Understanding 4K Resolution in Projection Systems

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Offline DCI forum

Understanding 4K Resolution in Projection Systems
Understanding 4K Resolution in Projection Systems
« on: Wed May 31, 2017, 12:32:36 PM »
Here is a nice article regarding 4k projection by Chris Chinnock, Insight Media.

You might be surprised with their findings.

See attachment for the PDF.

Linkback: http://dci-forum.com/d-cinema-hi-end-cinema-home/11/understanding-4k-resolution-projection-systems/2066/

Offline donaldk

Understanding 4K Resolution in Projection Systems
Re: Understanding 4K Resolution in Projection Systems
« Reply #1 on: Thu June 08, 2017, 10:53:21 AM »
Chris is not the first to arrive at the conclusion that we need to test and measure for the Contrast at a given resolution, or the other way round the resolution is that frequency/number of pixels/lines that can be displayed with a given level of contrast. And color resolution and so on.
Luminance contrast can be dependent on colour contrast, hence Florian Friedrich CEO of the German test laboratory, AVTOP (that also developed the HDFury HDR control software) argument against colour subpixel subsampling a few years ago.

ICDM turned this into a standard as Bob Raikes that took over as editor/publisher at DisplayDaily from Chris Chinnock, points out.

At the time, and after a lot of thought, I came to the conclusion that the only way to really specify the resolution was to quote the resolution and also the contrast between adjacent pixels at that resolution (which I called detail contrast). The idea was that monitor buyers would then be able to decide what level of detail contrast was needed for a particular application and set their 'cut off' for tenders and RFQs at that level. That would have really helped me to communicate the superior quality of my products to customers without having to get into side by side demonstrations (which we invariably won, in terms of image quality, but which took a lot of time).

Unfortunately, in those days, I was a "sharp end" in sales and marketing and really didn't understand the way that the display metrology community and supply chain worked, so I wasn't able to change things at all.

The controversy on "what is resolution" may have now been resolved (pun intended) by a decision by the ICDM in May to adopt a modified method for defining resolution in the current IDMS standard for display measurement, as the previous version had been created with only RGB pixels in mind.

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.

Candice H. Brown Elliot delves deeper into the issue and new standard.

The standard document with the various updates/errata documenst can be downloaded here.
« Last Edit: Thu June 08, 2017, 10:59:14 AM by donaldk »