Change cloudy sky to blue

[GaryHunt1948]

Have photos from trip to Japan and Grand Tetons that are cloudy. Is there a way to change the sky to blue. I have pictures of only sky I have taken that I thought I might be able to use as a layer or in some other manner. Any ideas would be greatly appreciated.

[ofnuts]

1) You have to understand that the photo will look doctored: under a blue sky there are shadows, and your picture likely missing them.

2) If the sky if overcast (uniform gray), add a layer above, put it in "overlay" mode and paint with some rather deep blue.

3) If there are visible clouds:
- add a an alpha channel to the layer ("Layers/Add alpha channel")
- add a layer below and fill with blue, or better find a better sky to graft (must have proper perspective/light direction).
- add a layer mask to the photo layer ("Layer/Mask/add layer mask")
- make the photo transparent where you want the new sky to show, by painting with black
(see here for an example of layer masks at work). Use a fuzzy brush near the horizon.
- when done, "Layer/Mask/Apply layer mask"