False flattery

[Kaptain Klevtsov]

Quick way to get a false flat is as follows.

Open image in Photoshop.

Create a duplicate layer.

The duplicate layer should already be highlighted in the layers dropdown (f7 in CS2), make sure that the original layer (background) isn't highlighted as you want to leave that alone.

Using the spot healing brush in normal mode click away all the stars. You might need to copy some background over nebulous bits to get the smooth "bright in the middle" signature from the vignetting caused by the optical system.

Use the gaussian blur (filter, blur, gaussian blur) set to get rid of any detail thats left and a bit more.

Invert the duplicate layer (Ctrl I) then set the opacity to 50%.

Flatten the image.

In levels (Ctrl L) set the left hand sliders of each individual channel (Red, green and blue) so that the black point is on the left edge of the histogram.

All done.

Kaptain Klevtsov

[MartinB]

A very handy routine KK and well explained

[barkis]

SAved it in my Docs Folder KK. It will be a great help to me I'm sure.

Thank you.

Ron.

[saturn5]

Brilliant KK, I had read someone used false flats but hadn't a clue how to do it.

[jgs001]

I to have saved it away for future use. Thanks v much.

[cygnusx1]

Just curious KK, how can this flat remove vignetting and other rotation induced artifacts if it is created artificially with no ref to orientation :scratch:

Doh, just reread your post, you use the original image!!