Hello,

First time poster here.

Just curious about how to change sky-colors like you see in a lot of professional photographs. For example, on this site:

http://www.novascotiaphotos.com/

...the banner at the top has purple sky, and there are several photos in the gallery with different sky-colors. What's the best way to go about doing this using the GIMP? I've been doing some googling, but I'm probably using incorrect search terms since I haven't really found anything helpful (yet).

Any replies are appreciated!

Regards, Joel

Il giorno ven, 14/11/2008 alle 19.09 -0400, Joel Glanfield ha scritto:

Hello,

First time poster here.

Just curious about how to change sky-colors like you see in a lot of professional photographs. For example, on this site:

as already someone replied, at sunset and sunrise the sky colors are wonderful. You might achieve nice results also by using a polarizer (if you can attach it to your camera): it really makes the difference

If you want to artificially change the colors, I think the best way to do it, is to do it in a selective manner:

1) duplicate the layer of the original photo 2) change the color of the duplicate layer by using the color balance tool to reach the sky tonality you want (don't pay attention to want happens to the rest of the photo)
3) apply a layer mask to the modified layer (hiding all the modified layer)
4) select a brush with proper dimensions and draw with it over the layer mask: this will reveal the modified layer. If you draw only over the sky region, you will obtain the sky with your colors, while keeping the rest of the image with original colors. You can play with different brushes and different brush settings (I found the opacity setting very useful) and see how to get the best results

Hope this helps

Marco

Marco Presi writes:

If you want to artificially change the colors, I think the best way to do it, is to do it in a selective manner:

1) duplicate the layer of the original photo 2) change the color of the duplicate layer by using the color balance tool to reach the sky tonality you want (don't pay attention to want happens to the rest of the photo)
3) apply a layer mask to the modified layer (hiding all the modified layer)
4) select a brush with proper dimensions and draw with it over the layer mask: this will reveal the modified layer. If you draw only over the sky region, you will obtain the sky with your colors, while keeping the rest of the image with original colors. You can play with different brushes and different brush settings (I found the opacity setting very useful) and see how to get the best results

If you get tired of drawing manually on the layer mask to keep only the sky, there are ways of getting GIMP to select the sky for you. Basically, you use Decompose to split the image into various aspects (hue/saturation/value, red/green/blue or sometimes others) then use one or more of those layers to help you make a layer mask.

There used to be a wonderful tutorial on that technique by Jenny Drake, but unfortunately the site is no longer online. The Internet Archive has the text of the tutorial but no inline images, but you can read the text here:
http://web.archive.org/web/20050313031704/http://www.photojenic.co.uk/home-page/gimp-sky-colour.html

And Carol Spears wrote a good tutorial based on it which *does* have images:
http://carol.gimp.org/gimp2/photography/sky/compose/

If you can forgive a brief commercial note, there will be a couple of examples of the same technique in the 2nd edition of Beginning GIMP (expected in late December). Now that I see Jenny's tutorial is gone, maybe I'll try to find time to put some of it into a web tutorial ...