Sigma 28-300mm F3.5-6.3 MACRO lens...Ultra compact dimensions, length: 3.3", diameter: 2.9", Filter Size: 62mm and a 10.7:1 zoom ratio make this lens the ultimate traveling companion. This versatile, all-purpose zoom can capture a wide ranging series of subjects using its wide angle, ultra-telephoto and close-up capabilities. It incorporates 2pcs Special Low Dispersion SLD glass elements and 4pcs Aspherical Lenses, to produce a high level of optical performance. Aspherical lenses provide excellent correction for all types of aberration while making a very compact construction possible. This lens has a minimum focusing distance of 50cm (19.69 inches) at all focal lengths. Equipped with a macro mechanism for close-up photography at 300mm telephoto, with a reproduction ratio of 1:3. It is equipped with a "zoom lock" to prevent the zoom setting from being changed inadvertently. It incorporates an internal focusing system, which eliminates front lens rotation, allowing the use of polarizing filters and Petal type hoods. The lens materials used in this new lens are lead and arsenic free ecological glass.
1 Very pleasantly surprised.
I'd heard a lot of bad things about large "all-in-one" zooms like this. I'd also heard that Sigma was lagging behind Tamron in this type of lens. So I was doubly surprised to find that the Sigma 28-300 macro lens is not only sharp at all focal lengths, but that it is MUCH better (especially at 300mm) than a Tamron 28-300 XR LD that I compared with it side by side.
(I should point out that Tamron has a slightly improved "Di" version of the lens I tried, which has improved lens coatings and might be slightly better. But I doubt it beats the Sigma.)
This lens is even sharp wide open at 300mm (f6.3), a real pleasant surprise. This means it's not an automatic disaster if I forget to stop down, or am unable to. Of course, the edges and corners do sharpen up with the smaller aperture, but they're not bad to begin with.
There is only one thing I hate about this lens: the bokeh, i.e. appearance of out-of-focus points of light. At wide open aperture, small bright spots sometimes look like donuts with spots in the middle - rather distracting, and reminscent of a mirror lens. As you stop down, this effect goes away (which you can't do with a mirror lens) so it's not a deal-breaker, but is something to keep in mind. If you shoot a lot of photos near water near sunrise or sunset (when you're particularly prone to get reflections while using a wide open aperture)you should not buy this lens, because the bokeh will drive you nuts.
Also, the autofocus gets temperamental once in a while, which I suspect is due to the notorious Canon-Sigma incompatibility. But most of the time it's not a problem on my camera (EOS 300D digital rebel).
Despite its limitations, which for me are mostly tolerable and able to be worked around, I gave this item 5 stars because there is absolutely nothing on the market that beats its combination of price, small size, convenience, and performance.
2 Overall good lens
I got this lens for about two months and tried in different lighting situations. My overall impression is that this is a vey convenient lens and saved you lots of trouble ccarrying around many lens. Two problems are obvious: barrel distortion at wide angle (under 40mm)is too serious (this I compared with Canon's 28-135mm); the squeaking sound of AF (even in one shot) is annoying. For me, this would be a transition lens.
