<snip> Where I loose track of the discussion is where it is stated that it "wins you two stops" and thus a 4.0 with IS compares to a 2.8. First, the advantages mentioned above are not present in a 2.8, be it bright or low light. Second, as a disadvantage: we are all extremely critical about sharpness (focus) and vignetting. Manufacturers introduce all kinds of complex aspherical elements to achieve optimal performance and it is proving to be a tough job. Yet, with IS we have an element that is constantly changing shape to counteract our movements: what does that do to overall image sharpness? Not to mention that IS does not provide you with a brighter viewfinder (as a 2.8 does). I realise that reducing user induced shake allows for longer shuttertimes (even two stops), but isn't the remark of "winning two stops" leading to comparing apples and oranges, or am I missing the point here? Rick Rick, You forgot one other disadvantage of slow lenses: increased Depth of Field. I shoot with tele's generally wide open, blurring the background as much as possible, to concentrate on the subject. An f/4 lens has twice the DOF as a 2.8 lens. Colin
