When I close the Smart Sharpen dialogue box the sharpening effect is reduced.

[helen_elizabeth2002]

With an image open and fit to my screen I open Filter, Smart Sharpen, apply an amount of sharpening, and because I have Preview ticked I can see in the original picture what this looks like. I then click OK to close the dialogue box - but the sharpening applied to the picture when I had the dialogue box open is reduced now I've closed it. In clicking OK to close the dialogue box, I can see the sharpening effect fade in my picture. This happens  both for a smart object or an ordinary layer. 

Could someone please explain? I'm using v21.2.4 on a Mac, but this also happens on the Windows version.

I think that you can see this in the screenshots supplied if you look at the threaded shaft to the left of the dialogue box. I've also included the original unsharpened, in case you think I'm clicking Cancel rather than OK. The latest timestamped file is the original.

[JJMack]

Are you viewing your image zoomed to 100%  while sharping and judging sharpness.  The only time Photoshop displays your actual image is  when zoomed to 100%.   At any other zoom Percentage your viewing a quickly scaled version of your Image Photoshop generated for good performances not best image quality.  At some percentages  Photoshop quick scaling is downright poor.

[Bojan Živković]

@JJMack is probably right, you are not viewing your image at 100% while and after applying sharpening. I can see from your screenshots that actual image is a bit sharper while dialogue is open but that is not proof that sharpening does not work good. Try to display image at 100% then use Smart sharpen. In newer version I am usually using Camera Raw filter for noise removal and sharpening.