However, a JPEG image posted on the web can appear overly-sharpened when you really didn't do it during processing it as a TIFF. Why? Simply because the JPEG algorithm "compresses" faint features during the process.
I'm going to post some screenshots below from Photoshop. However, just saving the screenshot will itself be a JPEG and some of the finer details may be re-compressed.
Here is very frilly prom (Hydrogen-alpha) that I posted as a JPEG on a forum in 2018... Looks "okay", but compare it with this one that has had the compression removed.. Even looking at the two thumbnails, it is obvious that the second one is much smoother, and better represents what the prom really looked like when shot.
(In my layer stack, the second (red) layer removed the artifacts and turning it on/off was all I did to make the screenshot. Note the "eyeball".)
Perhaps to a lesser degree JPEG compression can even affect a white-light image. Here's a very nice WL image of AR2781 shot by Mark, aka "Thefatkitty" last week... Thanks Mark! Compression on... Take note in particular the white spots in the penumbra surrounding the black area (numbra) of the spot itself and compare them with the same ones when the compression is off...
So, how do we fix it? After all, sharpening is a part of this game. The short answer is... We can't. JPEG images are just a fact-of-life when posting on the web.
We can, however, negate much of the effect before we save our work for the web... sort of.
First off, dull your sharpening pencil. By that, I simply mean to be judicious when sharpening in the first place. That sounds easy and it is. Our next step will help you sneak up on the amount of sharpening that you can "get away with".
Photoshop, and others, allows one work away processing via a stack of layers, each one being an additional edit. What many don't know is that
Before I flatten my working stack to save it for a JPEG, I save the entire stack as a PSD file. That way I can flatten and save as a JPEG to see how much I lost via the compression. If it is too much, it is a simple matter to open the PSD file for adjustment before doing the whole JPEG compression thing again. It may seem tedious, but it is really very simple once you become accustomed to it.
If you got this far, I thank you for your patience and solicit your comments below.
Clear Skies & Stay Safe