Demosaicing and bit dimensions

Started Nov 16, 2013 | Discussions thread
John Sheehy Forum Pro • Posts: 19,800
Re: Demosaicing and bit dimensions

Roland Karlsson wrote:

Mark Scott Abeln wrote:

Ah, I defined oversampling as collecting more pixels at the sensor than the lens can sharply deliver.

Oh, I think you need some more to make it interesting. You really want to be able to apply some digital filtering to improve the quality of the image. Then you need at least 4x more than the lens can deliver I assume. Or maybe it is enough with 2 or 3?

Several years back I did some simulations with blurred B&W edges, box filtering them at various sizes, and upsampling them back to original size and also pixelating them, and it really wasn't until it took 4 pixels inclusive (or 3 exclusive) that luck of alignment had no significant distortive effect on the shape of the edges.  That's my standard; virtual analog.  Anything less is under-sampling, IMO.  I don't believe the common "wisdom" of Nyquist sampling, and reconstruction.  It doesn't work.  It doesn't even work perfectly well for audio, but we get away with it with audio because audio is experienced after the fact and we can not do the auditory equivalent of staring at and studying the waveform, and real-world sounds rarely have perfectly stable pitches, and have some frequency modulation, so artifacts are very short in occurrence.  For imaging, even the slightest distortion is visible, especially with video, as it shimmers with slight camera/subject registration changes.

I know that with current computers and storage media, virtually-analog imaging is somewhat impractical (unless one is using very small apertures, focus is not achieved, or there is circular camera blur), but that is where ideal imaging lies.

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