I love the 24mm focal length. Some of my own personal favourite photos have been taken at 24mm. I often use the wide-end of my Canon 24-70 f/2.8 L, I definitely use my 24mm f/3.5 L TS-E, and, though I sold it when I owned it, I've taken some memorable photos with the Canon 24 1.4 L II. Wait, what? Sold? Yes. While I found the colour and contrast on the lens to be as good as I had ever seen, I wasn't using it to the fullest of it's abilities; namely the widest aperture available on a Canon wide-angle lens.
Wide-angle lenses have a few benefits beyond expanding your field of view. 24Mm isn't so wide that your edges are dramatically elongated or distorted, but not so telephoto that you can't help emphasize foreground objects just by being closer to them. Shorter focal lengths have the added benefit of requiring a slightly slower shutter speed to achieve sharper images. At 24mm I can confidently shoot at 1/20th of a second and achieve desirable results [though 1/30th or more would be better], including potential motion blur of faster moving objects.
Build The Canon 24mm f/1.4 L II is stout and sturdy. It feels like it's built like a tank. A metal body gives it substantial weight and increases my confidence when using it that very little harm could come to it. It has a 77mm front thread, has a weather sealing ring at the rear and comes with a petal shaped EW-83K hood to help reduce flare – something wide-angle lenses are particularly prone to. Full time manual focus is enabled with the lens is in AF and I find the focusing ring smooth in it's movements; certainly good for video.
Image Truly, this lens' optics are some of the best I've experience on a Canon lens. It's not so much the sharpness [though it is] it's the “feel” of the images, the 3D look you achieve on a wide-angle portrait that's near impossible with any similar lenses at f/4 or 5.6. The colour rendition is superb, and the way the lens handles contrast and flare just adds to every image you make. While chromatic aberration and fringing is present in some scenes, it's remarkably well controlled compared to many other L primes.
I've mentioned this in my previous reviews, but I have a personal focus issue. It's not A.D.D., I just have a very difficult time focusing lenses wide-open. I find, when shooting at f/1.4 even with micro-adjustment in-camera, I needed to use live-view to help guide my focus better. Stopped down to f/2 still gives you great results, ones that are better than any other 24mm lens Canon produces.
Something I rarely mind in my telephoto lenses is vignetting. On a wide-angle lens, however, it becomes a nuisance when your field of view covers more area, it almost results in a spot-light effect [see the above image as an example]. Stopping down helps this slightly, but not until around f/4, by then you've also lost a lot of the shallow depth of field appeal that this lens offers. This issue is clearly diminished on crop sensor bodies like the Canon 7D, which married very well to the 24mm lens [giving it a relative ~38mm apparent focal length].
This lens truly shines when your subjects are within the .25m – 3m range. The closer the better to throw the background right out of focus. Where you may have to stop down on some of the zoom lenses from f/2.8 to f/4, you can comfortably shoot at f/2 knowing you've isolated your foreground subject from the background.
Who's it for? Photojournalists and Wedding photographers and any other shooters who find themselves documenting daily, or special, events. Not only is 24mm one of my favourite focal lengths to create environmental portraiture, the extra leverage f/1.4 and it's shallow depth of field buys you will help you isolate your subjects from a potentially chaotic background. The build and relatively small size of the lens will also help you photograph without being potentially obtrusive [of course you may need to move closer to your subjects to frame them properly].
For editorial work this lens would work great photographing your subject in their environment, and then switching to photographic vignettes of your location, focusing on objects and details. The shallow depth of field will draw attention to exactly what you want your viewers to focus on.
I often find myself shooting events, and in tight spaces group photos may need me to use a 24mm focal length, but unless everyone is perfectly aligned I couldn't possibly shoot with this at f/1.4; the versatility of a zoom is useful here, as I often shoot at f/5.6 or so to make sure all my subjects are in focus.
I have seen some incredible astro-photography done with a 24mm f/1.4 lens, though I haven't explored this type of work myself, using the fast aperture with a camera's high-ISO capabilities can allow for unprecedented abilities to gather light, at shutter speeds that to not leave light-trails.
I do not recommend this lens for people involved in real-estate or interior photography, not only is the Canon 24mm f/3.5 L II TS-E built for that kind of work, the extreme vignetting at the edges will ruin an otherwise consistent colour tone on your walls.
Conclusion One of the most impressive lenses I've ever used, in build and quality of images, yet I still sold it. Why? I found myself missing focus very often, this is a personal handicap, and not any fault of the lens. If you live in the world of wide-apertures and can rock a fifty or eight-five wide-open then this lens will certainly lend itself to your style and kit.
On a crop body, even though you're losing much of what a wide-angle lens has to offer, you've bought yourself an interesting focal length that will still work great for environmental portraits, without having to purchase an ultra-wide-angle lens like the 14mm f/2.8 L. For those making a crop to full-frame jump, I suggest you rent the lens first – you may not be used to just how wide 24mm actually is.
As a full-frame user, the Canon 24mm f/1.4 L II will help round out your arsenal. If you already have a kit consisting of primes, or if you feel your zoom just doesn't offer the shallow depth of field you need for your images, this lens will not disappoint.
Shooting wide-open is a choice, and it can certainly produce pleasing results. If that's not indicative of your style, and you're not willing to have a few misses because your focus was slightly off, there are some excellent zoom lenses that can be had for a few dollars more, or even the new Canon 24mm f/2.8 IS – if image stabalization is something you think you need.
The culmination of colour rendition, sharpness, and a shallow depth of field will help you create unique and truly memorable images with the Canon 24mm f/1.4 L II, one of the best lenses Canon has to offer.