Originally Posted by Fudoh
This would imply that gamma and greyscale should be set with checkerboard patterns instead of plain grey fields, right ?
The reason the gamma charts use both a dither of black and white and a grey is that black and white stay the same during gamma adjusting, and the dither pattern blends optically in the eye when seen from enough distance to make a grey reference. The actual grey, the solid areas is what changes when the gamma curve is adjusted. It's a clever test pattern for setting up gamma quick and dirty without a luminance gauge.
The first one with lines going different ways and with checkerboard too serves not only as a quick gamma check, but also as a test for ringing/soften/sharpen type distortions. If a screen is setup perfectly, then that pattern would appear as nothing but a big grey rectangle from a distance, with the exception of the white and black bars in the middle.
Such are only recommended to be used at native resolution for adjustments, because the interpolation during scaling tends to distort the dithered parts, which is what I demonstrated, and was wondering how the Duo does interpolation, whether it would take, for instance, a pixel of 100% luminance (255 rgb), and another of 0% (0 rbg), and arrive at 50% (185 rgb) between them, or if it would do linear interpolation on the digital rbg values and arrive, incorrectly, at an rbg value of 127 (22% luminance) for the same pixel, as very, very many scaling algorithms would. Not because I want to use upscaled gamma patterns for any adjustments, but simply because I'd prefer it if when deriving the intermediate color between pixels, that the scaler would do it based on the actual luminance line between the pixels, the way light actually blends in the real world, not the digital color value, which is logarithmically (base 2.2 normally) proportional to luminance, not linear.
I know I'm rather picky, but these things aren't cheap enough for me to buy lots and just use whichever I like best, so I'd like to find out the peculiarities of them before buying stuff that (usually) can't be refunded.
With scalers that don't interpolate, none of this matters, but I didn't even realize there were any that didn't interpolate (such as the X-RGBs and several others from the looks of the screenshots.)
This is starting to get OT from the iScan Duo now though...