more about the 17-55

Some background on the Canon EF-S 17-55mm f/2.8 IS USM:

This is a pricey (1179 USD) new lens from Canon that will only work on the Canon EOS 300D (a.k.a. Digital Rebel), 350D (a.k.a. Digital Rebel XT), 20D, and 30D camera bodies. It is designed to be a high-performance, general-purpose zoom lens for these cameras.

Canon describes its image quality as "approaching" L quality, "L" being Canon's designation for its premium lenses, heavily favored by pros. What I gather is that L lenses tend to have vibrant colors, very good sharpness (except for the wide-angle ones), good-for-a-modern-plastic-lens build quality, including on the newer models, weather sealing. They also tend to have relatively large maximum apertures, relatively short zoom ranges, and are big and heavy. All current L lenses (except one found on a point-and-shoot model) are EF lenses, meaning they can be used on any EOS camera (i.e., any Canon SLR made since 1987).

Unlike every other camera manufacturer, Canon makes its SLRs in three different form factors. These are designated by their "crop factor", which is the multiplier you need to get from the linear size of the sensor to "full-frame", meaning the size of a 35mm film frame, or 24x36mm. The three crop factors and the relevant models are:

1.6x: D30, D60, 10D, 300D, 350D, 20D, 30D
1.3x: 1D, 1DMkII
1.0x (full-frame): 5D, 1Ds, 1DsMkII

By comparison, all Olympus DSLRs are 2.0x, Sigmas (a.k.a. Foveons) are 1.7x, and all Nikons, Pentaxes, and Minolta/Sonys are 1.5x.

Wait, it gets more complicated. The 300D (my camera) was the first Canon to introduce a smaller mirror to match the smaller sensor. This, combined with a clever retraction mechanism, allowed a larger clearance between the mirror's path and the back of the lens, which in turn allowed lens designs that extended farther back into the body. Canon calls this "short back-focus" and designates such lenses "EF-S". The first such lens was the EF-S 18-55mm f/3.5-5.6 "kit lens", so called because it was originally only sold as part of a starter kit with the 300D/Digital Rebel.

So, that brings us back to the first paragraph of this post, which alludes to the fact that EF-S lenses can only be used on 1.6-crop (a.k.a. "APS-C" for a short-lived film format of the 90s that was essentially the same size) cameras released after the 300D.

If all this sounds like a nightmare to those uninitiated to Canon DSLR lore, it is even worse for Canon DSLR owners. The strength of the Canon brand is its huge line of lenses, but the vast majority of these were designed with full-frame film bodies in mind. The result is that all the best Canon lenses are not wide enough, yet wastefully large, for the vast majority of current Canon SLR owners.

Nikon owners aren't as much hurt by this. Because Nikon engineers are losers, their cameras are not universally compatible with their autofocus lenses - users have to consult a chart to figure out which lenses fit which bodies. Probably because of this limited backward-compatibility, Nikon committed early on to making a full line of lenses that would appeal to DSLR owners. Two years ago, Nikon introduced the AF-S 17-55mm f/2.8, and it seems to be beloved by pros and semi-pros alike. Shots I've seen with this lens are top-notch among standard zoom lenses - as far as the lens goes. The problem is that Nikon's high ISO noise performance is abyssmal compared to Canon's, so there is tons of "grain" in handheld low light shots, which is the primary application for a 17-55mm f/2.8 lens. Furthermore, the price is $1250. When compared to Nikon's new 18-200mm f/3.5-5.6 VR at under $800, it's a hard sell to non-pros - that is, most of their customers.

Enter Canon's EF-S 17-55mm f/2.8 IS. Consumers love IS (image stabilization, which Nikon labels "VR"). Open-minded pros seem to like it too. Plus, the new Canon is lighter and about $70 cheaper than the non-IS Nikon.

On the other hand, Sigma makes an 18-50mm f/2.8 lens for about $500, that's been available for some time now. Tokina and Tamron will be releasing similar lenses this year, probably for a similar price. That's less than half the price of either first-party lens. What gives?

Well, in the case of the Nikon: image quality. I don't care how versatile a lens is: when the prices cross into four figures, image quality is the primary criterion. There's also the autofocus system: both Canon and Nikon have their excellent ultrasonic focussing motors in their lenses, but Sigma does not. Finally, there's compatibility: Sigma has a track record for having their reverse-engineered lenses not work on new Canon and Nikon bodies. This never happens on first-party lenses.

So what about the Canon? It’s main advantages feature-wise over the Sigma are ultrasonic focus and image stabilization. Would you pay $700 extra for these two features? I wouldn't. And I suspect very few others would too. So it's got to beat the Sigma in image quality or I'll be calling for a return authorization.

That's not going to be easy. The Sigma looks to be a very sharp lens, except maybe in the extreme corners. BUT, it has weak contrast, and what looks to be the usual muddy Sigma color. Canon, on the other hand, has a track record of blurry corners on its wide-angle lenses, even the super-expensive L primes. So what does it mean when Canon describes the EF-S 17-55mm f/2.8 as "approaching L"?

They don't mean the build quality, since the new lens appears to be similar to other EF-S lenses, and is not weather-sealed.

Do they mean L color or contrast? Haven't seen evidence of this so far.

Do they mean the sharpness of their full-frame ultra-wide zooms (the EF 16-35mm f/2.8L and EF 17-40mm f/4L)? I sure hope not, because from sample shots I've seen, these are mediocre lenses, despite the high prices.

Do they mean the sharpness of their full-frame standard zooms (the EF 24-70mm f/2.8L and EF 24-105mm f/4L IS)? I hope so, since these seem pretty good. The MTF charts indicate that the EF-S 17-55mm f/2.8 is a match for the EF 24-105mm f/4L on a full-frame camera - the 24-105 being a little better in the center, the 17-55 a little better in the corners. I'd be happy if reality matched the MTF charts.

Well, we'll find out soon enough.