Banner Images Litle Blurry

I noticed that my banner images are slightly blurry. I am useing a high res image, but it still seems blurry. The product images are perfect though.

Anyone have an idea?

If you upload 2000 x 2000 px images and use 500 x 500 size in the store, they will be blurry due to GDLib compression. Please try to upload images which have size similar to the used one.