Tom, here is my procedure for changing skys. It works really well eliminating fringing etc.

Select sky – select – color range
Click in the sky area – drag fuzziness to about 133 to get nice tight selection of sky – OK
On channels palette – click on save selection as channel icon
If the sky is white in the alpha1 channel – press ctl D to deselect – double click on alpha1 channel title area and then choose color indicates selected area – OK
Now clean up the alpha1 channel – click on alpha1 channel to move your view to this channel -–zoom in to 100%
Now using eraser tool erase some of the black areas beneath the treetops
Open new sky photo and crop to correct size and resolution
With new sky in foreground drag its title from layers palette into the photo. This makes a new layer with the sky.
Press 5 on the keyboard (KB) to reduce opacity of sky layer to 50% - now you can see both layers
With the move tool position sky
Press 0 on the KB to restore sky layer opacity to 100%
On the channels palette click on load channel as selection icon at bottom of palette
Choose select – modify – expand – type 2 in pixels field, then OK. What you’re doing here is expanding the saved selection ever so slightly so that new sky trims away the hazy blue fringing around treetops on the background layer.
Choose – select – feather – 1 pixel – OK
Choose select – inverse and then with sky layer selected press DELETE key
Ctl D to deselect.


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Bert D
http://www.pbase.com/robgiraffe/art