The Bayer Filter

Thanks for that. Alex Cooke does some really good articles.

Alan

Very good article, he even remembers about Foveon :)

Just minor inaccuracy there - every sampling system (what digital sensor is) needs some kind of antialiasing (AA) filter. For high pixel count sensors lens diffraction itself can be enough to smooth higher spatial frequencies out, also for still image some aliasing is tolerable, makes image crisper. Foveon sensor without AA filter just does not create different color aliasing artifacts, which are most noticeable - otherwise it makes slanted lines aliased as well.

I thought modern sensors did away with the AA filter.

Alan

They say "sensor outresolves the lens" (technically incorrect) - means newer sensors resolution is so high that lens diffraction and other 'blurring' properties/distortions make AA filter basically unnecessary, also microlens and BSI (back-side illuminated sensor) solutions allow to gather light over entire pixel area and this smooths higher frequencies too (lessens some of the aliasing effects).

From an Fstoppers article:

For years the standard defense was an optical low-pass filter, also called an anti-aliasing filter, a thin layer over the sensor that blurs the incoming image by a hair, on the order of a single pixel, to smear out detail too fine to sample cleanly. It trades a little sharpness for protection against moire. As sensor resolution climbed, some manufacturers decided the trade was no longer worth it. Nikon sold two versions of the same body, the D800 with the filter and the D800E with its effect cancelled, and many high-resolution cameras since have dropped it entirely, betting that photosites packed tightly enough make moire rare and the extra bite of detail worth the risk. When it does show up, raw converters include color moire reduction to knock it back, though it cannot always be fixed cleanly.

Fujifilm took a different swing at the same problem. Its X-Trans sensors keep red, green, and blue filters but drop them into a larger, more irregular six-by-six pattern, about 55 percent green, that puts all three colors on every row and column and scatters the repeats. The added randomness is meant to break up the interference that produces moire, which lets Fujifilm leave the anti-aliasing filter off without the same artifact risk. The price is that the unusual layout needs its own demosaicing math, and for years some raw converters rendered X-Trans files softer or mushier than the sensor deserved.

No, everything is reconstructed well. Of course that depends on software - DXO PL8 tended to make thin lines colorful, DXO PL9 is much better in this regard; have not got PL10 me yet. Silkypix is better than DXO - but too slow to do any real work. I don't know about Adobe software - but IIRC Alan uses that and has not complained :)

Adobe s/w works fine on Fuji raw files. As do others now. I've tested Capture One, On1 Raw 2025, ImageForgeRaw, FerrumPix and Affinity - all work OK.