Just spotted that the Mac app Super Denoising is a free download at the time of writing.
Gave it a quick trial on one of the noisy microscope photos:
I had already tried 'denoising' the original in Serif Affinity and my old version of Photoshop Elements and that was the best I could achieve. So far on this quick test I am very impressed with Super Denoising. Although the results may not perfectly match what was originally seen by eye as it is liable to lose some small detail it certainly makes a good attempt at cleaning things up.
1 hour ago