Compatible converter.
 

I am using a canon100-400is lens on a canon 10d and find I need more reach, especially for bird photography. I am thinking about a 1.4 or 2 x converters, probably 1.4.I like the sigma 1.4 converter, but I do not know if it is compatible with this set up. Any advice would be very much appreciated. Thanks John.

I was discussing the very same thing yesterday and was advised that I would lose too much DOF with the 2x tc and should stick to 1.4x tc.

I am going to borrow a tc later this week to experiment with so will decide after that.

Let me know how you get on.

Rin x

Yup, the Sigma 1.4x does work with the 100-400L.

You will lose autofocus unless you do the trick of taping the pins (do a Google on 'autofocus pins taping' to find the details of this trick). However, AF will be very slow. Yesterday I tried it with a friend's 100-400L and Canon 2x converter. AF was terrible, requiring a bright, contrasty subject at 100mm and not working at all (in fairly dim conditions) at 400mm.

If it is f4 max then AF is usually retained. Above that it's all manual :-(

Rob.

a reasonable image can be obtained using a 2x with the 100-400 but good light is needed and a tripod is recommended.But I find it is difficult to judge if one has the mf spot when viewing through the viewfinder esp on the 20d

With the 2x on a 100-400 it's going to be vital that the dioptre adjustment on the viewfinder is set perfectly for your eye. Otherwise it'll look as if it's in focus when it ain't.

Thanks everyone. It looks like I will settle on the 1.4 converter and practice with manual focus. I managed to borrow one this week and although the weather was totally unsuitable I managed a couple of shots good enough for identification purpose. The only thing I have to decide is if the canon extender is worth the extra cash.

Wow, how educated you all are. I am watching this thread and learning all the time.

I have gone off the idea of a 500mm lens as all the feedback I am receiving states that it is way too heavy for and held photography and I am not a lover of wandering about with my tripod.

I am interested in the 100-400 lens though. But wonder if a 400 prime lens would be better. I am keen on birdwatching and am looking for a lens to take bird photographs bearing in mind how far away they can be.

I am somewhat confused and as you suggest would love to try diffent lens' but we live in the very north highlands and don't have that option.

Keep the advice coming.

Rin x

Hi Rin.The converter I borrowed I used on a 100-400is,it was a sigma1.4 and was hand held,it would have been better on a tripd,especially using manual focus but the shots were good enough to id the birds.