There are many nature photographers who use a telephoto lens on a camera with an APS-C sensor. The view angle becomes with the smaller APS-C sensor, 1.6x smaller than with a camera with a full frame sensor, making it seem as if you have a telephoto lens with a 1.6x longer focal length. The Sigma 120-300 mm Sports is the first lens in the Sigma Sports series and resembles its predecessor in some ways.
But with the lenses of the Sports series, you can get, by using the USB dock itself, customization adjustments for the AF speed, AF fine tuning, focus limitation and image stabilization. Our experiences with that customization can be found in the Sigma USB dock review. In addition, Sigma recently began offering – for all lenses from the Art, Sports or Contemporary series – the ability to exchange the lens mount. If you decide to buy a different brand of camera, you can build your own favorite and trusted lens conversions, after which you can use them on your new camera.
Sigma 120-300mm f/2.8 OS Sports @ 300mm, f/3.5, 1/400, 100 ISO

The high brightness and long focal length make the Sigma 120-300 mm lens also extremely well suited for playing with background blur. The Sigma 120-300 mm f/2.8 Sports weighs almost 3 kg. Therefore, you will preferably to work with a tripod. The lens comes standard with a solid tripod collar.

Sigma 120-300mm f/2.8 DG OS HSM Sports @ Canon 650D

Construction

The Sigma 120-300 mm f/2.8 Sports is heavy, big and breathes solidity and reliability in every aspect. That starts with the matte black finish of the lens housing, which we know from the earlier Sigma Contemporary and Art lenses. The Sigma 120-300 mm Sports is extra-well sealed against dust and water splash. The matte black, large lens hood is made of metal.
In terms of construction and weight this lens makes a better combination with a professional SLR camera than with the relatively small and light Canon 650D.There are multiple switches on this lens. The most noticeable is the Custom switch with the choices of C1, C2 and off. The Custom function is programmable with the Sigma USB dock. There are also switches to limit the AF range, to choose between AF and MF and between the different image stabilization modes (off, 1, 2).{insertgrid ID = 289}

Autofocus

The Sigma 120-300 mm 2.8 II has a traditional view window, where you can read what distance is in focus. The drive of the auto focus is lightning fast, even in low light. Most of the focus movement is between 1.5 meters and 10 meters. The minimum distance setting depends on the focal length.
The HSM motor is fast and quiet and can be manually overridden at any time if you want to put the focus point somewhere else than the AF. For manual focusing, it’s nice to work with both wide rings for zooming and focusing. They are close to each other, so that you can operate them with the same hand. Once you have the knack of this – because the lens also rests on the same hand – you can also work at lightning speed without the AF.

Resolution Sigma 120-300mm f/2.8 DG OS HSM Sports

This lens delivers sharp images at all focal lengths and all apertures. At maximum aperture the center sharpness, especially at 120 mm, is visibly sharper than in the corners. You get the highest sharpness for all focal lengths at f/5.6. Above that, the sharpness drops off slowly. However, this is really so little that in practice you’ll get equally good results whether you’re photographing at f/4, f/5.6, f/8 or f/11.Because this lens is so bright, it’s good to combine with a teleconverter. Usually you lose something in sharpness by using a teleconverter, but because this lens delivers such sharp images, that isn’t really bad.

Vignetting

The Sigma 120-300 mm is designed for use on cameras with a full frame sensor. With the smaller APS-C sensor of the Canon 650D, just the center of the image is used and vignetting at all focal lengths and apertures is negligible. Vignetting at maximum aperture is about half a stop. At the smaller apertures the vignetting is so low that it’s almost impossible to measure. Because the vignetting from this bright lens is so low, the use of a teleconverter, which usually not only extends the focal length but also increases the vignetting, is an interesting partner for the Sigma 120-300 Sports.

Distortion

The distortion of the Sigma 120-300 mm is so low that when used on a camera with an APS-C sensor, it will never bother you, no matter what focal length you use. We could measure at the longer focal lengths a slight pincushion distortion, but you don’t really see that in the practice shots.

Bokeh  Sigma 120-300mm f/2.8 DG OS HSM Sports

The great thing about working with a lens with a long focal length in combination with a high brightness, is that the depth of field is so small that distracting elements in the background quickly get blurry. The hairs and whiskers of the otter are razor sharp, but his legs are already blurred. The bokeh in our practice shots was pretty quiet.

Flare

Even without the included lens hood, this lens has very, very good resistance against stray light. The image on the right is a detail from a landscape photo, which was taken directly into the sun. Even right around the sun, there is no reduced contrast visible, and in none of the practice shots did we come across any ghosts.

Chromatic aberration

Lateral chromatic at all focal lengths is so low that in practice you will never be bothered by it.

Conclusion Sigma 120-300mm f/2.8 DG OS HSM Sports test @ APS-C

Pros

• Very high image quality: high resolution, low distortion and vignetting, very low chromatic aberration
• Fast AF
• Very solidly built and beautifully finished
• Built-in image stabilization
• Metal lens hood

  Cons

• Big and heavy
• A price that matches the high quality

We have previously reviewed the Sigma 120-300 mm f/2.8 DG OS HSM Sports on a Canon 5D MK2. Comparing the scores in this review with our previous review, the overall scores are practically the same. Still, there are differences: the resolution of this lens measured with a 21 megapixel 5D MK2, as you would expect, is much higher than what we measured with the 18 megapixel Canon 650D. On the other hand, distortion and vignetting are lower on the camera with the smaller APS-C sensor, making the final score in this review still slightly higher than in our previous review. We said it already in our previous test: this is a unique lens, for which we really only see the dimensions and the price as obstacles to purchasing. With a suggested retail price of just under 4,000 euros, the price/quality ratio is very high.