What lens(es) should I look at to use with my D40X? I am an amateur, but want to take better quality portrait photos of my child (using the AF-S Nikkor18-55mm, 3.5-5.6 now). I usually just shoot in automatic mode, as I don't have the hang of manual well enough to quickly adjust and capture the moment. A friend suggested 50 mm, 1.4. However, B&H notes you cannot use with D40... same for 1.8. ??? Price is also a consideration. Thanks for any help you can give me!