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Lots of issues/conditions affect how sharp a picture is. How does the subject lend itself to sharpness. You may have noticed that some flowers just "look" sharper than others. Wind, weather, f-stop, shutter-speed, distance, camera vibration from mirror movement and shutter; and how stable the mounting system is (tripod/head). In addition, lighting, composition and color arrangement are strong factors. It is very hard to judge the sharpness of a lens if the image is not displayed at full-size on a good monitor, especially where lenses are close in performance. A first-generation TIF is by far the best. Sometimes things go wrong and you don't know why. Did you ever take a shot and swear it was in focus and it comes out soft? The question more likely is "How often". Don't expect that every shot you take will be sharp all the time. Whenever a shot looked questionable, I re-shot it. As a rule, you get what you pay for. Don't expect to get "lucky" and get an inexpensive lens that comes out of production above the standard set by the lens manufacturer. It is more likely to be the other way around. A good picture will make a lens look better and vice-versa. Often you can overlook to an extent the faults of the lens if you like the picture. I find AF to be unreliable at and below f4.0 with the SD9/10. Check out the 20/24/28 and 70200 pages as they have AF tests. If you want to shoot wide open, a good magnifier is a great aide in getting the sharpest image. I have the Nikon DG2 which is one of the least expensive ones. I believe Minolta and/or Canon make one compatible with Sigma DSLR's. In addition, I find f22 and above to be unusable with most lenses, the macros being an exception. In comparing lenses, I have found that comparisons may vary somewhat from shot to shot. A good example is the 70200 f2.8 EX/HSM and the 80400 f4-5.6 EX/OS. Even within a picture I have seen one lens look better in one part and another in the other. I shot ISO100, full-size, using a sturdy tripod/head, Nikon magnifier,and MF (unless AF is specifically mentioned). All images are Auto SPP, 100% crops and unsharpened with only a Photoshop levels applied. JPEGS are stored using minimal compression (12) and are either first or second generation. I generally don't show f22 and above as I find these stops to be mostly unusable except with macro lenses. I find that many Sigma lenses seem to have the sweet spot at f11 as opposed to f8. Other miscellaneous lens comparisons can be seen at Other Lens Comparisons |