I have a Pentax ist D. I haven't ever felt like I know how to use it! I need help. Feel like pictures are dark even in auto setting. I have tried to go manual and make adjustments and I'm wondering if I've changed settings. Do they stay at what you change them to once you leave the manual mode? I need help with AV and Tv settings. Feel stupid. Wondering about selling and getting another brand. I got the Pentax because I had older film Pentax and was told could use the same lenses. But haven't done that.