On 10/27/05 9:34 PM, "James B. Davis" <jim@xxxxxxxxxxxxxxxxx> wrote: > On Thu, 27 Oct 2005 19:50:39 -0700, "Joseph Chamberlain, DDS" > <drjchamberlain@xxxxxxxxxxxxx> wrote/replied to: > >> >> 3.2 - The 100-400mm lens offers the obvious benefit of improved telephoto >> zoom range. However, the 70-200mm lenses could be fitted with the Extender >> EF 2x II to transform them into 140-400mm lenses. I've been told that in >> doing so the maximum aperture is reduced and I should be careful since the >> minimum aperture compatible with autofocus is f/5.6. > > I have the 100-400 and love it. I hate having to use extenders, but do > use a 1.4x on my 100-400. Depends what you're shooting but for things > like birds you never have too much focal length. > > The 100-400 is a bit heavy but so is the 70-200. The DO lens is a > novelty that is more compact, but the question remains why? > > The first lens you mentioned, the new one would be an excellent choice > of an all around lens. Personally I have the 28-135 IS and love that > lens too. Much cheaper alternative with a good range and sharp image. > > If you told us what you'll be shooting that would help. First I wish to thank both James and Steve for their replies to my original inquiry. Since I didn't receive too many responses and I am still in the process of selecting some lenses I want to purchase, I decided to add a few more questions to my original post to (1) get some answers that will help me decide and (2) encourage more people to join and share their opinions/experiences. The two questions I have in addition to the original ones are: 1. I understand that autofocus is only supported (at least by Canon lenses) if the maximum aperture is f/5.6 or larger. In case I were to add a Canon 2x extender to a lens that already has f/5.6 as the maximum aperture with the resulting maximum aperture being smaller than f/5.6 would I still be able to use the lens in manual focus mode ? In this case would the exposure metering be preserved through the lens and only the autofocus lost, or would some kind of exposure compensation have to be used ? I would appreciate if those with experience using this type of arrangement could share their knowledge with me. 2. I have looked at yet another lens from Canon. The EF 28-300mm f/3.5-5.6L IS USM seems to be an interesting lens to have. Assuming the image quality is good (and I would hope so since it is an "L" lens), this would be an extremely versatile lens to have, specially if one can also carry a 2x extender in the camera bag (in case the answer to question number 1 above is yes). Any advice and opinions you can share with me will be very appreciated. Thank you in advance, Joseph --- Dr. Joseph Chamberlain Oral and Maxillofacial Surgery
