Canon’s lenses are split broadly into two camps: the standard ‘amateur’ lenses and the pro-level L-series optics. The 50mm f1.2 is one of the latter. It’s a fixed focal length lens in an age when almost everyone uses zooms, and it costs more than a semi-pro digital SLR.

Let’s put this lens’s maximum aperture into perspective. It’s around three stops faster than a typical DSLR kit zoom. In poor light it could let you use ISO 100 where a kit lens might force you to use ISO 800. And in extreme low-light conditions, it could mean the difference between great handheld shots and getting none at all.

The thing about these super-wide apertures, of course, is that depth of field is extremely limited. This is not always a disadvantage, though, as we point out in the Pentax 50-135mm lens review on page 102-103. Shallow depth of field helps subdue cluttered and confusing backgrounds and tends to make the main subject look sharper still by contrast.

This is one of Canon’s EF-series lenses, which means it can be used on full-frame EOS cameras as well as the smaller-format models, which include the EOS 400D and 40D. These EF lenses are not to be confused with the EF-S series optics, which only fit smaller-sensored models.

While the 50mm f1.2 equates to a traditional ‘standard’ lens on the EOS 1Ds, which has a full-frame sensor the same size as a 35mm film negative, on the 400D or 40D it equates roughly to an 80mm because of the ‘focal factor’ introduced by the smaller sensor. This changes its use, slightly, turning it more into a short telephoto/portrait lens on these cameras. But whichever camera you use it on, this is a superb lens for available-light portraits, stage performers and any low-light conditions where you need to be able to shoot handheld.

But the 50mm f1.2 also makes a great studio lens because its resolution is quite stunning.

Even at f2 it’s already producing very sharp results which many lenses would struggle tomatch at any aperture, and between f2.8 and f8 it’s almost certainly limited by the sensor resolution itself. Some ‘fast’ lenses perform so poorly at maximum aperture that they’re really not worth using wide open, but the 50mm f1.2 isn’t one of them. The optics are clearly designed around large-aperture performance, and it’s interesting that the minimum aperture is restricted to f16, by which time the resolution is falling fast.

This is a short lens, but it’s also fat and heavy, thanks to the sheer amount of glass it contains. Canon’s USM focusing is as quiet as ever, though maybe not quite as fast as you may be used to with everyday kit zoom, perhaps because there’s a little more focusing travel. The full-time manual AF means you don’t need to flick any switches to fine-tune the focus.

Build quality is excellent. At this level you can expect to invest at least as much in your lenses as you do your camera bodies, and you can certainly expect them to have a longer useful life. With that in mind, the £1,000+ price tag does look slightly less daunting, but this remains a ‘pro’ lens in every sense. You need to be sure that its optical quality and low-light abilities will repay that investment.

Final Verdict Extraordinary performance, but very expensive and specialised. In low light and in the studio it’s a terrific investment OVERALL

Our lens reviewer, and technical expert, Rod is a veritable photographic encyclopaedia. His illustrious CV has seen him write for many mags, websites and journals.