[murfie]

Originally Posted by Gonefishin

Hi All
I’m new to the Forum but not to the Mag.
My interests are sport and nature photography.
I have a couple of questions for you and would welcome you opinions

I’ve just upgraded my camera from a 350D to a 50D and find that my 100/300 lens that I bought aeons ago with my EOS10 film camera whilst OK on the 350D no longer cuts the mustard on the 50D.

I’mtherefor in the market for a new lens and can’t make up my mind between the Canon 100 / 400 L Series and the Sigma 120/400 APO (not EX) lenses.

The recent Sigma review in the mag made no mention of the apertures / focal lengths which provided the sharpest pictures.
I note that neither is the actual focal length used ever mentioned in published photo information, unless of course a prime lens is used, although this info is available in the meta-data..

With my existing lens I normally shoot at 300mm and f5.6 with ISO adjusted to allow the fastest speed that at least 2x the focal length in use.

What, if any, quality improvements can I expect from each of the lenses when used wide-open at 300mm and 400mm.

Before I splash the cash perhaps my old lens needs a touch of in camera focus adjustment– how do I go about this please