Posted on June 11, 2018 By Nikki Zelinger
ViewSonic PX727-4K Projector Review – Advanced Calibration: CMS Calibration, Calibration Charts
User 1 Mode Pre-Calibration CIE 1976 Saturation Sweeps (target REC 709)
User 1 Mode Post-Calibration CIE 1976 Saturation Sweeps (target REC 709)
The default CMS looked to be hand adjusted at the factory because the values for all six colors were not at their centered (default) positions. A common color gamut issue I see with the PX727 and other current generation of 4K/DLP projectors is the over saturation of mid-level (i.e. 20%, 40%, 60%, 80%) color points. The before color gamut chart clearly shows this problem with red, green, blue and magenta. For example, take a look at red’s 80% color point sitting over at the 100% target along with the 100% point. What this means is 80% red saturation looks the same as 100% saturation, and 60% saturation actually measures close to 80% and so on down the line. In addition to these saturation level errors the hue of cyan is problematic with 100% saturation taking a turn north towards green.
With calibration all of these errors were reduced in some manner, some more successful than others. The over saturation problem was reduced but not eliminated and the hue issue with cyan can’t be fixed only massaged for a slightly better compromise.
Standard Mode Pre-Calibration CIE 1976 Saturation Sweeps (target REC 709)
Standard Mode Post-Calibration CIE 1976 Saturation Sweeps (target REC 709)
CMS in Standard mode exhibited similar errors to User 1 but to a lessor degree and the 100% cyan hue error was pretty much eliminated. Although 100% white was a little bit green (minus blue) all of the colors calibrated very well with their mid saturation points coming in closer to their targets than my Best/Dark Room calibration.
User 2 Mode (4K/HDR) Pre-Calibration CIE 1976 Saturation Sweeps (target REC 709)
User 2 Mode (4K/HDR) Post-Calibration CIE 1976 Saturation Sweeps (target REC 709)
ViewSonic states that the PX727 is a REC.709 projector with REC.2020 compatibility. So, when you feed the projector a 4K/HDR/P3 signal it will down convert the P3 color gamut to REC.709. Pre-calibration color gamut looked like it had been pushed quite hard with the mid-level (i.e. 20%, 40%, 60%, 80%) color points over saturated quite a bit. Worse than I saw with 1080p/SDR. Cyan’s 100% saturation point error that I got with my Best/Dark Room calibration is also seen here. Calibration did however help quit a bit pulling those mid-levels much closer to their targets. Cyan and yellow hue errors could not be eliminated and still retained some green tint to them in their 80-100% saturation levels.
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