Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul D. DeRocco" 
<pderocco@i...> wrote:
> Does anyone here know of a Photoshop plug-in that simplifies compensating
> for lens vignetting? I've managed to do this with a circular gradient, but
> boy is it a pain in the butt. I can imagine how one might work: a curve
> editor that lets you specify the amount of lightening as a function of the
> distance from the center of the picture, while previewing the result in real
> time. Seems like an obvious thing to want, so I'm hoping it exists.
> 
> --
> 
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@i...

Paul,

You can pretty much do this with Photoshop.  
Along the lines it sounds like you've already started:

Do an Adj Curves Layer to lighten the corners.
Then add a circular grad as the mask -- black to white, center to corner.
Now you have the center un-lightened and the corners 100% lightened
and the gradient is linear from center to corner.
Now use Adj Curves on the gradient itself (I don't think there's any
way to make the gradient adjustment another layer).
In the adjust curves the input side is basically the distance from the
center and the output is the amount of lightening.  So work the curve
so the beginning of lightening happens where you want it.
This Adjustment isn't a layer so you don't have quite the flexibility,
but you can Undo and try again with <opt><cmd>M.   This returns
you to exactly the same curve so you can iteratively work on it.

Roy