Did a quick read through, a couple things I would change:
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The target value for average gamma we are trying to achieve for our display is 2.2. The ColorHCFR software tries to target 2.2. The ideal target is to match a properly calibrated (telecine) mastering reference monitor used by the movie studios. These monitors are designed for a ruler flat 2.20 response.
Target gamma is actually inherently assumed 2.5, which is inherent to a CRT and thus the reference. The encode gamma from NTSC days is 1/2.2, which is where the 2.2 comes from(which is an incorrect interpretation since that defines the encode, NOT the assumed de-gamma), which is a very commonly assumed target which is not actually correct. The flow is actually not linear, and ends up about 1.25 for better subjective viewing results. It is unfortunate that this software and others uses 2.2 as the target. Even accupel does the same, despite the fact that in their white papers they are quite clear that 2.5 is actually the desired display standard gamma. Lower gammas can be preferred for subjective reasons, but are not standard.
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You'll need a test disc with 0 to 100 IRE window patterns. We recommend the Digital Video Essentials: HD Basics disc (in either Blu-ray or HD DVD) as it's the most up to date and the least expensive. We do not recommend using the Avia DVD as the greyscale patterns are incorrect! (The authors have admitted to this).
I would though, include Avia II which is correct, and is a handy disc to use. I recommend it. Additionally, I strongly dislike using the IRE units at all, and would prefer % be used instead as IRE units are very confusing, and not really correct to use anyway. Although, Avia II still uses the asinine IRE labels and is based around 7.5IRE setup, which makes it very confusing. So actually, maybe I take that back, using DVE which is labeled in % is more clear for greyscale. I prefer Avia II for many other settings, and usability though.
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Note: The 4% below black (blacker-than-black) bar may not be visible on your setup. That's fine and normal. Don't worry about it. Not all setups will display blacker-than-black (or whiter-than-white) content. You aren't losing out on anything if you cannot see this content.
That's not normal, nor "fine." It may not be a big deal, but such a system is clipping the video range. It deviates from reference performance and is not preferred, and can have impacts on the image. That may not be significant for some viewers, but that doesn't make it "fine" or "normal."
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If the blue and green primaries on your digital projector are too far out causing the colours to be too vibrant, you can possibly tame them a bit by adding a neutral density (ND) filter in front of your lens. The CC20R, CC30R, and CC40R filters (for example) are popular choices. These are light filters that can be added into the light path in front of your digital projector. It limits the light output which can help with the black level and also has the effect of pulling in the blue and green primary points (red remains unaffected). The number represents the percentage of attenuation that is performed, so for example, a CC20R filter attenuates light output by 20%.
Slight confusion, those are not neutral density filters. A neutral density filter is by definition neutral, and will only reduce the light output. It will have no effect on color, or any other projector settings whatsoever. All it will do will dim the light output. The filters listed are not neutral, thus they will affect greyscale balance across the entire spectrum evenly. Obviously you'll want to use the right filter for the right purpose.
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Since the filter reduces the bulb light output at low light levels, the color correcting filter gives you the added bonus of deeper blacks and improved contrast ratio.
The filter itself is passive, and will hace no inherent impact on contrast ratios, regardless of whether it's a colored filter or a neutral density filter(and the ND filter will not have any at all). The reason to use a color filter on a digital display is that often a digital display will have too much blue or green, but using the gains in the digital projector to pull those in can have the effect of reducing the contrast ratio since you have a limited on/off CR range for each primary, essentially. As you essentially lower the gain of each primary control, you also will have to lower the global white level setting to stay below the display's white level clip point as the primary gains are lowered. This sacrifices contrast ratio. Using a colored filter achieves this without needing to sacrifice CR at all, or as much since you may not need to adjust down the primary gains at all or as much in order to achieve good greyscale. In this manner, a colored filter can have the end effect of improving your
calibrated contrast ratio, but it in and of itself will not affect CR at all, except insofar as it helps during the calibration process.
Additionally, it may be worth including a note as to the distinction between D65 and 6500K. They are not really the same thing. You describe 6500K as a neutral color early on in the guide, then switch to D65 terminology later on. D65 is the standard, though 6500K is very close to it. Not that big a deal for the novice, but that should be clearer.
Hope that helps tweak the guide a bit, and thank you so much for writing up such a useful guide Kal!
