Further testing at home with DVD:
Gaia HQ seems to do the least. Looks like a regular scale with a little detail enhancement. Tool tip says this is really intended for HD sources. (So I’m guessing 1080p to 4K basically.)
Gaia HQ-CG is a mode a lot of people seem to like. I have found that currently, in some sitations, it adds “pattern dither” types of artifacts that are clearly visible even when viewing at a distance on a TV screen. It looks similar to say dithering an image to a 64 or 32 color gif with pattern dithering. I think it’s coming from the training data trying to re-create detail. This effect doesn’t appear in other modes.
The “Artemis” mode is greatly improved. THESE are the settings to use for scaling standard video (480p) to HD (1080p).
Artemis-HQ looks good but sometimes leaves details more blurred than Artemis-MQ. It can also “enhance” certain slightly noisy elements. I think it really needs to be used on only VERY clean sources.
Artemis-MQ seems to be the main setting to use for upscaling DVD and other average to good quality HD sources. It produces the most sharpness in fine details while denoising and removing some other slight artifacts. The file size is only slightly smaller than Artemis-HQ which to me says some denoising is taking place. Film grain is still mostly visible.
Artemis-LQ when used on the same sources begins to start resembling Gaia HQ. Detail is once again lost and many scenes take on a “painter” type of effect. This I believe is due to heavier denoising and deblocking. This mode is inteded for low bitrate sources with visible blocks and artifiacts so it’s mainly trying to remove those. Don’t expect it to save very poor quality VHS or 1990’s “postage stamp” sized video encodes from RealPlayer.
On several discs, including good quality 1970’s films with visible film grain (which you want to keep), and recent 2000’s movies with no visible grain, Artemis-MQ seems to be what wins every time.