How do you correct vignetting digitally ?

[QT Luong]

I recently had to prepare a color image for which the vignetting was massive: 90mm on
5x7, lots of uniform areas of sky and water. At that time, I didn't have a CF filter. Curiously, it was quite noticeable on the transparency, but not that bothersome. However, in the scan, it really looked bad. I tried to apply a radial gradient in PS, and it did fix the luminosity, however the edges and
corners took a visible saturation loss that was unacceptable. Do you know a way to combat that problem ? Or is there a plug-in which works ?

[Ron Marshall]

I don't know if this will help, it may be what you have already tried, but in case it is of some help: http://www.luminous-landscape.com/tutorials/panorami.shtml

[chris jordan]

QT, try doing the adjustment as a layer in Photoshop, with a radial gradient (as you already dide), but put the layer in Luminosity mode instead of Normal mode. That way the color won't be washed out by the brightening. Then if the color is still problematic, you can use the same gradient mask in another layer to bring the color back further-- either a Hue-Sat layer or a Selective Color layer.

[Henry Ambrose]

You're in for a tough go here! Not seeing it myself I'm guessing/thinking outloud that one or more of the following might help you:

Try "selective color" to tweak the affected parts to look more like the good parts.

Saturation dodge and burn tool used locally - its gonna happen best a little at a time. Save this for last when you are fine tuning.

If its still in layers go back to your radial gradient and load that on another layer and tweak the blending? Perhaps try a "screen" blend that has the center gradient "knocked out" of it.

One more thing might be layering another scan adjusted to correct the bad color (boost the saturation in your scanning software). Layer the good outer zone scan on the good innner zone scan.

Give up on perfection and try to get it "acceptable" and maybe you'll luck out and overshoot your goal - I tell myself "OK - its not gonna be perfect but I'm going to make it really, really good." That usually works for me.

Good luck to you!

[Frank Petronio]

I get lost using cookbook recipes and channel chops - I always forget how I did them and can't repeat them.

What I do is simply copy the image onto another layer and make a Levels adjustment to get the dark corner to where I wish it would be. Then I take a large, soft edged brush and my Wacom stylus and erase away the unwanted areas on the second layer. Just dab away until they match to your eye, leaving some slight imperfection so it isn't too perfect.

Or take a snapshot and paint it in with the History brush, or ... but the idea is to use a Wacom and do it by hand, not by mathamatics.

The other thing you can do is paint the sky blue back in with the Paintbrush set to "Color" and sample the blue color. Paint over the desaturated or mucky areas that have the right luminosity, and feather it in (don't go sploshing 100% with a hard edge brush.)

I do that all the time to rescue mixed color sources in architectural and industrial shots.

The problem with blue skies is (and this is much worse in CMYK Litho) is that the color is made up of lots of Cyan and a little Magenta (in ink, that is). As the sky's blue feathers off, the percentage of Magenta lowers quicker than the Cyan, eventually reaching a point where the Maganeta is 0% while the Cyan is still at 5% or so (not counting other colors, etc.). This forms a harsh line in the transistion, and ruins a lot of prints. The answer is to randomize, introduce noise (using the snapshot and History brush), and doing other things to muck up the mechanical precsion of that perfect gradiant.

[Lars Åke Vinberg]

Sometimes I run out of image circle without noticing. so the corners get clipped a bit. If it is a clear sky or fuzzy clouds then it is possible to stretch the image a bit using the Smudge tool.

[Paul Cutler]

I use the radial density filter made by power retouche for exactly this issue and it works well each time. Basically it does what the photoshop tools do but through one simple interface. It can lighten edges or darken the centre. It may be worth a look.
Link is: http://powerretouche.com/Density_plugin_introduction.htm

[Ted Harris]

I find that careful use of the clone tool often works too.

[Graeme Hird]

I'm probably too late to help much, but when it happens to me I usually crop as much of the problem area out as possible. Some slight corrections may be left to restore, but they are often minor and usually less noticable than if I hadn't cropped.