Digital Light & Color

Referring to the thread viewtopic.php?t=4052#p14715

in the AS Noise Reduction tab, unlike the Sharpen tab, there is only the upper roughness limit - I can protect the major edges, but not the high frequency noise from blurring.

Suggestion
Implement the complete frequency control sliders as per the Sharpen tab to the Noise reduction tab.

Rationale
The NR phase will be able to behave as low-pass, band-pass and hi-pass noise reduction

I tried this and unfortunately this does not work as the blurring is based on absolute difference from the central pixel and not on frequency.

The closest I was able to get to achieve this effect was the following:

1) Starting with input image, convert it to monochrome if necessary and then apply a High Pass transformation with some radius that will determine the level of detail to be preserved while the rest of the image is blurred. Apply a brightness curve so that the high pass image is pure white where you want to preserve detail and pure black where you want blurring.

2) Blur the input image or compute the low pass image by subtracting the high pass image from the original using Offset Difference.

3) Blend the original image with the blurred image using the modified high pass image as an Overlay Mask. This lets the high pass details show through the otherwise blurred image.

I tried this on some faces and the results were not especially pleasing, but maybe tweaking the settings could produce a nicer result. Clearly this is an effect you would only want to apply selectively to faces for example.

jsachs wrote: ↑March 16th, 2025, 8:07 am I tried this and unfortunately this does not work as the blurring is based on absolute difference from the central pixel and not on frequency.

Would it be useful to introduce spatial frequency control in the texture mask tool ? Could this control take the form of a grayscale control line ?

I have no idea how to implement this without doing 2-D fourier transforms which are compute intensive.