Monday, 3 May 2010

Canon 28-70mm f/3.5-4.5 II: X is the Third Consonant

Canon 28-70mm f/3.5-4.5 @ 28mm, f/3.5, Canon 5D MkII

Today I'm going to have a look at an absolutely ancient lens from the early days of the Canon EOS system. The 28-70mm f/3.5-4.5 was part of the launch range, and was a bit odd at the time; the other early EOS zooms were larger, push-pull designs, whereas the 28-70mm had a turny-zoomy ring of a style that is very common nowadays.

In common with all the pre-digital EOS lenses it has full-frame coverage. It begat a short-lived 28-80mm f/3.5-5.6, which in turn begat the 28-105mm f/3.5-4.5, which in turn begat the 28-135mm f/3.5-5.6 IS, which is still sold today. Most of the early EOS lenses are forgotten nowadays, although a few still have a following; people still speak highly of the 80-200mm f/2.8 "magic drainpipe", which was launched in 1989, and the 28-70mm itself has a tiny bit of a cult.

Canon 28-70mm f/3.5-4.5 @ 42mm, f/4

The only extensive profile of the first-generation EOS zooms is here, at the ever-handy The 35-105mm f/3.5-4.5, 50-200mm f/3.5-4.5 and the 70-210mm f/4 all have interesting specifications, but the internet is full of people asking about the lenses rather than taking photographs with them, so I have no idea if they are any good or not. EDIT: Or at least I didn't back in 2010; since writing the above I bought a 70-210mm f/4, and it's not bad. Similar to the 28-70mm, in the sense that it's not great on a full-frame camera, much better on an APS-C camera, and the colours are nice.

Canon 28-70mm f/3.5-4.5 @ 28mm, f/8, Canon 5D MkII
Polarising filter for great justice

A full-sized crop from near the centre of the above image
0, 0.5, 100 unsharp mask

A full-sized crop from the extreme bottom-right corner of the above image
0, 0.5, 100 unsharp mask

Nestled amongst them is the subject of today's post, the Canon 28-70mm f/3.5-4.5 and its MkII sequel. They have a very small cult, which amounts to a positive review on, in the context of APS-C sensors, and some scattered posts on I was curious to see what it was like on a full-frame camera. The dreamers of the day are dangerous men, for they may act their dreams with open eyes, to make it possible. This I did.

The 28-70mm f/3.5-4.5 has always been overshadowed by the later, top-quality 28-70mm f/2.8 L, which has the same zoom range and dominates Google's search returns. The f/2.8 L is made out of metal and is apparently wonderful. The 28-70mm f/3.5-4.5, on the other hand, is mostly plastic, although it has a metal lens mount. There are a few physical oddities. The front part of the lens, which has the filter thread, retracts back into the barrel between the two extremes of the zoom range, which makes it hard to put the lens cap on, and impossible to rotate a polariser at most zoom settings. Some polarisers might even get stuck inside the front of the lens. The rear of the lens is sealed by the rear element, and thankfully my aged copy does not have any dust inside. It is small and light and doesn't extend when zooming. As with the 50mm f/1.8 MkII, I am wary of screwing anything too forcefully into the filter thread for fear of breaking something inside the lens.

The 28-70mm dates from the very earliest days of the EOS system, and went through two variations; an initial model with metal gears, and a later version - the 28-70mm f/3.5-4.5 II - which has plastic internals. Mine is the latter type and was built in August 1988, just a year after the introduction of the EOS system. It tested well in the magazines. It was discontinued at some point. I apologise for being sketchy, but there is almost nothing about the lens on the internet. I surmise either that it was sold as a kit lens, but it was too expensive and too good for Canon's taste, or it was offered as a wider upgrade for one of the kit lenses, but no-one bought it because it wasn't wide or long or good enough for professionals and it was either too expensive or not flashy enough for amateurs.

Canon 28-70mm f/3.5-4.5 @ 70mm, f/4.5

Still, what's it like? On a full-frame camera? Hmm? The answer is that it's a bit like Star Trek: The Animated Series; better than it has any right to be, but still not good enough. It's sharp in the centre at all focal lengths and apertures, doubly so at 70mm; it's terrible in the corners at 28mm wide open, but improves dramatically when stopped down to f/8, f/11; it's good all over at 70mm, but on a full-frame camera you'll wish it could zoom more than 70mm. And that it was faster and wider.

Canon 28-70mm f/3.5-4.5 @ 62mm, f/11

Here's an example of vignetting at 28mm wide open and then f/8, shot with a Canon 5D MkII using Live View, the usual:

Culver Street car park. Even the name is like an air strike on a family wedding, an army boot stamping on a human face. By spooky coincidence another man has stood on that spot and taken the same photograph, back in 2006. What is it about Culver Street car park that draws men to it? Apart from the fact that there is space to park cars?

