I like to look up at the leaves of the trees, so I can see them with the sky as the background. Looking at the leaves from the underside exposes a different texture, the backside of the leaves usually have ridges and veins that branch out and become smaller and smaller as they near the edges of the leaf. The problem is if you expose for the leaf, you blow out the colors of the sky, creating an almost white background which I feel detracts from the leaves. In the photo above, I played with the filters in Photoshop CS5. I used the colored pencil filter on a new layer, then inveresed (spelling) the image, creating an image that looks like a pencil drawing.