Even illumination of flat image, removing shadows.

You have two separate problems here:

• The central hotspot is overexposed and washed out
• The corners are underexposed

So in principle, two adjustment layers to tackle each problem:

In this case, however, the vignetting is really extreme. So you'll have to rinse and repeat. Expect a lot of grain in the corners, and some severe shadow color casts that need correcting too.

See how the light source is on the face of the subject but the surrounding is dark.

Hi please show us picture so we can guide you properly that is not difficult....Thanks.

Hi

Depending how much difference there is in the illumination, you may be able to use curves with gradients on the mask. Do you have an example that you can post here?

Dave