The Sigma 300mm f/2.8 EX DG Autofocus Telephoto Lens for Sony Alpha & Minolta Maxxum Series is a high performance telephoto lens and, for the professional photographer, is an absolute requirement. With a fast telephoto lens suitable for capturing the fastest action, whether that is a local soccer game, high school basketball in a dimly lit gym or sports cars racing. This lens also does double duty isolating single faces at a news conference or catching the bride in a candid moment at the wedding reception. Two ELD (Extraordinary Low Dispersion) glass elements provide optimum color correction and sharpness throughout the entire zoom range and a new multi-layer lens coating technology and lens design formula reduce flare & ghosting. When used with full frame cameras & Sigma’s 1.4x or 2x optional Tele Converters it becomes a 420mm F4 manual focus lens or a 600mm F5.6 manual focus lens respectively. For the professional or advanced amateur looking for such a lens at a value price there is no other choice than the Sigma 300mm F2.8. Equipped with all of the latest technology to compete with the camera manufacturer’s products and produces tack sharp end result images.Features: Designed for use with full frame digital SLR cameras. May also be used with smaller APS-c size sensors with a corresponding effective increase in focal length to about 450 with most camerasHSM (Hyper-Sonic Motor) ensures a quiet & high-speed auto focusAmazingly compact. Under 9 inches long & just over 5poundsInner focusing system which enables responsive and fast auto focus speed & overall length does not changeA lens hood, tripod socket TS-21, front & rear lens caps and carrying case are included with the lens. Optimized for Canon digital SLR cameras, the Sigma 300m telephoto lens is a terrific choice for long-distance photography. The Sigma lens relies on two extra-low-dispersion (ELD) glass elements, which combine to reduce chromatic aberration and create sharp, high-contrast images. The multilayer lens coating, meanwhile, reduces internal reflection and minimizes flare and ghosting to further improve image clarity. Finally, the lens includes a built-in Hyper Sonic Motor (HSM) for quick and silent autofocusing, with a full-time manual override for people who prefer more autonomy. The 300mm lens--which is compatible with APO teleconverters (sold separately) for conversion to a 420mm or 600mm lens--also offers a drop-in 46mm filter holder in the rear part of the lens barrel. All Sigma lenses carry a one-year warranty. Specifications Focal length: 300mm Maximum aperture: f/2.8 Lens construction: 11 elements in 9 groups Angle of view: 8.2 degrees Number of diaphragm blades: 9 Minimum aperture: f/32 Minimum focusing distance: 98.4 inches Maximum magnification: 1:7.5 Filter size: 46mm (drop-in type) Corresponding AF mounts: Canon Dimensions: 4.7 inches in diameter and 8.4 inches long Weight: 84.6 ounces Warranty: 1 year The 300mm telephoto lens is widely used in sports and wildlife; situations with poor lighting (such as dusk and dawn for wildlife, and poorly-illuminate gyms for sports) make a fast ƒ/2.8 aperture almost mandatory. These lenses are typically big, heavy and... expensive. Enter the Sigma 300mm ƒ/2.8. Sigma has created a niche by developing less-expensive equivalents to the major manufacturers, available in a variety of lens mounts. In the case of this lens it is available in Sigma, Nikon, Canon, Pentax and Sony/Minolta mounts. The lens is designed to cover a 35mm frame of film, making it compatible with both full-frame and sub-frame digital SLR camera bodies. On a sub-frame body the lens will provide an equivalent field-of-view of 450mm (on Canon sub-frame bodies, 480mm). The lens comes standard with a soft case, tripod collar, caps and a large, round lens hood. Sigma has surprised us in the past, producing inexpensive lenses which perform very well even when used wide open. The 300mm ƒ/2.8 performs well, but never reaches the level of tack-sharpness that other Sigma lenses have produced. Let's take a closer look. Mounted on the sub-frame Canon 20D, the 300mm ƒ/2.8 performs well wide-open at ƒ/2.8, with an average performance of 2 blur units pretty much solid across the frame. Stopping down the lens only improves sharpness results marginally, reaching 1 to 1.5 blur units in a small central region of the frame by ƒ/8, and maintaining 2 blur units into the corner regions. This isn't bad performance by any means, it just isn't the tack-sharp result we've seen on more recent Sigma lenses. Diffraction limiting begins to set in at ƒ/11, with a minor loss in sharpness; performance at ƒ/22 is still quite good at 3-4 blur units. Fully stopped-down at ƒ/32 the lens becomes quite soft, in the order of 5-6 blur units. With the lens mounted on the full-frame 5D, we see similar results, with an increase in the level of corner softness. Wide open at ƒ/2.8, we again see an average of around 2 blur units, just slightly better in the center and significantly softer in the corners - in this case, between 3-5 blur units. Stopping down doesn't do much to improve the corner softening, it