I agree Roy,they dont work well on all lenses but I have had some cracking pics with both my ef 75-300 and my sigma 135-400.The attached pics were taken with the sigma and the kenko pro 1.4x TC.The redstart is quite a heavy crop and needed some work in photoshop as it was overexposed by 1 stop (dont ask!) and was washed out.I have a few examples when using the 75-300 and the cheaper kenko 1.5x TC on my birdforum gallery.I would have downloaded some off there and attached them here but it is offline at the moment.

Thanks, guys. I'll be careful but if I could get shots like John's with a tc I'd be delighted.

Nice shots, Mike. I'll be in Ontario this summer and will be talking to the folks at Henry's (a leading Canadian camera shop). They have a good reputation and hopefully will steer me right. The toughest thing will be convincing my wife.

Managed to dig out the gull shot from my birdforum gallery.This was taken on my 300d with my ef 75-300mm and the cheaper kenko 1.5x converter.

I just ordered a Kenko 1.4 Pro 300 to use with my manual focus Nikkor 400 IFED AIS f5.6 lens. I will post some test results when I get it.

Don

This shot was taken today using a Canon1x4 with the 100-400.I had messed up the lens on my 400F5.6 trying to clean it,and made it very smeary,so had to use the 100-400 with the 1x4 attached,too windy to remove.Considering I was shooting directly into the sun,and not holding the cam very steady,not bad.Bird is a Meadow Pipit.

Nice one Christine - still plenty of detail in the bird. Hope you can clean your 400mm prime ok.

A lovely sharp photo Christine. I do hope its only a smear and can be cleaned off.

Well done Christine nicely exposed and good contrast for against the light. Sorry about your lens smear. I hope there is no permanent damage. I am not using my Canon 400 mm f5.6 as much as I expected to mainly because often, I unexpectedly need to shoot closer than 11.5 feet.

Thankyou for the comments and concern,have not had time to check the lens,I spit on the cleaning cloth to remove a stubborn smudge and the heat of the sun dried everything too quickly,so I am trying to think how to clean it properly.Maybe some sensor cleaning fluid may work-----but,I cannot be too bad,'cos I took this shot this afternoon outside my back door,and apart from removing the dust spots.no other editing needed.but I will have a try tommorrow,as it is very smeary.