Creating a Realistic Rainbow

[Shotster]

I'm stuck on a problem that I thoguht I could use hidden power tools to solve. I need to create a realistic looking rainbow. I actually have a rainbow partial image from a digital cam, but I've tried saturation masking and blend masking to try to "isolate" the rainbow no avail.

Anyone have any suggestions for how to go about creating a rainbow either from scratch or by using part of an existing rainbow image?

Thanks for any help.

---
Steve

[pmarchant]

Is there a distinctive edge with your existing rainbow? If yes, on a duplicate layer use the background eraser to remove the "red" and "violet" parts of the rainbow. You can then easily delete the inner part of the rainbow. You might want to make this layer the only visible layer so that you can see the rainbow disappearing. Once you've deleted the rainbow you can then use this layer as an alpha to extract the rainbow:
1. remove the visibility of the alpha layer
2. duplicate the original layer and make sure it is visible and active
3. Ctrl-click the "alpha" to select everything except the rainbow
4. press delete, then ctrl-D to deselect.
You've now got a layer with just the rainbow.

Or if you want to use the hiddenpower tools:
1. make the original layer visible.
2. set the blend mode of the "alpha" layer to "difference"
3. flatten the image (or create a flattened layer)
4. use the HP tools "Clear Black" followed by "Commit Transparency"

Cheers,
Paul