Am 06.11.2017 um 10:50 schrieb cbpypov:

> However, the dithering works great, as you suggested. BUT, only if PNG output
> format is used (JPEG stays almost unchanged!), and only using the
> Floyd-Steinberg. The Bayer dithering even increases the problem! Unfortunately,
> the Floyd-version increases the PNG file size to 1.2 MB per frame in Full HD. So
> it will be quite large if I render 5 minutes at 30 frames/s ;) But I'm fine with
> it...

Well, without dithering you do have less entropy in the image, so it can
be compressed more strongly without loss.

As for not giving an advantage with JPEG, that's intentional: Dithering
is high-frequency low-amplitude noise, which is exactly the type of
signal JPEG compression tends to throw away. With POV-Ray's standard
JPEG quality settings you wouldn't see a difference between an image
that had dithering applied and an image that didn't. You'd need
top-quality settings, at which image size probably wouldn't differ much
from a PNG. Therefore, JPEG output currently doesn't support dithering
at all (though I might change that).

Please elaborate why you say the Bayer dithering "increases" the
problem. In my own experiments I do still see concentric artifacts (*),
but IMO they're less obvious than without dithering.


(*) My guess is that this is due to gamma issues. I knew this could
theoretically be a problem, but I never thought it would be noticeable
at 8 bits per colour channel. I did already work around this issue for
the dithering algorithms based on error diffusion (such as
Floyd-Steinberg) because it was comparatively easy to solve there, but I
guess it would be quite difficult to adapt a purely pattern-based
algorithm (such as Bayer) to be equally "gamma-neutral" (except for the
special case where output is 1 bit per colour channel).

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