Chip Louie wrote: > Now that's interesting! For those who have an interest and > take the time to view this page realize that the Sigma > SD9 digital camera used for these "tests" has an even > smaller sensor than the Canon EOS D30/D6010D family, the > lens factor is 1.7X. The reason I mention this is that even > less of the problem prone areas of these Sigma lens' image > circle will be visible in these "test" images. > > There is also no mention in the text if these are full > frames (100% or some other res.), center or edge crops. > These images are approx. 200x200 pixels and don't > demonstrate much except how far down the Sigma > lenses need to be stopped in order to get a decent > image out of them when mounted on a Sigma SD9 digital > camera. Is this a problem with the Sigma lenses > that is being tremendously amplified by the Sigma SD9 > digital body or is this typical for the Sigma lenses shown > on the site? I KNOW that some of these Sigma lenses > are much better than is being shown on this page but where > is the problem? > Lens or body? Anybody else have, used or tested the SD9? ------------------------------------------------------------ Gee Chip, that is the nicest thing you written to me in weeks ;-) I do know that many of my friends who are using digital SLRs such as a Fuji S2, EOS 10D, or Nikon D1X have told me that mo matter whose make of wide angle they are all relatively soft wide open. They try to get the best lens they can to avoid this. >From what I know of lens designs, all lenses improve when stopped down. Fast lenses when properly designed will yield good resolution wide open and improve as you stop down. Case in point the Canon 135F2 L. I cannot speak to this being the norm for Sigma. I can tell you that I had a Canon 70-200F2.8 L (non IS version) on loan from Canon CPS and had a Sigma 70-200mm F2.8 EX and shot the same test targets with each. The optical difference was that the Canon was neutral in color, while the Sigma leaned to the warm side. At all focal length res was the same (I was using film) except at 200mm at F2.8 where the Sigma was only a slight bit better than the Canon. This test was the reason for me buying the Sigma. I could have bought the Canon but I use the 135 to 200 range wide open and wanted the better res. Now this may not be the case with the EF70-200 IS version as I have not tried that one. As to consumer lenses, while not always fast they are typically poor in terms of resolution at widest aperture but very good stopped down. Examples are the EF28-80 and EF28-90. Fair at widest and very good at about F8.
Peter K * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
