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Micha Clazing wrote:As long as you don't include the vcgt correction in your 3DLUTs you will be fine.
Pacific wrote:Micha Clazing wrote:As long as you don't include the vcgt correction in your 3DLUTs you will be fine.
Thanks Micha - but what is a vcgt correction?
I also saw he's using a decklink card.
I'm on a single monitor setup (NEC PA271W 27" wide gamut monitor) connected via thunderbolt port).
Can you still do an acceptable LUT calibration?
Pacific wrote:Thanks Micha - but what is a vcgt correction?
I also saw he's using a decklink card.
I'm on a single monitor setup (NEC PA271W 27" wide gamut monitor) connected via thunderbolt port).
Can you still do an acceptable LUT calibration?
Pacific wrote:Until I can upgrade my system I have to work with my NEC computer monitor.
Pacific wrote:It's .icc profiles cannot be read by DVR 14.
Pacific wrote:So I found this tutorial that uses Display Cal for a LUT calibration - including the i1Pro probe.
Pacific wrote:Does this work to get a decent calibration?
Pacific wrote:Would the monitor still be able to access .icc profiles when I work with Photoshop and Final Cut Pro X or would those two calibration "fight" each other?
Micha Clazing wrote:Pacific wrote:Thanks Micha - but what is a vcgt correction?
I also saw he's using a decklink card.
I'm on a single monitor setup (NEC PA271W 27" wide gamut monitor) connected via thunderbolt port).
Can you still do an acceptable LUT calibration?
Vcgt means video card gamma table - it's what provides the "calibration" for your monitor in the ICC profile (loaded by DisplayCAL's profile loader). If you include it in your 3DLUT (it's a checkbox in DisplayCAL's 3DLUT maker), the calibration correction will be applied twice, which is incorrect. You could choose to blacklist Resolve in DisplayCAL's profile loader, so that it will unload the gamma LUT whenever you start Resolve, and apply it again once you quit Resolve, but if you alt+tab out of Resolve while it is running, colours in other applications will be incorrect.
Long story short it is the most intuitive to not include the vcgt in any 3DLUTs you make for Resolve.
Because you are not using a Decklink output, you have to set the 3DLUT under the heading "Color Viewer 3DLUT", instead of "Monitoring 3DLUT". Monitoring is for external output through a playout card, color viewer is for the GUI viewers inside Resolve. Make sure to set the LUTs for scopes to "No LUT" or else your scopes will be incorrect.
Using GUI viewers only can still be acceptable depending on your needs - there will be some colour banding because of 8-bit output combined with the gamma 1DLUT. Some members on this forum will stress that you absolutely need to have a playout card and 10-bit output, but I maintain that it is up to your own needs.
Martin Schitter wrote:Pacific wrote:Until I can upgrade my system I have to work with my NEC computer monitor.
in this case, this video tutorial will not be very helpful for you, because it does only explain, how to calibrate external screens, which are connected by a dedicated decklink i/o-card or adapter to your machine. if you want do calibrate the preview on the computer screen, the necessary process looks a little bit different...
(i'm always puzzled by this kind of tutorials, which do not calibrate both kinds of visual representation as good as possible)Pacific wrote:It's .icc profiles cannot be read by DVR 14.
you shouldn't trust into this kind of factory provided monitor profiles. every individual screen will look slightly difernet and will even change its color rendition over time. it's therefor really advisable to calibrate it with adequate measurement devices periodically.Pacific wrote:So I found this tutorial that uses Display Cal for a LUT calibration - including the i1Pro probe.
yes -- DisplayCal and an i1Pro are very affordable tools to handle this kind of tasks in suitable accuracy for more common usage scenarios. for real high end use, you would definitely need much more expensive probes and most likely also utilize other software.Pacific wrote:Does this work to get a decent calibration?
it mainly depends on your monitor whether the results will be acceptable for serious work.
but DisplayCal will present you also very useful validation reports about the actual strengths and weaknesses of your screen resp. it's actual capabilities. that's IMHO just as valuable as the actual calibration benefit.Pacific wrote:Would the monitor still be able to access .icc profiles when I work with Photoshop and Final Cut Pro X or would those two calibration "fight" each other?
