When you're capturing a exterior architectural shot the sky is almost as important to the feel of the image as the actual building itself. I think it's often over-looked how much the sky can impact the image - the colour, contrast, brightness, even the shape and direction of the clouds.
Here's the original sky in our sample image from a recent shoot at Beach Houses.
The image above has already gone through compositing (touched briefly on an earlier post here). The main thing left to do now is replace the sky with something a little sexier and will help pull more attention onto the building itself. Right now there's an overcast sky with some nice blues, oranges and purples but we need to give it more pop.
Here's the mask used to replace the sky in this image:
The process I used to create this mask is through the colour channels in Photoshop. Selecting the blue channel gives you a black and white image with higher contrast between the sky and the rest of the image (most of the time). You copy this to another layer and up the contrast even more so the sky is completely white and everything else is totally black - tada! you've got an awesome selection mask for the sky. It's really great for those tricky tree situations.
The real challenge is to replace the sky with something that's still believable. You don't want to have a sunset sky when the image was takes at noon for example.
Here is the final image:
Very little is different from the top Original Sky image from final image above, except for some minor touch-ups and colour tweaking.
If you have any comments or questions, please leave it in the comment section below. I love hearing feedback.