just seems to move it around (our sample may be slightly de-centered). Central sharpness improves slightly, but by ƒ/5.6 you've reached the apex of what this lens can offer for sharpness (it's quite similar at ƒ/8) - a small region of sharpness in the center, 1-1.5 blur units, and escalating corner softness - between 2 and 4 blur units. Diffraction limiting sets in at ƒ/11, and again, it's still quite usable at ƒ/22. Fully stopped-down at ƒ/32, results are just as soft on full-frame as they are on sub-frame. In summary, good results on average, but you don't see big gains through stopping down. As well, the Sigma magic doesn't seem to come through on this sample of the lens; there isn't an aperture setting which provides extraordinary sharpness. Chromatic Aberration Results for chromatic aberration are somewhat high, though to Sigma's credit the best performance is observed at the widest aperture setting (ƒ/2.8), where this lens will probably be used most often. As the lens is stopped down, CA increases, especially in the corners. The full-frame 5D seems to be a bit more forgiving of CA, but not by much. I'd check our sample photos to see if the chromatic aberration is objectionable to your eyes. Shading (''Vignetting'') Corner shading isn't much to write home about when the lens is mounted on the sub-frame 20D - the corners are just a quarter-stop darker than the center when used wide open at ƒ/2.8. Stop the lens down even to ƒ/4, and the shading goes away. When mounted on the full-frame 5D however, light falloff is a bit more noticeable. When used at ƒ/2.8, the corners are 3/4 of a stop darker than the center. Stopped down to ƒ/4, this shading is slightly alleviated at just under a half-stop differential, and at ƒ/5.6 corner shading is reduced further to just a quarter-stop. At any other aperture, light falloff isn't significant. Distortion The Sigma 300mm ƒ/2.8 is excellently optimized to produce distortion-free images. On the sub-frame 20D, there's almost no evidence of any distortion. On the full-frame 5D, there is just the slightest bit of pincushion distortion (-0.05%) in the corners. Autofocus Operation Sigma uses its HSM technology for autofocus on its Sigma-, Nikon- and Canon-mount versions of this lens; Pentax and Sony users are limited to mechanical focusing strategies. A full focus movement (infinity - close-focus - infinity) took about 1.5 seconds, though the lens is quite ''snappy'' when focusing between short distances. The HSM-variants of this lens allow the focus to be adjusted at any time by just turning the focus ring; as well, the lens is near-silent during focus operations. Macro With a magnification ratio of just 0.13x and a close-focusing distance of 2.5 meters (over 8 feet), macro users should look elsewhere. Build Quality and Handling The Sigma 300mm ƒ/2.8 lens is nicely built, composed of both metal and plastic construction. Its black matte finish has a roughed texture, making it easy to grip and maneuver. The lens mount (as you would expect for a lens of this size) is metal; filters are the 46mm drop-in type, and a normal filter is included with the lens. This lens uses a convenient system for rotating drop-in filters: there is a thin ring with ridges next to the filter holder that rotates a small gear in the lens, which meshes with a gear on the filter holder to rotate the filter. A white reference dot is marked on the filter rotator ring to give you a sense of how far you've turned the filter. There isn't much in the way of control features on the lens other than the aperture and focus rings; a single switch allows the user to deactive autofocus control on the lens. A recessed and windowed distance scale is provided, with markings in feet and meters, however there are no depth-of-field markings; neither is there an infrared index. The lens aperture is composed of 9 diaphragm blades, which should serve to produce pleasing bokeh. The focus ring is the dominant feature of the lens. The ring is 1 1/2 inches wide, composed of soft rubber ribs which run lengthwise to the lens. The ring turns 180 degrees through its focus range, providing excellent tactile resistance for manual focusing operations: it's nicely cammed, and very smooth. There are soft stops at both ends of the focus spectrum to let you know you've reached the end, but the focus ring will still turn albeit with an increased resistance. The lens can focus past infinity. The lens hood is significantly large, at 3 3/4 inches long. It's a circular-style hood that attaches via a bayonet-mount and reverses onto the lens for storage. The interior of the hood is flocked to reduce stray light from entering the lens. The front lens cap is actually a smaller hood that slides over the front of the lens. The tripod collar uses Sigma's standard design which allows for a quick release. The collar has a single 1/4-inch mounting socket. On the lens, there are two marks serving as 90-degree rotation marks for landscape and portait orientations, but if you want to align the lens in a counter-clockwise position you'll have to use the ''Sigma EX'' logo as a reference point.