Posted 21 October 2008 - 12:12 AM
First of all, you want to forget anything about brand loyalty. Everyone's going to come on here and say I've got a Canon, Nikon, Olympus, Sony, blaa blaa blaa...
Go to a camera shop and try them out. If they don't let you, then the shop's not worth your custom. They've all got their upsides and their downsides, Sony are still relatively new on the scene but they've taken over from Minolta so there's a lot of history backing them up, so don't dismiss Sony's Alpha series.
See which menus you like, see which ones you don't. Try taking a few photos from different positions, see if it annoys you in any way. Check the weights, if you're going to be carrying it around with you lots then maybe the weight will be a deciding factor. If you don't imagine having to carry it a lot then weight doesn't need to be at the forefront of your mind.
Talk to the sales assistant. Ask questions about the noise in the photos. I know the Nikons that were out a couple of years ago had problems with noise at higher ISOs. Not what you want if you're going to be printing off A1 size photos. If you're not then it doesn't matter. Ask what the battery life is like.
If you're definitely interested in the Canons, then see what it is about the 450 you prefer, it's always good to buy newer technology but if there's nothing there on the 450 you can 100% say, "I'm going to make full use of that," over the 400 then go for a used 400. It will be cheaper and you may be able to buy a body with a couple of lenses or a decent flash for the same prices as the 450 with the kit lens.
Also, if you envisage using it a lot, have a look at battery grips, or spare batteries, how much are they? If you definitely want or need one, will it be better to buy a different make and take advantage of the cheaper accessories...?
You don't need to worry too much about the price of lenses and flashes for Canon and Nikon because Sigma make compatible lenses and flashes that are cheaper and personally I think just as good quality, but what's the availability for the other brands?
It's not a decision I think you can take lightly, it's a lot of money and I think brand loyalty clouds people's judgments. Also remember, when you buy one body, and then over a period of ten years you build up a collection of compatible lenses, flashes, etc etc, you don't want to suddenly decide, oh hey, I actually always wanted a different one, and now suddenly all my kit no longer fits....
Finally, I have a Canon EOS 400D, and I love it, but you may not.
My opinion of my camera is that everything works just how I want it to, I've always used Canons so the menu system felt brilliant. The only things that annoy me about it are, setting a custom white balance is a pain in the arse, the rubber surround on the viewfinder sometimes come loose, and the screen gets very greasy from my face, but then perhaps I should use less face cream....