clipka <ano### [at] anonymousorg> wrote:
> >
> > How can I avoid these rings? Normally (e.g. in Photoshop), I'd just add some
> > **Gaussian noise** to blur the interfaces of the color values (which is there
>
> Actualy, Photoshop's gaussian blur filter wouldn't help you here: This
> is colour banding from colour quantization.
>
> What you really need is dithering.

I wrote **Gaussian noise** (see above), not _blur_ ... and from what Wikipedia
says about dithering:

    "Dither is an intentionally applied form of noise used to randomize
    quantization error, preventing large-scale patterns such as color
    banding in images.",

it seems to be almost exactly that ;) Somehow I had not stumbled upon when
dithering is used before, but I am not easily fooled when it comes to Photoshop
:) If you apply Gaussian noise -> Color noise reduction -> Gaussian blur (in
this order) even the Jpeg looks good.

>
> As of v3.7, POV-Ray provides inbuilt dithering via the `+th`
> command-line switch. By default this enables Floyd-Steinberg dithering,
> but alternatives are also available. Most notably, `+thB4` activates 4x4
> Bayer dithering, which may (*) be a better choice for animations.
>

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...

Thank you very much :)

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