OT nitpick [resolution] [LWN.net]

OT nitpick [resolution]

Posted Sep 2, 2004 16:32 UTC (Thu) by AJWM (subscriber, #15888)
In reply to: OT nitpick [resolution] by guybar
Parent article: Pointless ideology?

On the contrary, if the camera firmware were to do pixel interpolation, it could fake a higher resolution than it actually has. True, a sufficiently intelligent image analysis program might be able to detect this and deduce the real resolution, but I can think of a couple of easy ways to make that difficult. (Eg add a bit of randomness to the interpolated pixels. Add a sharpness transform to the decompression code in the driver. That kind of thing.)

Other than examining the complete driver source code (and maybe not even then), the only real way to be sure is to reverse engineer the hardware, and that's only easy (relatively speaking) if the manufacturer uses standard parts and doesn't conceal the part numbers.

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OT nitpick [resolution]

Posted Sep 3, 2004 12:43 UTC (Fri) by kreutzm (subscriber, #4700) [Link]

Well, what really matters is the resolution the application receives,
isn't it? This is measured routinely for e.g. still cameras using test
pictures. One of those has, e.g., parallel lines with decreasing distance.

So you should be able to ask a photographer near you (or the lab of your favourite computer magazine) to check for it. Either by providing them the camera or borrowing the test picture and providing them the raw (ie. uncompressed) image.

OT nitpick [resolution]

Posted Sep 3, 2004 17:12 UTC (Fri) by ekj (subscriber, #1524) [Link]

You are correct, offcourse, but the thing is, that's not the sort of "resolution" marketed by camera-manufacturers.

My digital Camera is marketed as delivering pictures with a "resolution" of 2500x1800 or something of the sorts, that means simply the numbers of pixels coming out of the camera. There's no way in hell you'd be able to take a picture of a black-white checkerboard with that number of squares on it, and have the individual squares resolve black/white, that picture would appear a fairly uniform grey. (and the fact that the camera outputs lossy jpeg ain't the only reason for that)

My limited, admittedly amateur testing seems to show that the real "resolution" in the sense of "can resolve an object this small" is at most half of the advertised resolution.

OT nitpick [resolution]

Posted Sep 16, 2004 22:24 UTC (Thu) by job (subscriber, #670) [Link]

The pictures that digital cameras take are interpolated. A camera that
advertises 6 Mpixels is 2 M red senors, 2 M green and 2 M blue. (Strictly
not true of course, there are more blue sensors than red I think.) So the
resolution is indeed correct but the colors are all interpolated.
Measuring this in the way you describe is probably pretty difficult.

This is true for all cameras, consumer all the way up to pro. Resolution
may be further damaged by crappy optics, but this is of course less true
the more high end you get. There is one sensors that actually uses a true
3 Mpixels resolution, from a company called Foveon, but as far as I know
only Sigma actually made a camera with that. It turned out to be a hard
sell because of the perceived lower resolution (you know how it is, the
3GHz CPU must be faster than the 2GHz one), so in the end they renamed it
to 9 Mpixels just to go with the lingo.