These are both fine lenses. At least, I know the 100-400 IS is because I have one, and I know the 70-200/4 is becaue my son has one, and I am prepared to take it on trust that the 70-200/2.8 IS is. To make a sensible choice (or a different one altogether) you do need to think about how you are going to use the lens you buy; it is a big investment, and also, as you may not fully realise with your present lightweight outfit, a big investment in effort to carry it around.
The word on extenders seems to be that the 1.4x works fine on anything it will fit. I even use it on my TS24 to good effect; sadly Canon do not support this very effective combination by providing the extra contacts. The 2x, however, is a device for prime lenses, and the comparison between the 100-400IS at 400 and the 70-200IS x2 at 400 (the URL has been quoted in this thread) suggests a significant loss of quality with the extender. I use the 100-400 mainly for wildlife. It is almost the perfect game-park lens for hand-held use from a vehicle for animal shots, and although no lens is ever long enough for the birds, with the 1.4x extender it does a pretty good job. The main defects are a fall-off in quality (from excellent to merely very good; nobody is claiming it will compete with the 400/2.8) beyond 300, and significant vignetting at full aperture at 400, plus of course the clumsiness of the (probably inevitable) push-pull design. ... RS __________________________________________________ Do You Yahoo!? Everything you'll ever need on one web page from News and Sport to Email and Music Charts http://uk.my.yahoo.com * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
