end of lens tests

Alright, I'm keeping the lens. Partly because it's good enough for everything I want to do with it (and outstanding at certain applications), and partly because I'm tired of lens shopping.

My 50mm f/1.4 and kit lens are either going to be donated to my sister or sold. I don't see myself ever using those lenses again, unless I buy a full-frame camera, which will require something to replace the EF-S 17-55.

Here's a summary of my observations after four days and over 2,000 shots with the lens:

• Sharper than any lens I own except the EF 50mm f/1.4 (and possibly the EF 85mm f/1.8 which I haven't compared it with), where the difference is only in the corners. In the real world, the 17-55mm is just as sharp as the 50mm, except for field curvature.


• The lens has pronounced field curvature that shows up occasionally in real world shots. Stopping down hides it well.


• Contrast is excellent - not as good as the 50mm f/1.4, but good enough that the new lens will replace the 50mm in my bag.


• Within the field of focus, it's hard to tell the difference in sharpness between the center and the corners, even wide open.


• Vignetting is obvious even in the viewfinder at 17mm, but it is limited to the extreme corners, and can thus be cropped out if necessary. The vignetting can be compensated for in Photoshop, with all the normal problems associated with pushing a photo more than one stop.


• It's a bit heavy and bulky compared to primes and other consumer standard zooms, but in absolute terms it's not that big or heavy. It's not hard to use all day, but it doesn't feel as nimble as a 50mm f/1.4.


• It does exhibit ghosting of lens elements even when the sun is (just) outside the frame. At f/2.8, the ghosts are small and few; at f/22, there's dozens of them, as well as rays emanating from the light source (the rays are not nearly as bad as those of the defective EF 24-105mm f/4L IS). On the other hand, even with the sun in the frame, the contrast is still pretty good, better than any other zoom I've used.


• I've also occasionally seen ghosts when the sun is almost 90 degrees to the lens axis, something which should go away when a hood is used. This is the same behavior I see in the EF 70-300mm f/4-5.6 IS.


• With the lens' minimum aperture of f/22, and my camera's minimum ISO 100, I cannot blur falling water in sunlight. This is nothing special about this lens, it's a general exposure issue. To get down to f/11 and 1/5s, I'd need a 5-to-6-stop ND filter.


• Conversely, at the maximum aperture of f/2.8 and my camera's fastest shutter speed of 1/4000s, I get overexposed pictures in sunlight. Again, this is just the California sun, not the lens' fault. A 1-or-2-stop ND filter (or a 30D which can do 1/8000s) should solve this problem.


• Purple fringing due to spherical aberration is pronounced at f/2.8, decreasing to almost nothing by f/5.6. It is much better than most consumer-grade zooms I have used.


• Lateral chromatic aberration is visible at 100% magnification, but is relatively mild for a zoom lens (my 50mm f/1.4 doesn't show it at all).


• While the nominal focal length range is roughly accurate at infinity focus, it shrinks markedly at close focussing distances. I did not test all the way to the minimum focus distance, but even so I estimated a focal length range of about 18-50mm.


• The bokeh is quite ugly at close focussing distances, so I doubt the lens would perform well with an extension tube.


• There is barrel distortion at the wide end and pincushion at the long end, but unless your subject is highly geometric with long lines along the image borders, I doubt most people would notice. I know it can be corrected in post-processing, but even without, it's perfectly acceptable for me.


• The focal length range covers practically anything I need wider than my telephoto lens.


• The IS and f/2.8 mean I can handhold the lens in any reasonable lighting situation (even streetlamps at night)


• As far as the lens goes, the focus is flawless and fast enough to capture birds in flight. Like other Ring USM lenses, it is also essentially silent, the only noise being that of the glass moving around.


• The image stabilization is smooth-starting and quick to engage, although not as effective as Canon claims (1-2 stops instead of 3). It is very quiet — much quieter than the grinding stone sound of the EF 70-300mm f/4-5.6 — but not silent.


• The build quality is solid, but not confidence-inspiring. The lens barrel has some play if you apply pressure, the zoom ring resistance is variable, and the focus ring is a bit small and not-so-smooth. There is no zoom creep as of yet, although it looks like it may become an issue as the barrel loosens up. The recessed buttons are hard to manipulate: there's nothing sticking out to push - you have to rely on friction.

My hope was that this lens would make street photography a no-brainer, worry-free exercise. It's not quite there, but it addresses most of the issues I had with my existing lenses. With a little care in selecting aperture and a little post-processing, it looks to be capable of producing flawless pictures in the vast majority of photographic applications. From now on, I will carry around a two-lens kit: the EF-S 17-55mm f/2.8 IS and the EF 70-300mm f/4-5.6 IS. On the rare occasions I go to an indoor sporting event or concert, or engage in portraiture, I will use the EF 85mm f/1.8. Just for kicks, I might add the Tokina 10-17mm fisheye zoom when it comes out. But otherwise, I have all the lenses I need. Finally.