Browsing the net I stumbled across a small quantity of new Sigma SD15's on sale for a good deal less than £350! So my frustrating SD14 was put up for sale and provided me with almost the purchase price of a new SD15. My hopes that the SD15 would be a better camera seem to be confirmed. I'd become hooked to the SD range ever since using an SD9, and finding that the image quality is unsurpassed by any other digital camera I had used. So, despite many frustrations with the shortcomings of the camera's ergonomics and limitations, I've struck to using Sigmas simply because the image quality is so superb - distinctive and beautiful. So the old SD 9 gave way to a SD10, then SD14, now an SD15.
I've no hesitation in saying that the handling and ergonomics of the SD15 is much improved over previous models. Overall I liek the general layout of the SD range, its uncluttered simplicity and hefty feel suit me. They are a case where less is more. But the little quirks of handling that used to annoy me have mostly been eliminated on the SD15. Obvious advances include the larger screen, the re-moulded camera back, the re-positioning of buttons, and a new range of customising options (tho these are still very limited). All these changes seem to show that the revisions to the camera have been made by someone who actually uses one!
I think the build quality is good, maybe even excellent. One feature of a camera that gives an indication of build qulaity is the sound the shutter makes. (Having used Leica M series cameras you get spoiled by properly quiet shutters.) I used Sonys and Canons that sound awful - making a real clatter. The Sigma shutter sounds very subdued and very well damped - a 'good thing'.
I can detect little or no difference to the actual image quality of the SD15 compared to an SD14. It is still, at its best, and after patient setting up, utterly delighful. Focusing, however, does seem better with the SD15 - at least with the lenses I have used it is absolutely spot-on, fast and very quiet. Auto-exposure too seems improved and can be trusted with greater confidence than I found with my old SD14. Battery-life may be improved too - although it is still far from what it ought to be.
I can think of only one really convincing reason to buy a Sigma - the end result, the image quality. Not a camera for fast sports use or casual snaps. They need to be used with patience and thought. And then they produce their best. There can be no question in my mind that the results from the Sigma are unique - uniquely beautiful. It's pointless trying to show the true quality of these images on-line - on a computer screen. They need to be seen in high quality prints. Then their distinctive qualities are obvious. Hard to define or describe, but they always remind me of the sort of results I used to get from using Leica lenses on an M6 - wonderful plasticity, depth, three-dimensionality, beautiful colours, astonishingly life-like details, nothing obviously and nastily 'digital' about them. Delightful!
Problems:
Poor battery-life
Very poor quality from 400ASA upwards
Limited lens range - but Sigma do offer a wide range of truly excellent lenses