June 20 2008

Weight/Build: 63.6oz (compared to 68.6oz of the Bigma http://www.pbase.com/lightrules/image/76360153/original ). Even though the Bigmos is very similar in build and look to the original Bigma, right out of the box it FELT LIGHTER than I expected. It is heavier than the 100-400 IS, however. The Bigmos is VERY WELL BALANCED (especially with a battery grip on the body) and the large tripod collar is a NICE complement to its overall size and weight. Its build and build-feel is VERY NICE, very similar to the Bigma. You can just feel that it's well-built when you mount it and use it. Lastly, the (large) hood is supplied with this lens, but Sigma has moved from the Bigma's metal build to a much lighter but PLASTIC version. While it certainly is significantly lighter, it also does "FEEL" MUCH CHEAPER. Effectiveness should remain THE SAME.

Imaging Quality: The image quality of the new Bigmos is "GOOD". Center sharpness, even from wide open apertures, is GOOD across the focal length coverage (e.g., 150mm - 300mm - 500mm). Border performance, however, like the original Bigma, DROPS OFF and trails the center by about 1.5 - 2.0 stops before catching up. The Canon 100-400 IS performs slightly better at the borders, at least wide open. But again overall sharpness is GOOD and certainly being "only" a 3.3x zoom lens helps in its strong performance across the focal range. Contrast reproduction is VERY GOOD; greens are especially nice and pleasing. The lens does exhibit a slight warm or yellow color cast, but nothing too drastic. Light falloff is SLIGHTLY EVIDENT at wide open apertures, but quickly dissipates even one stop down. Distortions are WELL-CONTROLLED; nothing flagrant at all. Its flare performance is EXCEPTIONAL; I noticed hardly any hot spots or veil-flaring of any kind. And I never even mounted the hood! Lateral (or transverse) chromatic abberations are present wide open but again, it is not flagrant or obvious. Overall the new Bigmos is a GOOD OPTICAL PERFORMER and only slightly inferior to the 100-400 IS. **SCORE 8.5/10**

AF: The AF noise of the Bigmos is VERY QUIET, near silent. This is a good thing. However, the AF speed I am finding SLOW, certainly much slower than I had expected from this "ring HSM" lens. The Bigma is quite a bit faster. It seems that the Bigmos takes about 1.5 seconds to go from rack-to-rack, and this is in bright daylight. **SCORE 6/10**

OS: The stabilization mechanism in the Bigmos is EFFECTIVE and good for 3-4 stops gain. At 500mm (800mmm FOV on APS-C), you can expect shake-free images at 1/100th (3 stops) and even 1/50th (4 stops). Anything below 1/50th on my 40D, I could see shake. With practice and patience, it's certainly possible to do better. Also, Sigma says to turn the OS unit "OFF" when on a tripod. In terms of the quality of the OS unit, I found it quite "unsettling", even after the stated 1-second start-up time. It seems to, arbitrarily, WANDER and move around (you can see it in the VF), more so than I've experienced with other IS and OS units. And then, it will really kick-in, stabilize the VF, then suddenly "wander" again. I think I need more time with it. The OS works, no doubt about it, but it is a "ROUGH" OS unit, it seems to me (in contrast, for example, to the Canon 70-200 f4 IS, which IMO is very smooth and refined). **SCORE 7.5/10**

Value: The new Bigmos rates VERY HIGH on the price-performance index. As mentioned elsewhere, to get a native 500mm (800mm FOV on APS-C), with 4-stop stabilization, ring autofocus with full-time manual override, this kind of build quality, and a beefy tripod collar, lens hood (albeit plastic), and robust EX carry case, all for about $790 USD [Sigma4Less] --- that's quite a deal (or steal). Assuming you can tame the somewhat erratic OS mechanism (practice, practice, practice), you can get some high quality images from this lens. Even though I find the AF relatively slow (tested on both a 20D and 40D), and the OS unit a bit "unsettling", I RECOMMEND the new BIGMOS. **SCORE 8.5/10**