by captainkimo » Tue May 12, 2009 5:07 am
The 17-85mm lens is a great lens already. You will find that the 50mm on a crop body like the 40D will limit you. A good way to see if the 50mm will work for you is to set it around 70mm because that's the range it will end up being on your crop body. I have a 50mm 1.8, I love it but I only use it for certain occasions, and that's on my 5D full frame camera!
If you want to go further with your photography, you should identify first the field you want to focus on before buying a lens. Doing this will save you more time and money in the future. For landscape or architectural photography, I would recommend the Canon EF-S 10-22mm but this lens would be useless if you decide to move up to a full frame camera. For portraiture work the Canon 50mm 1.8 is actually the perfect lens but you are limited to one range since it is a prime lens. For a telephoto lens to shoot wildlife or sports photography I recommend Canon's 100-400 IS lens.
Also consider buying a good flash first if you are shooting portraiture.
Cheers!
Captain Kimo