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p.1 #1 · p.1 #1 · Questions about pixel density and viewing distance... | |
First, I'm not sure if this is the best forum to pose this topic. Apologies in advance if it isn't.
I'm in the process of defining a Home Theater system for my condo in a small 13' x 13' x 9' downstairs finished room. I anticipate viewing my video monitor from 7' to 9' away. The audio description of my proposed system is separate from this topic. I anticipate having many digitized "slide shows" on my TV monitor (TBD).
In general, I believe that most agree that we get enough resolution from 4-6mp digital image files to equal usable detail which existed in 35mm film. Obviously, we can do much better than that today with 35mm format vDSLRs (Nikon = 36mp, Canon = 50mp). Even more resolution is on the way. But I digress.
A few 4K video questions to ponder. First, how well will it render digital still images? (Slide shows are at least one useful application.) Obviously, viewing distance matters. I'll come to that later. (How accurate is the chart below?)
Consider the native 4K resolution: 3840 x 2160 pixels in a 16:9 aspect ratio. If we truncate the horizontal resolution to 3240 pixels (to accommodate the standard 3:2 aspect ratio for still images) we arrive at approximately 7mp of image data (3240 x 2160). Note that 1080p resolution when scaled to a 3:2 aspect ratio only produces about 1.75mp of image data. A huge difference and far less data that is required to effectively render 35mm still images.
For those mathematically inclined, lets take a look at PPI (pixel-per-inch) resolution and monitor size. Let's first arbitrarily assume 72 PPI is a desired goal. (Question: how will a viewing distance of approximately 8' affect the arbitrary 72 PPI goal?) And what is the minimum monitor size needed to achieve this? (That's the somewhat incomplete exercise which follows.)
If we work from this arbitrary starting point, we have (3240/72) which yields 45" for the horizontal dimension. The 3:2 aspect ratio then gives us 30" for the vertical dimension. Using the Pythagorean theorem yields approximately 54" for the diagonal dimension. That dovetails nicely with the 55" sweet spot for TV monitors today. However, that omits the necessary re-scaling back to the 16:9 aspect ratio, since TV sets/monitors do not render in 3:2 format.
So, using 30" as a fixed vertical dimension and re-scaling the horizontal (longer) dimension back to the 16:9 aspect ratio, we get dimensions of 30" x 53". From this, again using the Pythagorean theorem we derive a diagonal dimension of about 61". So, does it then follow that in order to effectively display "35mm digital images" that a 4K monitor should minimally be a 60" or 65" unit? (Assuming the above parameters.)
All things being equal I know that color gamut and contrast trump resolution, but resolution and viewing distance DO matter. So, another question to ponder: How does a viewing distance of approximately 8' factor into all of the above? Any opinions? (I know, this can dovetail into broader topics.)
Thanks in advance for your critical thinking!
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