The incredible Canon 11mm – 24mm

Walker and gull enjoy the upper Waitemata Harbour, Auckland. 11mm, f/16

Walker and gull enjoy the upper Waitemata Harbour, Auckland. 11mm, f/16

The ages of a photographer may be described by the focal lengths they favour. Henri Cartier-Bresson is famous for only ever using a 50mm lens. In fact, that’s not quite true. There are pictures of him using a multi-focal length viewfinder with what looks like a 90mm lens, and some early images look like they must have been shot with a 35mm lens or shorter. Nonetheless, his maturity was certainly marked by use of a 50mm lens.

I’ve had sport photographers tell me they’re fed up of peering down the long tube of their 400mm or 500mm lenses, and now favour using a 24mm – 70mm lens as the shorter focal length forces them to be either closer to the action or take more of a relaxed, establishing type of shot.

In my case, I used to have nothing but a 135mm lens on the camera, sometimes reluctantly using a 50mm. I never saw wide-angle views, homing in only on detail. So I was very happy when good 70mm – 200mm lenses turned up, and found myself using it mostly at the 200mm end, then I spent a lot of time with the 100mm – 400mm work-horse.

But one day, over 20 years ago, I reviewed a 21mm lens – the legendary Super-Angulon for the Leica reflex. I was enchanted, and found myself wanting to go wider and wider. This wish was fulfilled by the Sigma 12mm-24mm zoom. For years, I put up with the fact that its corner performance wasn’t worth the pixels it was written on, and developed a style that did not depend on corner performance. I even worked out a series, called ‘Caterpillar Views’, which made a virtue of the miserably obvious comatic and astigmatic smearing together with marked lateral chromatic aberrations.

Since starting to use the Sony A7r as my main camera, I’d been toying with using the Voigtlander 12mm lens. It’s cheap and it’s tiny. But images from it would need a great deal of post-processing for which, to be honest, I’m too lazy. There’s always the superb Nikon 14mm-24mm zoom but for me, it was a big lens for not enough wide-angle reach.

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Back to school

Recently, I started to submit again to an agency that has long held a tiny bit of my work, Getty Images. I was nervous about submitting the Sigma photos and sure enough they were hammered by the editor who, as she kindly put it, ‘passed on them’. The fact is, they were simply too rubbish to be considered professional-quality images. So I had a problem if I wanted to work at the sub-16mm end of the spectrum.

Then I learnt about the Canon 11mm – 24mm. This focal length range caused me to double-take, rather like when I first learnt about the Leica 21mm f/1.4. I thought that specification must be a mistake. Well, incredible as it seems, 11mm is, indeed, the shortest focal length and it goes to 24mm with full-frame (24mmx36mm) coverage.

By the time I’d checked out my usual sources such as bhphotovideo.com and the usual ever-active lens reviewers, I was seized with the desperate need to try it out myself. All users had found the optic outstanding. All complained about its size and weight. And all whined about its $3000 price tag.

A big ’Thank you!’ to Canon NZ for the loan of the lens for a couple of weeks. As it turned out, it was clear within the first hour that it was the lens for me. The image in the A7r is bright, clear and easy to focus. This is always a good sign of excellent full-aperture performance. When I uploaded images to my Mac, the remarkable superiority of the lens was just so obvious I did not bother with a side-by-side comparison with my Sigma 12-24.

New performance level

There are several detailed ‘reviews’ of the optical performance of this lens, including a bench test at Lensrentals http://www.lensrentals.com/blog/2015/02/canon-11-24-f4-l-mtf-tests so there’s no need for me to offer my own observations. I’ll just agree with all their enthusiastic evaluations. One of the most impressive aspects of its performance is that both the 11mm and the 24mm extremes are fully useable, as is every step in between. One reason I never used my Sigma at the 24mm setting was that it was horrible at that focal length: essentially I had a 12-20mm zoom.

The lens’ performance profile boils down to these points.

At 11mm, with a field of view of an eye-popping 126º, it is not only unique, it is entirely and highly useable – provided you know how to use it – which can’t be taken for granted. At longer focal lengths it is the match of other, but more easily handled optics like 16mm-35mm lenses. At 24mm it is highly useable, but not quite up to the 24mm end of the Zeiss or Canon 24mm – 70mm f/2.8 zooms.

Full view at 11mm, f/13.

Full view at 11mm, f/13.

Top left hand corner of previous shot.

Top left hand corner of previous shot.

For such a wide-angle zoom, it is remarkably rectilinear in its drawing of straight lines as pretty much straight lines. The engineers designed it so that the geometry of projection varies with distance: if you place a straight line very close to the camera while focusing far away, the near edge is strongly barrel-distorted. But if you focus close up, the edge straightens up a little. This is most visible at 11mm focal length. As distortion is lower with distant lines than with nearby lines, what distortion is present is visually acceptable. But it would be nice to be able to correct. So here’s a request to DXO: please come out with a correction module soon.

Barrel distortion at the near edge at left.

Barrel distortion at the near edge at left when focused further away. Notice how the curve of the edge on the right has greater radius, i.e. is less distorted.

