Hotspot removal

[fwbaumann]

I have thousands of old slides I'm trying to digitize so scanning at 3 min per slide is not an option. Projecting and capturing with a camera is much faster, however, the slide projector gives a hotspot with a light center and darkening corners. I can use a gradient or a picture of "clear" slide (inverted) to overlay the original picture. By adjusting the opacity I can get rid of the dark corners. However, I just want to dodge the center and burn the corners without adding pixels from the overlay. Is there any way of doing this with a mat that just effects levels based on the gradient or overlay picture?

[fwbaumann]

I have thousands of old slides I'm trying to digitize so scanning at 3 min per slide is not an option. Projecting and capturing with a camera is much faster, however, the slide projector gives a hotspot with a light center and darkening corners. I can use a gradient or a picture of "clear" slide (inverted) to overlay the original picture. By adjusting the opacity I can get rid of the dark corners. However, I just want to dodge the center and burn the corners without adding pixels from the overlay. Is there any way of doing this with a mat that just effects levels based on the gradient or overlay picture?

[Sark]

The best way to dodge and burn in PS is as follows.

Add a new layer above your image and fill it with a 50% grey.

Set this layers blend mode to Soft Light.

50% grey has no effect on the underlying image. Black (and dark greys) will burn the underlying image. White (and light greys) will dodge.

What you need to do is use your blank image (clear slide), instead of a 50% grey layer.

Add the blank image above the target image. Set to Soft Light mode, and then group a Brightness adjustment layer above it (Ctrl G).

If you duplicate the target image prior to editing, and have both images open, you can adjust brightness on the edited versions grey layer, until the edited target image compares with the original (minus the hot and cold spots).

An action could automate this for batch processing, but different images may require different settings to the brightness level, so a bit of testing first, is recommended.

Sark