By any standards, this Canon EF 24mm f1.4 is a pretty specialised lens. It’s a fixed focal length optic in a camera world now dominated by zooms, and compared to the average zoom it’s also fantastically expensive. But it does have that f1.4 maximum aperture, and this gives it a two-stop aperture advantage over even a fast, pro zoom lens.

There are two benefits to this. One is that it enables you to shoot in light that’s much dimmer than usual without risking camera shake (or without having to increase the ISO). The other is that it’s possible to create striking shallow depth of field effects, which is normally difficult with a wide-angle lens like this one.

It’s only a true wide-angle, though, when fitted to a full-frame DSLR like the EOS 1Ds Mark III or the EOS 5D Mark II. Like other Canon EF lenses, this can also be fitted to Canon’s smaller-format DSLRs, including the EOS 50D, 500D and so on. Here, though, there’s the usual 1.6x focal factor to apply. This means that on these smaller-format cameras, this lens is equivalent to a 38mm, though this makes it interesting all over again, because now it works as a fast ‘standard’ lens rather than as a wide-angle.

It might be an interesting lens, then, for photographers who own both sizes of body, or who have a smaller-format Canon and want to invest in ‘future-proof’ lenses which can also be used on a full-frame body if they decide to upgrade at some point.

That’s perhaps rather academic, though, since with a list price of just under £1,900, this is hardly an amateur lens. It’s far more likely to be considered by professional photographers who already use full-frame bodies. Even here, though, it’s going to have to deliver something special to justify a price tag like that.

Fortunately it does, on a number of levels. First of all, the definition, using one of Canon’s latest full-frame bodies (an EOS 5D Mark II), is quite staggering. The scale for our resolution charts normally stops at 2,000 line widths/picture height, since few cameras or lenses even approach that. Here, though, the resolution is way above this figure at every aperture except f1.4. The only reason the value drops below this level is because the edge definition wide open is a lot lower (our figures are an average of the lens’s centre and edge definition at any given aperture). Between f2 and f5.6, this lens delivered, in our tests, in excess of 3,000 line widths/picture height in the centre of the frame.

Away from the frame centre, the resolution was lower throughout the aperture range. This lens still delivers very crisp detail towards the edges of the frame, but it’s not at the same level as the centre. And in some shooting situations, this lens’s full resolving power may not be apparent at all. In very low light you’ll be working at or near the lens’s maximum aperture, and while the lens itself will still be sharp at these apertures, there’s so little depth of field that much of the subject will inevitably be out of focus. Also, in very dim light you’ll probably be shooting at marginal shutter speeds, and even tiny amounts of camera shake will take the edge off the definition. Indeed, while this is a fantastic lens for low-light photography, it might be even better with image stabilisation, though there may be technical reasons why this is not possible.

This lens’s outright resolution isn’t its only strength. Zoom lenses require optical compromises that produce unavoidable barrel and/or pincushion distortion, which will go unnoticed in many types of photography, but which sticks out like a sore thumb when shooting buildings or interiors. Prime lenses like this one, though, are simpler to the extent that distortion can be largely eliminated. This is a lens that produces genuinely straight lines despite its wide angle of view, and that’s a novelty if you’re used to the optical limitations of zooms. There’s not much chromatic aberration, either. It's visible to a degree in the high-contrast test charts used for the resolution tests, but scarcely noticeable in ordinary photography.

While a fixed focal length lens is limiting compared to a zoom, you do get used to it. It doesn’t take much to shift your position by a few feet, or to scout around for a better viewpoint – this can actually yield a more interesting perspective, which would otherwise have been overlooked.

The Canon EF 24mm f1.4 is an expensive and highly specialised lens, likely to appeal most to pros who can justify the cost. But even if you’re not and outright image quality is your priority, it’s got to be worth consideration.

Final Verdict This is an exceptional lens at, unfortunately, an exceptional price. It may seem an exclusive choice for pros, though for many the results will be worth the high cost 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.