When I take pictures with my T2i/ EFS 17-55mm 2.8 IS lens, the pics are sharp but the sky is always washed out/white on all outdoor pics. I am inexperienced.....but all photos with any of my other lenses (L 100 f2.8 IS/L 70-200 f4 IS/sigma 8-16mm) have great color....a blue sky instead of a white haze. What am I doing wrong? Any advise would be appreciated. Thank You.

I was going to say that you were probably shooting a lot wider with the 17-55 than you are with 70-200 or 100mm but then I saw that you have the Sigma 8-16. So my theory that you had a lot more sky in your shots leading to metering issues and the sky blowing out is probably not correct if you are using your 8-16mm the same way as the 17-55.

I guess some examples are going to be needed to see what we can see.