Watercolor

[Marpel]

I have an image (6000 x 4000) that contains no photographic components, and was fabricated as follows:

Generated two new 48 bit colour images, each of which is a solid colour (orange and bluish).
Generated a gradient mask that is the vertical default, so is a smooth black to white from top to bottom.
Composited the two colour images, using the noted mask, with the result a blue to orange gradated image.
Using that image as a background, I added a number of other elements to the image.

I then ran the final image through Watercolour, with the settings left at their default positions.

The resultant 2000 pixel image has a great number of very noticeable horizontal dark lines evenly spaced across the entire background of the image. Because the lines are so evenly spaced from top to bottom, I suspect they are related to the quality of the gradation mask(banding maybe??). The original image shows no lines or banding at all, regardless of zoom level and if converted to 24 bit, the lines are still invisible to the eye.

Trying to eliminate the lines, I tried a number of variations of the Watercolour settings with limited success. The best I could accomplish was by using a quite high sharpening amount, but that added significant colour blooming between the elements in the image and the background.

Any suggestion on how to eliminate/prevent these lines and any idea why they occur?

Thanks,

Marv

[jsachs]

This kind of banding is normal for this transformation and results from repeated application of the median transformation.

[Marpel]

Thanks for the answer, Jonathan.

Regards,

Marv