I was told that with Canon the lenses are interchangeable across a range, whereas nikon bodies have specific lenses. Is this true?
Nope.
Nikon lenses, as long as they are all F-mount and have an internal motor (in the lens, aka G-series lenses, not D) are interchangeable pretty much across every Nikon body ever.
OP: Don't get the D3100 from Game - R7k is NOT a great special. You'd be better off going through The Digital Experience in Fourways, or for really good service: Go through Orms. The
D3100 with 18-55 lens, bag, 2x Photoshop software packages, and free training sessions from NikonSA is R5.5k standard price.
Be aware that the D3100 doesn't have a focusing motor in the body, so when you buy lenses, you have to buy G-series lenses that have a focusing motor in the lens.
If you buy a G-series lens, which doesn't have a focusing motor in the lens, then you have to manually focus the lens for all of eternity. Just know this.
Rather get the D3100 from Orms for R5.5k and then spend the other R1.5k on buying yourself a different, nice, proper lens. Orms has lots of second-hand lenses and specials every so often. I have picked up all my lenses in their Seconds or Specials. I barely ever use my 55-200 lens. I sometimes use the 18-55 kit lens. I mostly use the other lenses I have bought recently - 35mm, 50mm primes.
As to the difference between Nikon and Canon: Both are great quality cameras. Both take good photos. There are minor differences between the two. Either is a good bet.
The main reason people disagree so vehemently over which is better is because, like Nokia vs Sony Ericsson, they simply operate differently. The way the menus work, and the way the buttons are laid out, even little things like the direction you turn the lens to zoom in. On a Nikon, clockwise zooms in, whereas on a Canon, clockwise zooms out. A canon drives me crazy and isn't intuitive for me to use. A Nikon feels right at home in my hand. In the end it came down to personal ease of use.
