Hi Bart,
Most of the artifacts I see are around high contrast areas, i.e. tree branches and leaves against a bright sky, resulting in various kinds of artifacts. Also around edges of buildings and lamp posts, resulting in a kind of ghostly images many pixels away from the original edges. To me this is so unnatural that it is not usable.
For completeness I need to mention that I’m taking special care not to oversharpen my images.
I only apply GPU processing with my Geforce 1070Ti card. I have zero speed issues.
I fully agree with you that on Jim’s images Gigapixel AI is preferable over the rest.
Regards,
Jaap.