How to get these astonishing blue sky photos

[kameleon]

I would like to know hot I can get some of these astonishing blue sky photos, if someone knows, or if someone knows some tutorial on internet about this.

Those photos can be seen on this link:
http://www.shutterstock.com/s/sky/search.html

[Anbesol]

looks like a lot of those used an overlay gradient filter, and most of them seemed to use a blue colored layer in overlay. AdobeRGB is the goto colorspace for most everything, but when it comes to vibrant accurate blues, thats the one thing sRGB does better.

[Don Kondra]

The non photoshop way is to use a circular polarizer but for best effect you must shoot with the sun at your side, ie. ninety degrees to the sun.

Cheers, Don

[Medley]

This very well may have been a gradient overlay filter, but there is a way to get the same effect with much more precision (or, at least, less work) than a gradient can provide.

I suggest you Google a tutorial using the phrase "Lab color boost".

Here's an example. I took this at a local airshow last weekend:


I converted to Lab mode, and did a relatively simple Curves adjustment. Choosing the 'b' channel, I applied the following curve:


and here's the resulting image, after converting back to sRGB mode:


Simple adjustment, dramatic effect. HTH.

- Joe U.