I have the 18-55mm kit lens as well as a Sigma DG 28-70mm lens. When I use the Sigma lens on the camera I am unable to use the Fn button ( to change pictures modes: snow, pets, kids, etc) does anyone know why this is? When I use the kit lens, I can choose the modes, just not w/my Sigma. Also, with my Sigma (which is the lens I prefer) whichever setting I have it set on, occasionally when I press the shutter button, I can hear the camera click and it is almost like it doesn't take the picture. The camera makes a small mechanical noise the entire time it is "taking the picture". I have to turn the entire camera off just to make it stop. It is almost like taking a picture in low light and the shutter is staying open longer. (at least that is what it reminds me of) There is nothing wrong with the camera so I don't know why it would do this. It doesn't do this all the time but when it does, it is very irritating. Of course, this could be something I am doing wrong - I wouldn't be surprised if it was! But I would just like to know. If anyone can help, I'd greatly appreciate it. Thanks so much!