Alan Smithee asks …
I open my photo, a scan, add an adjustment layer for levels, one for contrast, then one for "dust". I then try to make a layer for Sharpening but it seems to have no effect. What am I doing wrong?
You need to sharpen on the bottom layer with the actual image data, not an adjustment layer or on a new blank layer on top of the layer stack.
I notice that if I just open my photo THEN add a layer for sharpening it seems to work (most of the time) but I don’t understand why it doesn’t work the other way
My guess is that you still have an adjustment layer selected and are sharpening on that instead of actual data (I’ve done this a hundred times myself).
Here’s a tip for you to get around all this … add your adjustment layers and make all your changes to them, then select the highest layer in the stack and make a new blank layer, which should come in on top of the stack. Now hold down the Alt key (Windows) and while holding it down do Layer > Merge Visible … it won’t actually merge all the layers if you hold down Alt but instead will make a composite layer at the top of the stack, with all the data in the layers below.
Now run USM on this composite layer … I usually name it after USM with the parameters, something like ‘USM 200 2.2 0’ for 200 amount, 2.2 radius, 0 threshold (as an example). Now you can turn this layer off and make other composites and run various USM values, and you also haven’t touched the base layer data while leaving the adjustment layers intact for future editing also.
Bill