I mentioned recently that I’d need to sort out a new wide-angle lens for my Canon 5D MK II. After the usual bout of review reading, thinking and price checking, I decided that I wouldn’t (for the time being) get one of those delightfully extreme fisheye lenses that I’ve been contemplating. While I could see one being a bit of fun, it wouldn’t get the amount of use a more general lens would, and I’d rather get the basic kit right first.

I decided that the Sigma 12-24mm lens would do the job as a replacement for my Sigma 10-20mm lens. Now you might think that would mean I was getting a slightly less wide lens, but you’d be wrong.[1] Cameras like the 30D have sensors that are smaller than the traditional standard size of a frame of 35mm film, and so when a lens makes an image on one, the outer parts of it miss the sensor altogether, which means that you see what amounts to a zoomed in version of the image. In short, you have to multiply the focal length of the lens by a number that’s particular to the range of cameras being used. In the case of Canon, that number is 1.6, so a 10mm wide end is the equivalent of 16mm on a full-frame digital (or indeed a 35mm film) camera. So my new lens is actually a good bit wider. How much wider? Let’s see. Here’s a picture I took with the 30D just over two years ago, with the 10-20mm lens at its widest:

And here’s one I took this morning with the 5D and the 12-24mm lens at its widest.

Quite a lot more in that picture, isn’t there? I’ll post some more wiiiiiide pictures later.

[1] People who know about DSLRs may want to skip this overly basic explanation thingy