
Hal V Engel wrote: > On Sunday 22 May 2005 01:10 pm, Bob Friesenhahn wrote: >>Even though digital cameras are currently the rage, a traditional film >>camera coupled with a high-quality negative scanner should be able to >>produce images with much better dynamic range. > > Bob is right on the money about the dynamic range of film. Let me add some > detail. > > Most color negative films have 10 to 15 stops of dynamic range. Fuji Reala, > which I use, has 15 stops of dynamic range. This is way beyond what is > currently possible with single exposure digital technology which at best is > about 6 to 7 stops. Color slide film typically has a dynamic of 7 to 8 > stops. In high contrast scenes shot with slide film you are either going to > blow out the highlites or you are going to lose shadow detail. You can not > have good detail in both shadow and highlites and this is clearly true for > single exposure digital technology. The old adage is expose for the > highlites with slide film and expose for the shadows with negative film. I > think that digital technology should be treated much the same way as slides > with respect to exposure. This is certainly the case at the moment for popular imaging sensors, but who knows how far the technology is going to go ? See <http://www.kip.uni-heidelberg.de/vision/projects/hdr/divichi.html> for one that claims 6 decades (ie. 20 stops) range. See also <http://www.kip.uni-heidelberg.de/vision/projects/hdr/sensorvienna.html> for more interesting approaches. A lower dynamic range, higher resolution (and perhaps lower noise) version of such a sensor would give film a run for its money. Graeme Gill. |
From: Bob F. <bfr...@si...> - 2005-05-23 14:29:31
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On Mon, 23 May 2005, Graeme Gill wrote: > > This is certainly the case at the moment for popular imaging sensors, > but who knows how far the technology is going to go ? Regardless of dynamic range capabilities, digital cameras still have a major shortcoming in that they require a huge amount of data storage. As described by the white paper at "http://www.stwo-corp.com/HD%20RGB%20and%202K%20data.pdf", existing compression mechanisms are not suitable for the big screen. I have seen a 4K digital camera for rent which requires 400MB/second storage capability in order to store a "raw" Bayer format, or 1200MB/second for the common RGB DPX format. This means that we will continue to see significant gains in still-photo capture quality, but without major breakthroughs in compression and/or storage capacity, film will be with us for a long time. I can't imagine crawling through the Indian jungle with the objective of capturing the King Cobra on film while dragging along the trailer required to handle the storage. Bob ====================================== Bob Friesenhahn bfr...@si..., http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ |
From: Kevin W. <hx...@ci...> - 2005-05-23 07:57:03
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Bob Friesenhahn wrote: > My understanding regarding video is that it uses a gamma of 1.0 and is > the linear equivalent to the electrical signal values which would be > sent to a display device. Charles Poynton's "Digital Video And HDTV" > seems to be a fantastic book on these subjects but I have not sat down > and read much of it yet. the one thing as far as colour people go is that video is not gamma 1.0 encoded, nor is it reproduced with the original scene gamma... video gets encoded usign a variety of transfer functions with the undestanding it will be shown in a particular viewing condition. The above mentioned book goes into some detail to cover the details, but needless to say there are a whole heap of standards involved. Not all of which do the correct thing as regards accepted colour science e.g. weightings for luma/luminance. Charles' web site also goes into some of these items. Kevin -- | Kevin Wheatley, Cinesite (Europe) Ltd | Nobody thinks this | | Senior Technology | My employer for certain | | And Network Systems Architect | Not even myself | |