I am new to the forum and digital photography. Recently I submitted a photo to a contest. Surprisingly I placed. I was asked a question about the size of the photo and I was caught off guard. I almost do everything automatic. When I down load a photo I resize it 640 x 480. My question is how far down do we resize a photo that might blow up to a 20 x 30 canvas? I am working on understanding the fundamentals, and mechanics or my camera and digital photography. Any help on this would be appreciated.

I joined the site a couple of months ago and have been observing the site. I go by Rollerman because of my love for Roller Pigeons. They flip over backwards in a fast motion. Think of a yo-yo spinning in a circular motion this is what they do. We have state, national and world competitions. I just got a Nikon D7000 and somewhat intimidated by the mechanics of the camera. Here are a couple of pictures I have taken.

Just hunt! Between the birds coming in get some shots in with the camera. I use a 70-300mm lens. When you do knock birds down and the dog starts working have fun. Good light at dawn. I attached a couple of duck hunting pics.