Re: Polarizer Problem In article <1148644956.769945.75400@g10g2000cwb.googlegroups.com>, stefan.
fischer@cyberfun.de says...
Stefan,
What you are seeing is vignetting at the lens outer edge. If your sensor was
circular, and the resulting image was circular, you would see a dark circle (
soft edged) around the entire image.
If you shoot in RAW format, and Adobe Camera Raw plug-in supports your camera,
you can minimize this vignetting in the settings - second tab, and under "
Vignetting" IIRC.
If you have not shot RAW, then the best thing to do is create a Radial
Gradient Layer Mask. This will be a bit of trial-n-error, to get the radius
and the degree of transparency to black correct, but once you have created it,
you can Save this Alpha Channel for use on other images done with the
Polarizer. Open one of the images with noticible vignetting. Hit Q (for Quick
Mask Mode), Open the Gradient Tool, and set the Options box to Radial, then
Black to Transparent. Experiment with dragging the Gradient Tool from a corner
to the center of the image, moving your mid-point on the Gradient Tool to try
and match the vignetting. Once you have gotten it very close, hit Q again and
you will have an active Selection, which you will Save (Selection). Now you
can use that Selection for an Adjustment Layer. I'd start with Levels, or
Curves, knowing that an Adjustment Layer for Color Balance, and/or Hue/
Brightness/Saturation might also be needed. Explore the Adjustment Layer
settings to match the edges of your image to the center.
Another way would be to hit Q, create a circle (Ellipse Tool, Alt/Shift to
draw from center/constrain circle), then Fill, Ctrl-Alt-I to Invert), then
experiment with Gaussian Blur on the edges of the circle. I think Gradient
Tool is a better starting point, but that's just me.
You might want to look into a larger Polarizer and necessary step-up ring, but
are likely to still get some vignetting just from the Polarizing effect.
Hunt
Noone@hunt.com (Hunt)
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