Resolution falls off gradually until it is no longer measurable or noticeable. Think of a gentle ramp on an X-Y grid, starting at 100 and gradually lowing until it reaches zero. That is what happens to your resolution when you photograph. The lens has fall-off, the image sensor or film has fall-off, image compression may have fall-off, the display device has fall-off and don’t forget the human watching the image. Glasses aren’t perfect and we know humans have much worse eyesight than the animal kingdom.
Where does that put us? If an image sensor is down 75% at 4k, the lens is down 60% at 4k and the display device is down 80% at 4k, what are we actually seeing out of a 4k image train? The answer is not much.
Try to get MTF (modulation transfer function) curves from lens manufacturers. They don’t like to give that info out because it makes their lenses look so bad. And what is the depth of modulation for the RED camera at 4k? That info is not published on their web site.
If we add all this together, we find we sample very little at 4k. But it doesn’t matter much.
As you know, the Sony Cine Alta camera does not record full HD. Instead of 1920 pixels horizontally, it records only 1440. Sort of 1.5k. When first introduced, it was compared with film and all the demos looked great.
The resolution under 2k is more important than the resolution above 2k.
With better lenses and higher definition cameras, the images are constantly improving. If a camera can sample 4k, it looks great at 2k, much better than a 2k camera. If the Cine Alta can sample 1.5k, it looks much better at SD resolutions than an SD camera that samples only .5k.
Of course the next step is an 8k camera followed by a 16k. And you can hear the marketing gurus tell you that finally we have 16k, which is what you really needed all along.
Don’t laugh too much. NHK as a prototype 16k system called “Ultra Definition” with 22 channel audio.
Remember the next time you drop in that Pro Mist filter for a close-up, you may be only getting 1k resolution. But in that case, that is enough.
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