this question can be only be answered in two distinctive ways, because output via decklink cards works a little bit different the usual video output via graphic cards on computer screens:
in case of decklink-i/o the answer is quite simple, because this kind of devices are really dumb and are not able handle all of this complex tasks, which nowadays computer graphic cards are able to support. they are only designed, to output simple fullscreen video previews resp. video streams to typical broadcast equipment. they are usually unable to process more complex kinds of color space transformations or compensation profiles. that's a job, which has to be done in the used video application software. but this isn't a significant limitation in practice, because beside this very few specialized video processing solutions, decklink cards are anyway useless. you simply can not use them for work in photshop or any other common software on your computer.
for the other case -- i.e. the preview on computer screens -- the answer is a little bit more complex and can not be explained in a way, which would fit for all different platforms. nevertheless it's a least possible for application developers, that the colors on screen will be always the same! given this very simple premise, it's always possible to compensate the actual visual representation on screen by this LUT preferences provided in resolve in principle -- because it's just a simple transformation between measured data (A) and the expected correct result (B) -- nothing else! but that's unfortunately just a part of the answer, because it doesn't guarantee, that the video preview will indeed look the same in all different parts of the application. that's a very annoying issue, because it makes a lot of sense in practice, to use different drawing and acceleration mechanisms within the same software for different tasks. the cinema viewer and the preview in the edit section and on the color page may handle it in a slightly different way, to archive more suitable results in all of this different work modes. so you would need in fact a whole bunch of different compensation LUTs to compensate all their [possibly] slightly different behavior perfectly. but that's more a kind of nitpicking...
in practice it's really useful to utilize calibration profiles even for the GUI preview. i have to say, it's looks even more important and nearly unavoidable in this particular case, if you want to archive any useful results!
unfortunately BMD doesn't show much interest to improve the computer screen preview capabilities of resolve, because they obviously want to sell decklink hardware devices, which is very understandable interest, but i really have my doubts, if it still fits in our present world resp. the way how most of us like to use computers for creative work.
if they would produce a simple color calibration probe for the same price as a decklink device and force all resove users to make use of this product to get an acceptable full screen preview on one of the attached computer screens, they would perhaps do a better job in advancing the general availability of really useful high quality video tools for everyone.
Pacific wrote:As I'm only using the color page I only have to really look at one particular viewer. So the viewer in the color page would give different colors than e.g. the full screen cinema viewer?
Pacific wrote:My current plan is to ditch .icc profiles and go for hardware LUT calibration of my NEC Multisync PA271 via BasicColor 5. Shouldn't this give me one LUT that would work for all applications from Photoshop to the viewer on the color page in DaVinci Resolve?
Micha Clazing wrote:By using hardware calibration to a Rec709 target you will forego the wide gamut capabilities of your monitor. You can use a hybrid approach where you use the 3DLUT hardware calibration feature of your monitor to calibrate to a theoretical model of your monitor (the listed/measured RGB x/y coordinates and a given gamma curve), and then use DisplayCAL in profiling mode only (so no calibration) to generate an ICC profile with XYZ LUT, and any 3DLUTs you need for Resolve.
To clarify:
Calibration is intended to correct a display's colours to a certain standard (In the case of ICC profiles and 1D LUTs: a certain gamma curve and white point, and in the case of 3DLUTs: a certain gamma curve, white point and gamut). The process for this is to measure a certain colour, measure the deviation from the desired standard, then apply an offset, measure again, etc. until the measurement is within the desired margin of error.
Profiling is intended not to correct a display's colours, but rather to measure what the display performs like after calibration. Any errors that could not be caught by the profiling process are contained within the XYZ LUT that maps the display's RGB colour space as calibrated into device-independent perceptual XYZ space.
