Thanks to my wife, I got some nice gift certificates for Henry's Camera. I was able to pick up a Sigma 70-300 DG OS (Optical Stabilization) lens. I was looking at something not too expensive; this Sigma lens runs about $450.00, and has excellent reviews on both Amazon.com and the B&H Video site. If you accept that this is a moderately-priced 70-300mm lens designed for amatuers, you should be happy with it. I think if you start to compare it to Canon's 70-200mm f.2.8 IS II, you'll certainly find weaknesses in the Sigma by comparison, but that model of Canon lens is also about 3 times the price. There are reviews and product spec info pages on the web for this lens, so I'm not doing a big review, just a brief overview. This is my first non-Canon lens for my 7D. As far as aftermarket lenses go, Sigma is generally accepted as producing excellent product. This lens can be used with both full-frame sensors, as well as the smaller APC-s sensors, such as is found in my Canon 7D camera. In brief:
1. Overall weight and build: The lens barrel is plastic, but it has a solid feel to it. The calibrations on the lens are high resolution, matte-white on black lens, which make all of the numbers very visible. Sort of like the matte-white numbers on the dial of the famous Omega Speedmaster watch, which was used in NASA's space program owing to it's legibility under different light sources, among other things. So, I like the very legible calibrations. I like that the lens is not a heavyweight, and wears comfortably on my Canon 7D. It also comes with a lens hood, which has a very matte finish, in order to diffuse light I would think, which is a clever thought by Sigma engineers. What I really miss is a barrel lock; I have not found there to be any lens creep as its called (the lens slowly extending itself owing to gravity as it hangs from at your side), but I have read that in time, the barrel will develop lens creep. All telephoto zoom lenses should come with a simple lens lock, which lock the lens at its shortest focal length, so the lens doesn't drop out while you're trekking about.
2. Auto focus operation: The auto focus is to my perception, a noisier affair than the AF on my Canon lenses. I have read complaints of slowness in the auto focus on other reviews, although I have not yet found this to be the case. I have found the auto focus to be acceptably quick and on target in use.
3. Lens speed. This is not a super-fast lens. In other words, if you want to use this lens to take exposures of fast-action (think sports) in less-than-bright light, you may find it is not fast enough since its widest aperture is f/4-5.6, with the tightest aperture being f/22. In the series of exposures I show here, the fastest I could shoot at 300mm and f/6.3 (the widest aperture I could use with an acceptable shutter speed for some light morning dog-walking action) was 1/100 sec, not fast enough to freeze motion. To be fair, the light was grey and overcast.
4. Sharpness at wide open lens: When I took an exposure of a still subject at 300mm, I found when I zoomed the image 100%, the image detail and sharpness was acceptable. I have read that the sweet spot for image sharpness at 300mm for this lens is closer to f/9, but I couldn't manage it in the light this morning.
5. Color sharpness: When set correctly (I shoot in manual mode all the time, so I try to balance aperture and shutter speed based on my camera's readings moment by moment), I feel that the colors seen in the images I posted here, as well as in the images I've been test shooting since I got this lens, are sharp and correct.
Overall, this is a decent lens for the money. I have read pretty much only positive reviews of this lens. Its prime uses would be for wildlife photography (the main reason I bought this), sports action from the sidelines in good light, and portraiture work, since the 9-blade aperture construction creates some very pleasing bokeh. I look forward to posting more images from this lens in the future.
Photo 1: Lens zoomed out to 300mm; reviewers say that the best aperture for this lens at 300mm is about f/9, but I could not do this in the grey-sky light today. My aperture setting was f/6.3, and the fastest shutter I could get at ISO 200 was 1/100, not fast enough to freeze the action of a running subject.
Photo 2: Cropped section of the moving image, zoomed 100%. The distortion is due to the low shutter speed.
Photo 3: Lens zoomed out to 300mm, f/6.3. On a still subject the sharpness, I believe, is very good. Color here is excellent as well.
Photo 4: Cropped section of the still image, zoomed to 100%. Sharp detail and color in my opinion.
Photo 5. Shot to demonstrate the bokeh of this lens; here, the foreground in blurred, the background fence is in focus.
Photo 6: Opposite; the foreground in focus, the background fence in blur. This should be a really good portrait lens.