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Forum: Pentax SLR Lens Discussion
05-27-2012, 05:55 PM
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I'm not familiar with the Sigma lens, but I would be surprised if it really were a better all around lens than the A 35-105. I suspect there may be any number of problems, including focus errors, camera shake, lack of PP, better in-camera settings with the Sigma lens, and/or non-optimal light, which account for the better images with the Sigma glass. If you really want to compare the two lenses, you can't just take pics of the same subject, you also have to use the same f-stop, shoot from a tripod, shoot in raw, and post-process each image to get optimal results.
I would also note that it's rarely true that one lens is in all respects better than another. The A 35-105 is an old 15 element lens from the mid-eighties. It generally doesn't have as much micro-contrast as newer zoom lenses, because of improvements in coating technology. This means that in harsh lighting conditions the A 35-105 may not produce images that look as good, straight out of the camera, as the Sigma lens. The A 35-105 images may require more post-processing to get the most out of it. And you also need to nail the focus with the A 35-105, which can be difficult because it's a manual focus lens (and focus confirmation is not always reliable). And because it's a heavy lens, it's prone to shake (and SR is difficult to use with it, because it has to be programmed for each focal length used).
The A 35-105 can be a challenging lens to use. It's not prime sharp, and it's not as contrasty as newer zooms. Back when it was still an instrumental part of my kit, I sometimes was frustrated with it, as it had trouble keeping up with my prime lenses. But when at last I decided to find a better option, I had a heck of time finding a zoom lens in comparable focal length that could out perform it across it's entire range.
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