So what this hybrid approach does is, instead of either conforming the display to a colour space with a smaller gamut than its native RGB space (like Rec709), which makes it impossible to view for instance Adobe RGB files accurately in Photoshop, or trying to conform the display to a colour space with a larger gamut than its native RGB space (like DCI-P3) which will inherently be imperfect due to the limitations of the display (97% or so coverage of the target gamut), you will be conforming the display to a mathematically ideal model of your display (to the best of its ability). Then you will profile the result of that calibration, and generate 3DLUTs which map standard colour spaces like Rec709 and DCI-P3 to the device native colour space, which you can select in Resolve based on the needs of your project (P3 for theatrical presentations and Rec709 for BluRay/web).
For best results, I would recommend using absolute colorimetric rendering intent when making 3DLUTs for colour spaces with a target gamut that is smaller than your monitor's native space (100% or more gamut coverage), and perceptual appearance for colour spaces with a target gamut that is larger than your monitor's native space (99% or less gamut coverage). Note that any perceptual or relative intent will also shift the white point of the colour space to the native (calibrated) white point of your display. DCI-P3 has a greenish white point (0.314x 0.351y) compared to D65, but this is only an issue if you are trying to match to a projector in the same room. Chromatic adaptation of your eyes will ensure that within 10 to 15 minutes or so, P3-D65 will look more or less identical to DCI-P3. Also keep in mind that P3's gamma of 2.6 is intended for viewing in a pitch black environment. If you grade for P3 in daylight or indoor lighting you will inadvertently raise blacks and deep shadows.
Do note that because your monitor does not cover the entire P3 gamut, the 3DLUT for that colour space will be inherently imperfect. It is always recommended to view your finished product on a real cinema projector as a final quality check to ensure that no obvious mistakes slipped in as a result of imperfect colour reproduction of your grading monitor.
You can safely install the profiling-only ICC profile in your system for use by ICC-aware apps like Photoshop. Because the ICC profile does not contain any calibration data (vcgt), it will not interfere with Resolve.
I'm sorry if I went a bit deep down the rabbit hole, but when it comes to colour management, there are only two modes of operation: either you just blindly follow standard workflows with no understanding of the subject matter, or you have to dive deep and understand exactly what and why you are doing things a certain way. Feel free to ask any additional questions you might have.
Uli Plank wrote:One of the best explanations I've seen in a long time!
Just one thing to add: if you only calibrate a computer screen with a probe, the correction is written into the graphics card. If the connection between computer and monitor is only 8 bit (most of them still are) you may see banding on the monitor and thinks it's a problem with your source, while it not really is.
Serious grading monitors have a USB input and internal circuits with more bit depth to load calibration data, so they'll avoid that problem.
Uli Plank wrote:One of the best explanations I've seen in a long time!
Pacific wrote:What I'm looking for is to create the internal LUT for DVR without affecting the .icc workings of my display. I can't seem to find a step-by-step solution that doesn't include fiddling with the RGB onscreen menu of my monitor which would imbalance the monitor for .icc Photoshop work.
Pacific wrote:I also saw that the color management set by Davinci is Davinci YRGB - which is unmanaged.
Micha Clazing wrote:Okay, first off. DisplayCAL is fundamentally an ICC profiling application. It uses ArgyllCMS, which is a colour management library that creates and manipulates ICC profiles. If you don't want a "traditional ICC oriented" workflow for whatever reason you cook up in your mind, don't use DisplayCAL. Since this thread is about DisplayCAL, I assumed the OP wants to use DisplayCAL. (I don't blame him - it's free!)
Micha Clazing wrote:You can either say "no, I can't grade P3, I don't have the equipment", or you can create a perceptual gamut mapping and go about your business.
Martin Schitter wrote:i really appreciate you description of this more uncommon approach. i just want to see it more as a kind of personal preference and not as the one and only way, how we should all have to handle this kind of tasks in practice.
Florian Höch wrote:Just to clarify, an "ICC" profile is just a file in a specific (standardized) binary format. For the topic of this discussion, this is an implementation detail that has no actual bearing on the discussion.
3D LUT calibration always involves these steps, in this order:
1. (Optional) the monitor may be adjusted to meet certain target characteristics (e.g. whitepoint), by means of monitor controls and/or (also optionally) 1D curve adjustments to each individual R, G, and B channel. You could call this optional step linearization.
