Sigma AF 120-300mm f/2.8 EX HSM APO Quick Test Report / Review 02/25/2005 Special thanks to Markus Stamm for providing this lens! Introduction The Sigma AF 120-300mm f/2.8 EX HSM APO is a unique lens - it's the only f/2.8 zoom beyond the usual 200mm barrier. As such it surely produced some headaches in the design departments of the genuine manufacturers - more so regarding the current market price around 2000 EUR which is FAR below 300mm f/2.8 fix-focals. With a minimum focal length of 120mm it is probably a little too long for portraits but it's a great option for action photography. It may be a little unusual to test drive this lens on an tiny EOS 350D but for the sake of comparable test results we naturally go on here. On APS-C DSLRs the field of view is equivalent to 192-480mm. The tested sample is the older non-DG variant. The current DG lens only adds better coating so the findings in the scope of this review should be pretty much representative for both lens variants. The optical construction is made of 18 elements in 16 groups including four SLD (Super Low Dispersion) elements. The lens features 9 aperture blades. The min. focus distance varies between 1.5-2.5m resulting in a max. object magnification of 1:8.6. The filter size is 105mm so be prepared to cry when intending to buy a polarizer for it. The lens has a size of 271x113mm with a total weight of 2600g incl. the detachable tripod mount - nothing for the faint hearted. If you're considering this lens plan some extra exercise in the gym ... The product shot above shows a comparison with its little sister - the AF 100-300mm f/4 EX HSM APO which comes with a far lesser weight penalty (1440g vs 2600g). The build quality of this lens is excellent - both the zoom and focus rings operate very smooth and very well damped and the typical EX finish (smooth crinkle style) helps to maintain a good grip when carrying the camera/lens combo. The lens features a HSM (Hypersonic Motor) AF drive providing a fast and near silent operation. The AF 120-300mm f/2.8 EX is compatible to both Sigma AF EX converters as well as the Canon EF 1.4x II (not sure about the 2x). Distortions Distortions are very well controlled with this lens with marginal pincushion distortions at 120mm increasing to slight pincushion distortions at 300mm. 120mm: 200mm: 300mm: Vignetting Typical for most full frame lenses it produces very little vignetting on APS-C type DSLRs. The issue remains below 0.5EV at 120mm and 200mm even at wide-open aperture. The issue is a little more pronounced (0.63EV) at 300mm - nothing critical and stopping down helps to reduce it to a marginal degree. MTF (resolution) The lens produced some serious headache in the MTF lab. The tested sample suffered from both residual spherical aberrations (focus shift when stopping down at 120mm) as well as high field curvature (at 200mm and 300mm) which makes me wonder whether the sample was actually within specs. Anyway, when taking these issues into account the lens was capable to deliver a very good to excellent center resolution followed by generally good to very good borders. There was a slight but clearly noticeable drop in performance towards 300mm. Chromatic Aberrations (CAs) CAs (color shadows at harsh contrast transitions) are low to very low throughout the tested focal length and aperture range. Verdict The Sigma AF 120-300mm f/2.8 EX HSM left some mixed feelings during the test. On paper the performance figures are quite convincing with a generally very good resolution, low distortions, low distortions and low CAs. The build quality is also impressive. However, at least the tested sample suffered from quite hefty field curvature resulting in blurred borders when shooting flat objects. Unless you need the extra speed it may be a better idea to look a bit down the food chain, namely the Sigma AF 100-300mm f/4EX.