Canon 300mm F4

[glsammy]

Whilst I agree I had the same problem when I use the Kenko with the 300mm I have no problems at all when I use it with other lenses. One is just about permanently on my Sigma 150mm. The optical quality of the Kenko seems to me to be first rate.

[BillyPilgrim]

Originally Posted by glsammy

Whilst I agree I had the same problem when I use the Kenko with the 300mm I have no problems at all when I use it with other lenses. One is just about permanently on my Sigma 150mm. The optical quality of the Kenko seems to me to be first rate.

I agree completely.

I have the Kenko almost permanently attached to my Canon 500mm lens and it works perfectly. I'm going to revert back to the Canon 1.4x though as I want to be able to use it with the 300mm as well.

[johnf3f]

Originally Posted by glsammy

I've started experimenting using extension tubes to allow me to use the 400mm for smaller insects. So far on the few occasions I've tried it it worked quite well.
Here's one I got earlier this year:

Nice Image - shows what the 400 will do when necessary.
I agree the af on the 300 f4 (at least on mine) is not stellar, though it improves on fast subjects (such as birds) if you turn the is off completely. However when it nails the focus the 300 can produce stunning images that allow a lot of cropping before the image is compromised. So far I have not had much luck with my Canon 1.4 or 2x converters on my longer lenses, though a friend of mine has put his camera on my gear and got rather better results
Also his camera was less than half the price
Still without t/c's mine is better and I can crop to the equivalent of the 1.4 and get a better image