Performance at the very corners at all focal lengths and usual working apertures – i.e. not wide open (why test it wide open when you never use it in practice?) – is remarkable. I have to zoom into 200% of 36 megapixel images to be able easily to see the purple/cyan fringing at the 11mm setting. More importantly, the detail is held amazingly well: sharp, clear and hardly smeared at all, even at 200% or greater. On the Sigma, smearing the corners is visible at 50%.

One of the weaknesses of ultra wide-angle lenses is that they’re inherently prone to veiling glare and to internal reflections because it’s very hard to keep point-source light sources out of view. Veiling glare appears as a haze covering parts of or over the whole image which takes the welly out of colours and fills shadows with mucky light. Internal reflections are images of the lens diaphragm hole which is produced by reflections from the surface of lens elements (which is why you’ve seen a whole series of them in a line of different sizes and colours thanks to varying lens radii and differing coatings). In this lens, they are, again, remarkably absent. If you force it, you can obtain plenty of reflections. And if you allow muck to build up on the lens they’ll be seen as the very short focal length easily brings dust specks on the lens surface into the circle of confusion.

Brilliant control of veiling flare and internal reflections. f/16

Brilliant control of veiling flare and internal reflections. f/16

But you can see from examples here that even with the bare sun on or off-axis, flare and reflections are as well controlled as you could ask for. This must be down to superb lens coating technology as well as use of sophisticated internal baffles (I suspect the move on zooming) in the construction.

Another common weakness of wide-angle zoom lenses is close-up correction. Once again, this lens delivers: nicely at the closest focusing distance. Detail is surprisingly well rendered: tight, sharp, fairly good contrast and richly coloured.

Central crop, focuses to minimum operating distance.

Central crop, focuses to minimum operating distance.

The full view.

The full view.

Hamm. Isn’t there anything I can complain about?

New hold

The main issue with the lens is – as all reviewers have groaned about – its size and weight. At over two and half pounds or 1.18 kg, it’s only a little lighter than the substantial Canon 70mm-200mm f/2.8 zoom and heavier than my hefty Zeiss 135mm f/1.8 lens. In short, you’d better think first before you try to pick it up.

It’s mostly because of that huge chunk of aspherical glass on the front. The engineers designed an extreme retrofocus design in which the short focal length has to travel a long way through the lens –  about 160mm – to reach the sensor. This way, the difference in path length – the distance the light travels – between rays passing near the centre of the lens is not much different from the path length of rays defining the edge of the image. The similarity in path length helps even out illumination at the sensor: it reduces two factors – called the cosine and cosine to power four laws – that cause corners to come out darker than the centre.

In fact, the front element is much less bulbous than you’d expect because its central portion is actually nearly flat – it’s a much greater radius of curvature than towards the edge of the element. This must help even out path length too: the distance between the front of the element to the sensor is less than normal because of the flattened profile.

From its size, the lens looks like it should be well capable of capturing light at f/2.8, but I think it has been limited to f/4 to conserve image quality. I’m sure f/2.8 could have been set as the maximum aperture, but where is that f/2.8? It would deliver f/2.8 correctly only around the centre, and be more like f/7 or less at the image periphery.

I’ve seen posts complaining about the aperture being ‘only’ f/4. Silly. Who, seriously, would use this lens at f/2.8? The same people complaining about its maximum aperture would then complain about the uneven illumination at the sensor. Besides, if you really need the speed, use the right tool e.g.  a prime lens like Canon’s excellent 24mm f/1.4 lens. If you need reduced depth of field, then either don’t use a ruddy great ultra-wide, or exploit reverse Scheimpflug effects with the 24mm or 17mm tilt lenses.

I did find I had to develop a different hold to operate the lens. It looks like you’re invited to hold it near the back, palm on the zoom ring and thumb and forefinger at the focusing ring. But because the lens is so front-heavy, it’s more comfortable to hold it right at the far end of the lens (careful not to have a finger tip wander beyond the lens hood, where it will be seen). Focusing is then achieved with the middle finger alone. That is easy as, it goes without saying, the focusing movement excellent: well damped, smooth and without any slack. Auto-focus is reportedly very rapid on Canon lenses. In my set-up, with a Metabones adaptor, it was slow but for static subjects, auto-focus is useable. Nonetheless, I prefer to work with manual focus, using the Sony’s excellent magnifier feature. Incidentally, it’s handy that the adaptor carries a tripod bush: this allows you to support the outfit closer to the centre of gravity than would be the case if you attached by the camera’s tripod bush.

Best recommendation

Actually, this is not the kind of lens anyone should recommend or dismiss. It is unique, expensive, and demanding to use. It also performs spectacularly well and as free of fault as any optic with extreme specifications could hope to be. It either recommends or disqualifies itself. In my case, I put in a request to my finance department within minutes after using the lens and ogling its images. So if actually buying an optic is anything to go by, I’ve just given it the best possible recommendation.

 
 

 

Here's a tiny section from lens at 24mm.

Here’s a tiny section from lens at 24mm. You can just about make out the time – it’s 12:20 – at even the second hand is just visible: 10 sec past the hour. Whole image is 36 megapixel, captured raw, with no sharpening.

And this is the whole image, uncropped.

And this is the whole image, uncropped. On my 27″ iMac screen, this image fills most of the screen – some 480mm long – while the cropped section (above) showing the watch is just 20mm long. You may draw your own conclusions. I smashed up the piggy bank.

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