Rob Brigham wrote: >I think we may be at crossed purposes here. I was not talking about the new f1.8(?) big jobbie, but the old and long discontinued f2.8 version. >From your comment about the 'expensive-looking finish' I guess your comments relate to the new EX DG lens.
<snip> Sorry Rob, I should have been more specific. I was talking about the 1990s 24mm f/2.8. I haven't seen, touched or used a 24mm f/1.8 EX DG. Some of the 1990s 24mm f/2.8 lenses had the sexy "Zen" finish which, which Sigma used to hide a truly deplorable mechanical build "quality", at least in the versions with mechanical linkage to an in-camera-body AF motor. I have never even *seen* a version in Canon EF mount, let alone handled or used one, so I can't comment on its build quality. >Not that I would denigrate your comments anyway. I must admit that I never used the Sigma to take pictures, I was just basing my opinion on extensive research done before making my 24mm purchase. The whole web consensus is that this is a great lens with poor mechanics. Well, the "whole web consensus" you mention is (in my opinion) dubious at best. Many are swayed by the apparent sharpness of the lens, supported by wonderfully scientific MTF figures that are more misleading than useful. For example, those people will be happy with any Nikon lens, because Nikon lenses are sharp and get good MTF ratings on web sites. Yet we know that there is a gulf of difference between Nikon and Pentax glass, with the exception of a very small number of Nikon lenses that approach the superb optical performance that you get from the majority of Pentax optics. Most "web opinions" are, in any case, expressed either by people who have never touched the equipment concerned, or who judge it on the basis of 4" x 6" machine prints made from own-brand film bought and processed at Wal-Mart (etcetera). >However, if you are talking about the new lens then I am surprised anyway. Your comments regarding distortion fly in the face of specific tests for just that type of thing in Amateur photographer, and is the first time I have heard it. Could you have had a bad sample? Sorry for the confusion! (see above) I have owned and used three 24mm f/2.8 Sigmas. One was a 1975 "Filtermatic" in Olympus OM mount, the next was a 1980s MF version in Nikon AI mount, and the last was a 1990s AF version in Nikon AF (non-D) and with the sexy "Zen" finish. The Filtermatic was a superbly made lens. It was big and heavy and dwarfed my OM-1 body, but it was sharp. I replaced it with an Olympus 24mm f/2.8 which was a lot smaller (the Filtermatic had *dwarfed the camera!) but no sharper but had poor build quality. It let me down badly twice when the stop-down linkage broke twice on one assignment. The second Sigma was also sharp, but with build quality that was inferior to the Filtermatic. The "Zen" was also sharp, with appalling build quality. Many others I know had the same problem, with the gears in the AF linkage stripping after only a few months' use. I tried to repair it myself once on assignment, then found that the lens was assembled with sticky tape and included rusting steel components. Good grief! Steel! There was also some pretty amateurish soldering ... What *all* these Sigma 24mm lenses had was noticeable barrel distortion. None of them could ever be suitable for architectural photography. The 1990s "Zen" was the worst, and I would confidently describe it as a "semi-fisheye". >I do actually feel the EX lenses are well made though, and that their build problems are largely in the past and in the consumer lens segment anyway. I know many people using the macro lenses and the 70-200/100-300 EX lenses and they have no problems with build. Well, they certainly *look* well made and feel good in the hand. But because Sigma don't licence the technology from the camera manufacturers, not all EX lenses support all of the manufacturers' feature sets. I don't know if there are any issues with Pentax bodies (do they even make these lenses in Pentax AF mount?) but they won't provide all the functions that a Nikon AFD lens has, nor a Canon EF. Rob, you made a comment above about "Amateur Photographer" tests of these lenses. A few months ago, before I switched from Nikon to Pentax, I was interested in the Sigma 15-30mm EX DG. I saw the results of the late (and lamented) Dr Stuart Bell's test of this lens in "Amateur Photographer", and this seemed to be "the perfect lens". The resolution was fantastic, both at high and low contrast (far more useful than those ridiculous MTF tests you see selsewhere) and the lens was even sharp at the edges, despite having been designed for digital SLRs with less-than-full-frame CCDs. Distortion was low too. Then I started getting reports from people I know who bought this lens. They were all unhappy because the results they got bore no resemblance to those in Dr Bell's test. Let me say that I have never doubted Stuart Bell's integrity, and I am not about to now. But the Sigma 15-30mm EX DG you buy in the shops appears to be an entirely different article to the one he tested, and production variation does not appear to be the explanation. There is some strong confirmation of the poor optical quality of the 15-30mm EX DG on (if I remember correctly) the photozone.de site. >I hope we do meet up soon and we can have a good debate over a few beers on this!!! Careful, Rob, if encouraged I can go on for DAYS! John
