One can buy Tokina lens from Tokina, Amazon, Bythom, Ken Rockwell, The Digital Picture, Digitalic Camera Warehouse, Camera City, BH Photo Video and many more.
It will mount fine, and the matrix metering will work. However, you'll only be able to manually focus. The D5000 does not have a focusing motor in the body, and the tokina lens has no internal motor of its own. If you don't mind manually focusing, it's not a problem, but not having AF might suck for sports, concerts, and things that move.
One can easily and hassle-free purchase a Tokina 12 with size 24mm through an online purchase at Amazon's. There, offers cheapest types of Tokia with different types of conditions that you like.
One can buy a Canon SLR lens at several online sites. Some of these online sites that sell a Canon SLR lens are "Amazon", "eBay", and "Bhphotovideo".
There should be a setting in the back or a switch on the outside of the lenes
buy a new one.
One may buy a replacement Nikon zoom lens at nearly any store that carries Nikon brand cameras. For example, one may buy a replacement Nikon zoom lens at stores such as Best Buy or Walmart. Alternatively, one may find them online at websites such as eBay or Amazon.
One can buy a camera lens filter at the Best Buy website. They offer a variety of colors, shapes, and styles for different cameras and video recorders.
If you're purchasing the Canon EOS 5D Mark II digital SLR camera, you can buy it with or without a lens. The lens it is frequently sold with is the Canon EF 24-105mm lens. This is a versatile lens that will be all you need to handle most situations. If you can only afford one lens, this is the one to start with. The Canon 24-105mm lens zooms all the way from wide angle to 105mm, which will allow you to take pictures from twice as far away as a normal non-telephoto lens. For most people, this is the best lens to buy with your new Canon EOS 5D camera.
Tokina manufactures many types of products. Some of them include lenses for many different camera brands including Nokia and Cannon and a variety of other brands.
A lens wont help. You will need to buy a special camera for that.
eBay
Amazon, eBay, and Best Buy are all great places to find camera lens accessories. The websites for Nikon and Canon also carry a wide selection of camera lens accessories.