Regarding the photo of Zac who was a bit "yellowed"......The histogram showed that over all the photo was pretty well balanced although there was a definite yellow cast to Zac's fur. Not wanting to blow out any of Zac's highlights I selected him using the Quick mask mode and manually used a Levels Adjustment layer inputting a higher number for the grey set point. The next step was to choose a Selective Color adjustment layer lowering the Yellow slider. I've not used this option before and I think it is going to be quite useful in future editing. I use Unsharp mark on most all photos that I have edited especially after resizing or rotating so most if not all all my images in my homework have been either resized or transformed and then the Unsharp filter used.