Sporgon said:This makes if difficult if you don't know the output size that your image is going to be used at. One of the ways to help here is perform your desired ( small hopefully !) sharpening by converting the image to LAB colour and sharpen in the Lightness channel. When downscaled the artefacts from sharpening are somewhat reduced.
And my point is that the JPEGs I post are sharpened to look good to me at their output size. And then when I post here, they are shown at much larger sizes. If I knew how to post right-sized files for here, the problem wouldn't come up, or at least we could discuss, and maybe disagree about, the sharpening. Just as you say the downsampling reduces the artifacts, so blowing them up here makes them more noticeable. Already sharp white cat whiskers may be a worst case scenario.
I keep my RAW files at full size and don't do any sharpening on them. ACR will do a default "25" sharpening when you open them, but that doesn't affect the actual file, just the XMP, so even that could be dialed back. If I'm going to print, I'll use a different sharpening routine, usually one based on Bruce Fraser's methods. And of course resolution and output size will guide that, just as it does on my JPEGs.