![]() Average CA dips down by a fraction from ƒ/4 to ƒ/5.6, but then increases little by little as you stop down – the opposite behavior that we see at the wider focal length, and higher CA than with the bare lens. On the bare lens at ƒ/8, CA was almost double.Īt the middle focal length we tested (193 + 1.4x / 289mm), chromatic aberration is much lower at the wider apertures. At ƒ/8, average CA is less than 150th of a percent of frame height, which is very low. As you stop down, the chromatic aberration is quite dramatically reduced. At ƒ/5.6 with the teleconverter, the average CA is actually lower on this lens than without the TC. Past that aperture however, diffraction softness becomes an issue.Īt 168mm (120mm + 1.4x), the chromatic aberration at ƒ/4 is pretty minor. Even at ƒ/16, the results are acceptable. At ƒ/5.6 – ƒ/8 the images were quite sharp, and more so in the center. As you stop down, the Sigma 120-300 lens + Sigma teleconverter combo produces some sharp images. Wide open at f/4, this teleconverter can produce shar image, notably in the center of the frame. When you get a good copy, this telelconverter produces decently sharp results. This fourth copy was by far the best one we tested, and it's the results we included in this final review. #Sigma lens serial number check serial numbersThe first three has serial numbers that were all very close to each other. ![]() We were eventually given a fourth copy of this teleconverter, which had a higher serial number than first three we tested. Excluding the slight loss in sharpness that comes with any teleconverter, we saw no right side softness with the Canon extender. To rule out any lens issues, we also tested the 120-300mm lens with a Canon 1.4X Extender II, and the results were much better. The third copy behaved similarly, although it was the best of the three. The second copy showed similar results to the first one. We requested a second and then a third copy of the teleconverter. Other than the expected reduced sharpness, we saw significant softness on the right side of the images wide open when using a full-frame camera (notice the difference here at 300mm ƒ/2.8 vs. With the teleconverter attached, however, we ran into a strange issue with this lens accessory. Without the extender, the new Sigma 120-300mm lens produced excellent results ( check out our review). Sigma shipped the APO TELE CONVERTER 1.4x EX DG along with the Canon-mount version of their new 120-300mm ƒ/2.8 DG OS HSM "S" telephoto zoom lens, and we used that lens to test this converter. The Sigma APO TELE CONVERTER 1.4x EX DG ships with front and rear caps as well as a small carrying case and is compatible with both full-frame and sub-frame cameras. Overall, functionally similar to these teleconverters, the Sigma 1.4x extender is significantly less expensive at around $225 compared to the $450 and $499 price tags of the Canon and Nikon extenders, respectively. ![]() For Canon and Nikon, it competes directly against these manufacturers' own 1.4x teleconverters: the Canon 1.4X Extender EF III and Nikon 1.4X AF-S TC-14E II. In the case of any autofocus problem becoming apparent on inspection, we will rectify the situation and make every effort to minimise delay and inconvenience.The Sigma APO TELE CONVERTER 1.4x EX DG comes in Canon, Nikon and of course Sigma mounts. #Sigma lens serial number check freeTo overcome this issue, we are offering our customers an inspection and where applicable, a modification service, free of charge. This is a limited problem that will not occur in any lenses other than those specifically listed above. This issue could possibly occur in some lenses within the following range of serial numbers: Īuto focusing issue affects limited number of Sigma telezoom lensesĪfter thorough investigation, we have ascertained that some APO 50-500mm F4.5-6.3 DG OS HSM, APO 120-400mm F4.5-5.6 DG OS HSM and APO 150-500mm F5-6.3 DG OS HSM lenses, produced recently, may have a potential autofocus defect. I tempted to contact them to see where I stand if something happens in the future out of warrenty if I don't send it back for checking. I've not had any problems but i've only used it a couple of times. I've only found out as my new 120 - 400 comes within the problem serial numbers. There seems to be an issue with a few sigma lenses and the AF on them. I'm not sure if this has be posted already. ![]()
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