2. The monitor is profiled, i.e. its response is measured and recorded, by sending a number of RGB triplets to the monitor. The RGB triplets by themselves have no meaning. The measured CIE tristimulus values are related to the RGB triplets (which adds meaning). We now know "this RGB triplet produces this CIE tristimulus value" on this particular monitor. So, the profile in itself is already a three dimensional lookup table (monitor RGB -> CIE tristimulus), although there is also the possibility to derive simpler 3x3 matrix based models (not as accurate) which we can safely ignore.
3. Now that we have the monitor response in form of a profile (which, in its simplest form, may just be a text file with a list of RGB and measured CIE tristimulus values), we can simulate any other desired response, e.g. by creating a Rec. 709 + gamma x.x RGB to monitor RGB lookup table, that converts between these two responses directly. We could create these lookup tables on-the-fly (how ICC color managed applications work) or "bake" them up-front (which is usually used in the video world).
Andrew Kolakowski wrote:If I have calibrated Rec.709 screen and play P3 video with color management I assume I will get "correct" result (assuming color management reads all flagging and does conversion properly)?
Andrew Kolakowski wrote:If I have Rec.709 2.4 gamma graded video and play it through color managed system and to Rec.709 2.2 gamma based monitor I will get "proper" preview as well? I assume it's not going to be 100% the same as on reference 2.4 gamma based screen, but still should look "correct".
Andrew Kolakowski wrote:More complicated question.
If I have random monitor which can eg. display 90% P3 gamut, but I know its ICC profile perfectly matches its parameters then I should be still able quite reliably grade Rec.709 videos assuming whole thing is color managed. Is this correct? Fact that monitor is not calibrated to Rec.709 should not be a problem at all (as long as monitors really matches its profile and it's above Rec.709 gamut).
--icc-intent=<value>
Specifies the ICC intent used for the color transformation (when
using --icc-profile).
0 perceptual
1 relative colorimetric (default)
2 saturation
3 absolute colorimetric
Andrew Kolakowski wrote:How is the ICC managed? On GPU 32bit float math?
Andrew Kolakowski wrote:If I have Rec.709 2.4 gamma graded video and play it through color managed system and to Rec.709 2.2 gamma calibrated monitor I will get "proper" preview as well?
Micha Clazing wrote: However, since you said your hypothetical video player reads all flagging, the default rendering intent embedded in the ICC profile is perceptual, which means the larger P3 gamut will be shrunk to the Rec709 gamut, resulting in undersaturated colours.
Martin Schitter wrote:but in case of an 8bit connection the visible banding resp. usable color nuances will unfortunately look noticeable worse than on a very simple 8bit rec709/sRGB screen.
Pacific wrote:I just learned that you can convert a .icc profile to a 3D LUT via DisplayCal.
Florian Höch wrote:Martin Schitter wrote:but in case of an 8bit connection the visible banding resp. usable color nuances will unfortunately look noticeable worse than on a very simple 8bit rec709/sRGB screen.
8 bit connections are not necessarily a limitation. A good solution should use dithering to eliminate banding.
Pacific wrote:Cannot create a 3Dlut from the .icc file - displaycal's settings do not show any .icc file and does not let me navigate to it.
Pacific wrote:The 3DLUT maker that comes with DisplayCAL does not open: when I double-click on it in the displaycal folder I get the error message "this application could not be opened"
Florian Höch wrote:Pacific wrote:Cannot create a 3Dlut from the .icc file - displaycal's settings do not show any .icc file and does not let me navigate to it.
Profiles that have not been created by DisplayCAL are not supported by the main application for 3D LUT creation, you'd have to use the stand-alone 3D LUT maker.Pacific wrote:The 3DLUT maker that comes with DisplayCAL does not open: when I double-click on it in the displaycal folder I get the error message "this application could not be opened"
Did you follow the instructions in the documentation (directly under the download link), specifically the bit about removing the "quarantine" flag under macOS?
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