Now the middle of the frame at f/3.5 and then f/5.6. It doesn't seem to get sharper beyond that so I have left off the other apertures:

Not bad. This is a tiny crop from the middle of a 21mp original and I haven't sharpened it. And now roughly the edge of an APS-C frame, again wide open and then at f/5.6 (it doesn't improve at f/8):

There's a bit of CA and it's not bitingly sharp, but it's decent. After CA correction it sharpens up well. Now the very bottom-right corner of the frame, at f/3.5, f/5.6, f/8, and f/11:

Ulp. It's not a low-light lens. For the sake of completeness, here's the same edge-of-frame crop taken with a Canon 28mm f/2.8 prime lens at f/2.8 and f/8, on a different day with different lighting conditions:

Neither lens shines at the extreme corners, but the 28mm f/2.8 shines less because it is a prime lens, and should be better, and it's not. Oddly, it seems to leap from being decent to being soft towards the edge of the frame, whereas the 28-70mm gradually transitions into mush. Compare both with The-Digital-Picture's ISO 12233 crop of the 24-70mm f/2.8L at 28mm, f/8, to see why Canon can sell the 24-70mm at such a high price without feeling guilty (and then compare them with the 24-70mm's crop at f/2.8, which very good).

EDIT: A few months later I shot the same scene with my Carl Zeiss Contax 35-70mm f/3.4, which is one of the sharpest zoom lenses ever made, at f/8. Here's the field of view at 35mm:

And here's the bottom-right corner, a 100% crop with the contrast boosted so that you can see the detail:

It's not a fair comparison. 35mm is not 28mm, and the boosted contrast is flattering. But, heavens, it thrashes the 28-70mm and the 28mm. You can see the rough texture of the wall, whereas it is just a smooth mass in the other images. It's just as good at 70mm.

Digression: The Canon 28mm f/2.8
The 28mm f/2.8 is a contemporary of the 28-70mm - mine was built in July 1987 - and they are like two peas in a pod. They both have five aperture blades and they both take 52mm filters, and from the front they look very similar. The 28mm was never upgraded and is still available new, although I'm not sure why. It's one of the most anonymous of Canon's prime lenses, vying with the 20mm f/2.8 and 135mm f/2.8 Soft Focus in that respect. It's not that there's anything particularly wrong with it; the problem is that every single one of Canon's general-purpose zoom lenses has a 28mm setting, and on APS-C cameras it tends to be overshadowed by the faster 35mm f/2, which everybody likes. I own one because I found a cheap copy, but I rarely use it because my Canon 24mm f/2.8 is much better in the corners.

Still, back to the 28-70mm. Here's the whole frame, from the same viewpoint, at 70mm:

Here's a central crop at 70mm, wide open at f/4.5 and then one stop down at f/5.6. It doesn't seem to improve and I surmise that the 5D MkII's sensor outresolves the lens:

Here's the bottom-left corner at 70mm, wide open at f/4.5, then f/5.6 and f/8:

At 70mm it's very good. I didn't formally test it at 50mm, although I surmise it is in between the two extremes, and greatly inferior to any 50mm prime lens. On an APS-C camera it would be a good-quality 44-115mm telephoto, an odd range but perhaps handy if your only other lens is a 10-22mm ultra wide.

The 28-70mm has a cult because it's better than it should be, and it is available very cheaply on the used market. I can't find any good tests of Canon's 28-80mm, 28-90mm kit lenses on a full-frame camera, although judging by Bob Atkins' profile of the 28-90mm on a Canon 10D, the 28-70mm is much better than them; and judging by The-Digital-Picture's ISO 12233 charts, the 28-105mm f/3.5-4.5 is in turn better than the 28-70mm in the corners, as indeed is the 28-135mm f/3.5-5.6 IS.

All of which makes the 28-70mm a bit of an oddity. If you're serious about photography but your budget doesn't stretch much beyond a used 5D body then a 28-105mm is a better choice, and there are lots of full-frame lenses that cover the 28-70mm's range. For ultimate quality on a budget then a pair consisting of a 24mm f/2.8 and 50mm f/1.8 plus lots of walking backwards and forwards are superior although more fiddly and around seven times as expensive. The aforementioned 24-70mm f/2.8L and 28-70mm f/2.8L are each twenty-two times as expensive and much, much better. Tamron's much-loved, relatively cheap 28-75mm f/2.8 is also much better - I bought one myself - and it makes a certain amount of sense on an APS-C camera as a kind of short portrait zoom.

Post-Match Ponderances
I subsequently bought a Canon 10D, a 1.6x crop-sensor six megapixel digital SLR from 2003, which I have converted to infrared and will write about in a subsequent post. I briefly tested the 28-70mm on the 10D whilst it was still a visible light camera, and it was essentially sharp in the centre at all focal lengths, and sharp across the frame at f/8. Unfortunately the combination of f/8 and 44-115mm is neither here nor there. The combination of narrow aperture and odd zoom range defeats most of the reason for using a digital SLR rather than a good-quality compact; I want narrow depth of field and I want to go wider and longer than a pocket camera with better image quality. The 28-70mm f/3.5-4.5 only gives me some of that, and I want it all.