I am having a bit of a problem. When I receive my product images from my various companies and try to adjust the size on my mac in preview to either larger or smaller for a pop up or thumbnail it becomes blurry. Do I need a different software. I would like to be able to adjust the image and keep the quality. I see a lot of other websites and both the thumnail and the enlarge view( some very big, which is a nice closeup) are crystal clear.

Thanks