1:4 converter with is100- 400 & 10D

[roypotter]

Hi,
I'm currently using a 10d with the 1-400is lens but want to add a converter.
I'm pretty sure I won't go for a x2 as I believe I'll loose too much light / quality but I'm unsure as to what make of converter to go for & which ones will work with with my kit.
The obvious choice would be the canon 1:4 but is it really worth the extra money over say a Kenko or a sigma and will these converters work the same with my set up as a canon one would?
Also i'm aware of the taping trick to get autofocus on the canon but am confused as to the varied results posted, some find the autofocus slow, some say its ok ? Will I have to do this to get full auto focus on my set up ?

Any thoughts or experiences on converters with this set up much appreciated

cheers

Roy

[formula4speed]

You won't see a noticeable difference between a good third party converter like a Sigma EX series and a Canon teleconverter. There are only 2 reasons to go with the Canon that I can think of, 1 is you need weather sealing but your body isn't weather sealed and I don't think the 100-400 is either so scratch that. Second is if you are a canon purist and only use canon products, since you are asking I'm guessing you are not one of these people. Save some cash, go third party. The tape trick is the only way your camera will autofocus with a converter since your max aperature becomes f/8, how well your camera will focus with the tape trick will vary depending on conditions. Mainly the amount of light entering the lens and the amount of contrast on your subject.

[John Gibson2]

What is the tape trick? I know that it entails taping over some contacts, but which ones, and is there any risk to the camera/lens?
John Gibson

[compa]

What is the tape trick? I know that it entails taping over some contacts, but which ones, and is there any risk to the camera/lens?
John Gibson

With the converter in hand:

looking at the end of the converter that attaches to the lens
rotate it so the contacts are at the top
the leftmost 3 contacts are the ones to tape over
for reference, the rightmost 3 contacts are on a raised area

What you end up with is that the converter basically becomes invisible to the camera. The camera still receives most info from the lens and therefore the EXIF will have the focal length of the lens alone (without the extender's multiplication factor). It also means that the camera will not realize that the stuff hanging off the front is worse than the f/5.6 cutoff point for autofocus.

But, unless you are shooting in very good light at high contrast subjects, you will usually get a lot of seeking and frequently it simply will not focus. But it does work!

As far as damage to the camera/lens/converter - no chance that I know of unless perhaps there are some nasty chemicals in the tape you use to cover the contacts.

[cfagyal]

The tape trick generally isn't worth bothering with in my opinion, as like Jim said, it will seek/hunt A LOT and even when it does auto focus it will be slow as dirt. To give you an example of slow...and this should really put this in perspective: The Canon 1dMkII Autofocuses with anything to f/8 or less. With my 400mm f/5.6L and a 1.4x TC giving me 560mm@f/8, the MkII autofocuses without taping..it was so incredibly sluggish and slow that I never bothered with trying to autofocus with that combination again, because it was a waste of time and an exercise in frustration. The MkII is the fastest focusing camera in Canons lineup...given that...you can imagine why I recommend against even bothering with trying to tape pins to fool a 10D into autofocusing at f/8 or what not.

Secondly, I wouldn't even use a TC with the 100-400 which has sharpness problems to begin with. Adding a teleconverter to it just wouldn't produce very many quality images in my opinion. I'm generally dissatisfied with images from my 70-200 f/2.8L USM (which is the sharpest zoom lens in Canons lineup) when I add a teleconverter.

Just one persons opinion,
Cheers,