Wednesday, March 05, 2008

On Lenses

I took a long, critical look the other day at some of the photos I'd recently taken with my Canon 17-85mm lens [left]. It's built for digital and as such, can't be used on any 35mm or full-frame censor CCD cameras (such as Canon's 5D - not that I have one!).

I've had it a couple of years, bought as a replacement for the original 18-55mm kit lens which came with my EOS 300D in 2004. That lens was pretty ropey - very plastic and the image quality was far from great.

Now I'm using my Canon 30D, I've begun to notice that the 17-85 lens isn't particularly sharp around the edges, especially at the wide 17mm end. It also suffers from chromatic abberation:

[Buttsbury Church wide angle shot looks OK at web resolution]

[Detail of the trees on the left]

As you can see, this 100% view from a section of the trees on the left shows a distinct magenta halo on one side of the birch trunk and a slight green halo on the other side. When trying to make prints at A3, these lens "features" are beginning to be irritating...

So I have been thinking about a better lens for my short/standard zoom. I initially looked at Canon's 24-70mm EF f/2.8 L USM but it costs nearly £900, so that was out of the question. I finally settled on the Canon 24-105mm EF f/4 L IS USM [right]. Yes it's a stop slower than the expensive lens, but has the bonus of Image Stabilisation, and f/4 is still pretty fast, especially as it's throughout the zoom's range.

And the L stands for Low Dispersion glass - Canon's best quality lens. On paper my old Sigma 135-400mm lens had a similar spec to the Canon zoom I now use for rugby, 100-400mm EF f4-5.6 L IS USM, but the pictures the Canon produces with that "L" quality glass are so much better. So I thought another L-series lens would be a good investment. Particularly if I ever get myself a Canon 5D full-frame D-SLR as my existing 17-85mm EF-S won't fit.

I had the pleasure of trying out the new toy this morning, taking a few quick shots on the way home from Chelmsford. So far, I'm impressed; the image quality seems first rate. I haven't yet missed the extra 7mm range at the wide end, but am glad of the extra 20mm at the tele end of things.

[Can Impression #2 shows buildings and blue sky reflected in the River Can as it flows through a concrete bit of Chelmsford]

[Branches shows a 100% enlargement of another image taken at the wide angle. Not sure I can see any chroma artifacts in that!]

Of course, I've yet to give the lens a proper run out, but I'm certainly happy with its first impression. And I'm rather pleased with today's Picture of the Day, Covert Surveillance, taken with the new beastie on the way home from the shop!