Is it pointless to buy a 1.4x teleconverter for 400mm f/5.6 lens?

Since I will lose an f stop and autofocus, I'm wondering if I'm wasting my money in buying the Kenko Teleplus PRO 300 DGX 1.4x AF Teleconverter for my 400mm f/5.6 lens? I can shoot in bright light if that makes a difference. I would like the added reach but not at the cost of IQ. Talk me into it our out of it! Thanks.

You can tape some of the pins on the Kenko 1.4x so you don't lose autofocus, if that helps sway you one way or other.

When you use a teleconverter you'll always lose IQ, that's nothing new. I can say that I have the Canon 1.4 extender and occasionally use it with my 400mm 5.6. I'm usually surprised with how good the results are.

Considering what you're going to have to pay for more reach, it might be worth it, particularly the II rather than the III.

I don't have the 400 5.6, but it is very likely that you will do better by using the 1.4x than cropping.

You will probably also be able to use contrast-detect focusing if that helps (it's what I do with the 70-200 f4 + 2xTC). It does OK if the subject is not moving much (slow, but accurate still).

cdo221 wrote in post #14275682
You can tape some of the pins on the Kenko 1.4x so you don't lose autofocus, if that helps sway you one way or other.

I did this. AF worked 90% of the time in outside lighting, and results were better then they had any right to be considering the "workaround" of taping pins etc. Not bad at all for 560mm.

I would definitely go for it. As ejenner noted, any other option for more reach will cost you over a $1000(Sigma 150-500OS) or the next-cheapest route being a 300L f/2.8 with 2x TC. You can also use the TC on your macro lens, if you want.. i often use the 1.4x on mine. Gives you 1.4:1 mag.

I have used the 1.4x II on my 100-400L with good results, and the prime should be better than that. I don't bother trying to fool the camera, just focus manually. I guess it depends on the subject and lighting.

I use the Kenko 1.4 on my 100-400 at all times. Autofocus is fine - no pin taping. Results are sharp enough for me. Here is a recent example.

http://www.flickr.com …6937411020/in/p​hotostream

At 560mm depth of field is pretty narrow even at f8.

Auto focus works fine on my 400 F5.6 with the Kenko 1.4 300DGX without any taping.
Here is a pic at F8.0. This shot was hand held. Always nice to have the 1.4 in the bag when you need it.

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Thanks, everyone, for your replies. I think I'll take the plunge on the Kenko since it's a decent price.

i have the Canon 1.4 III and the Canon 400mm f/5.6. here's my thoughts. IQ is slightly "degraded", no doubt, but its still very good, and its a grittier kind of quality. it's quite nice, actually.

i can't speak for the Kenko, but i always read/hear that the Canon 1.4x II is as good, and much cheaper than the version III i splurged on.

the upside is, that you get shots you wouldn't be able to get. AF is also not affected. couple of samples:

Other than shooting the Moon I rarely use my 400 5.6 with a TC but I did get one OK shot with it once. Little soft but I found it difficult to hit focus on the 7D manually.

IMAGE LINK: http://www.flickr.com/​photos/cheising/633885​5709/

Ive used my Kenko 1.4 MC4 DGX on my 100-400 before.
The results are pretty close to what I get when I just crop it, so I threw it in my camera bag and it has sat there for a few months.
I think on a prime it would be better, but the decrease or loss of AF isnt worth it to me.