https://dl-web.dropbox.com/get/Public/hands.jpg?w=d92b8ee8Once you save an image as a jpg you will get rough edges. Editing in PSD or TIFF gives you clean edges in these formats, but when you save the image as a JPG you lose data and will get jagged, rough looking edges. Istock knows this and, according to them, so do their inspectors. However, the best way to check for isolations is to use the same method they use by using a levels or curves layer.
Your image has plenty of issues. I pulled your image, created a curves layer and the first thing is you can see the upper tight grey area. That is a the main issue. However, you also have that light gray around most of the hand, which is unclean. Use your dodge tool, set it to something low like 10 and a good feathered edge. Just kiss the edge of the hand and the gray will disappear. You can do it with the curves layer on or off, but make sure you inspect the image using the curves layer. Once the image is properly isolated, you can dump the curves layer and then save your work.
