All of the above is GREAT and AWESOME advice!
I would take the list that your may or may not get as far as "wishes a camera will do" and take it to a camera center.
Take along with you one or more of his old lenses and take them along. Put them on the cameras there for testing. As a person taking the photos you get a much better feel if the camera is "right" for him.
Tell them what you are looking for.
Most Camera Professional places know that it's a huge investment and typically don't pressure you into buying in the store that day. They are typically very happy to explain things and how they work as well. You can look on-line for certified Cannon and Nikon dealers in your area. Driving a few extra miles to test run a camera may save you a couple hundred or a thousand dollars in the end.
Just browse and compare.
Don't forget to look at the screens and if they make sense to YOU.
Look at the functions it allows you to do in "automatic" mode.
Go outside if they allow you to and take some shots of a moving car for speed comparisons or a bird possibly flying. Or have someone along like a grandchild willing to run a bit for you.
The Cannon 5i and 3i have different features for the user to consider when making their shots.
BUT... Above all else. It comes down to the lens and the camera talking to that lens. You can get a very nice basic camera kit of the 3i with lenses with anti shake at SamsClub or a wholesale box store, however, the lenses themselves don't go down to a 2.8f-stop, so you would want to consider getting an additional lens, so why pay the extra if you aren't going to use what you get in the kit? You don't have to. You can buy the camera body from a local certified retailer or on-line and purchase the lens separately.
Very little known lens secret is that the Sygma lenses were bought out by Cannon and are the only "non-cannon" brand lenses recommended to be used on a Cannon camera and will continue to be branded as Sygma lenses as the competition to Cannon and are a very high quality lens manufacturer.
You also have to consider the RAW file factor in any camera. Raw files let you take all of the data that the camera captures and manipulate it in editing programs, but if you are not someone that knows how to do this, the benefit doesn't out-weigh the cost.
REMEMBER: A Camera NEVER knows what you want to see in your final shot. That is up to the photographer and their knowledge of the equipment and how to manipulate it to get what you want.
Cannon has some nice on-line tutorials and there are thousands of
YouTube videos explaining this and that along with hundreds of published books and websites supporting cannon users.
My personal vote would be to... Go Cannon because I like them. I've used them since I was 15 yrs old, But I have a friend and colleague that loves his Nikon and likes how it function. But YOU have to pick the one that works for THEM, not necessarily the professional, but one that can get you the professional shot.
If professional shots is NOT what they like to capture images for, then camera phones and smaller options like the Nikon with interchangeable lenses may be the better way to go on this one.
There are so many options and opinions and information out there. Good Luck Choosing One!
