Wednesday, August 31, 2016

Lies Damn Likes and Pixels

Joe sent me a message with this from Microvision's twitter feed last night.

Microvision's PicoP has super high contrast, because black pixels are OFF. There's a lot going on when determining resolution and brightness, not all of which is easily measured.

The picture from PicoP is fantastic -- and the experience is different and better than the numbers describe.

Thanks Joe.

Display Daily   (Much more at the source)

The same is, broadly true of specifications. The simple answer may not give you the messy truth. As we have discussed before in these columns, in some detail, ANSI lumens really don't tell you much at all about how good a projector will look when it's showing a real image, especially an image of the real world in a video or photograph. The ANSI specification doesn't help you understand the issue of colour quality, which is so crucial, and which is why I am persuaded that CLO (Colour Light Output) or measuring output in sRGB are much better ways of specifying projector output. (Is There a New Number for Projector Performance?)

Resolution is Also Tricky

Some of the same issues apply when it comes to resolution. Twenty five years or so ago, I was very involved with high end CRT monitors and these always had a real problem in finding a specification that could genuinely express resolution and performance. Resolution was extremely difficult to define because although those that were not close to the technology thought it was all about the dot pitch of the CRT, the reality was that the actual resolution performance depended also on other factors. These included the shape and size of the CRT beam, the alignment of the three CRT beams and the ability of the amplifiers in the monitor to accurately control the intensity of the beams. In an extreme case, a very fine CRT beam could actually address the left and right hand side of each phosphor dot independently, so there was no coupling at all between the different components that defined the resolution.

The key point about the new definition is that it states that the contrast (Michelson contrast in this case, which helps to avoid issues with displays where pixels can be completely off, such as OLEDs, and which then always show infinite contrast because you are, effectively, dividing by zero) has to be specified at the claimed resolution. "Pass and fail" limits (25% for video and 50% for computer monitors) are still available, but the contrast also has to be shown. That means, effectively, two numbers - the resolution and the contrast at that resolution
The current version will stay at place until a new version of the IDMS is produced. The next full version will further develop the testing to get beyond simple "pass/fail" tests to include colour. Insight Media has published a white paper, written by Michael Becker at Display Metrology & Systems (DM&S) in Germany, explaining these changes and which can be downloaded here (registration required).

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