Please advise which 1.4x teleconverter to buy: Kenko, Tamron, or Sigma

[Vivid Color]

I have both the Canon 6D and the T1i and I recently bought the 70-300L for an upcoming African photo safari. My question is: should I buy a teleconverter and, if so, should I buy the Kenko 1.4 TC or some other non-Canon brand?  I know that there are other TCs on the market, such as Tamron's and Sigma's, yet I haven't been able to find much in direct comparisons to the Kenko. The comparisons generally seem to be between the 3rd party and Canon, which isn't helpful since the Canon TC won't work at all focal lengths on the 70-300L and therefore, I do not wish to buy it. (By the way, I posted a version of this question earlier, but did not receive any replies so I'm reposting it. I've also revised the subject as I realized the prior subject heading I used earlier today may have led you to think I was trying to start a theoretical debate when I'm really asking for your practical advice on what, if any, teleconverter I should buy.) Your comments about the various non-Canon brands of teleconverters and which might be best (if such a statement can even be made) will be greatly appreciated.

[wickidwombat]

I have the kenko 1.4TC DXG300 its a good little unit and comparable to the much more expensive canon version with the added benefit that you can use it on other lenses its a great addition to a 100mm Macro lens for example.

[Mt Spokane Photography]

Tamron TC's are mad by Kenko, but might not have the same electronics, but glass is the same.
So you are down to Sigma, Kenko, or Canon.
Do you have or need weather sealing?  Canon is the only one.  Otherwise, I'd go with Kenko.  I did buy and return a Kenko 1.4X TC, it locks up a 5D MK III with certain lenses, most noticably the 100mm L.  It only seems to do this with the MK III, I have no info about a 6D.
 
There is always the possibility that a TC will fail to be compatible with a future camera model, so factor that in as well.  There are a ton of older third party TC's that are not (fully compatible with newer cameras, meaning that they do not report information correctly, or do not work with certain lenses)

[wickidwombat]

I did buy and return a Kenko 1.4X TC, it locks up a 5D MK III with certain lenses, most noticably the 100mm L.   

strange my first mk3 (the one i had problems with did this, but its fine on the new body I'll have to test it out on the body i just bought  and see if there is anything there)

[J.R.]

I did buy and return a Kenko 1.4X TC, it locks up a 5D MK III with certain lenses, most noticably the 100mm L.   

strange my first mk3 (the one i had problems with did this, but its fine on the new body I'll have to test it out on the body i just bought  and see if there is anything there)

Please let me know your thoughts on this. I would be interested in this because I was planning to get a 1.4x kenko for using with the 5d3. I've heard that the kenko 1.4x somehow overrides the f/8 limitation for AF on the 5d3 while being cheaper.

[J.R.]

Tamron TC's are mad by Kenko, but might not have the same electronics, but glass is the same.
So you are down to Sigma, Kenko, or Canon.
Do you have or need weather sealing?  Canon is the only one.  Otherwise, I'd go with Kenko.  I did buy and return a Kenko 1.4X TC, it locks up a 5D MK III with certain lenses, most noticably the 100mm L.  It only seems to do this with the MK III, I have no info about a 6D.
 
There is always the possibility that a TC will fail to be compatible with a future camera model, so factor that in as well.  There are a ton of older third party TC's that are not (fully compatible with newer cameras, meaning that they do not report information correctly, or do not work with certain lenses)

Thanks ... Which other lenses were affected?

[Vivid Color]

Thank you to all who have replied to my question about whether I should buy a Kenko, Tamron, or Sigma 1.4x teleconverter to use with my 70-300L lens on either my 6D or T1i. Your information is quite helpful regarding the Kenko and Tamron teleconverters.

Has anyone used a Sigma TC?

[TexinAfrica]

I have the Canon 70-300 L and I have a Kenko 1.4 TC tele-pro - and I've been to Kenya the past two August's for the Great Migration.  I'm going again this year as well.  The Kenko works very well.  During the day on the Masai Mara you generarally have lots of light.   This due to the 6000' elevation, most days are very clear.   Only in the very early morning or late afternoon would I notice the lens 'searching' for focus.  I'm not anywhere near as advanced as some of these participants, but when I had the normal day's light, I could see no drop off on focus speed.  Hope this helps.  FYI -- try and stay nearby or within an hours drive of the Mara River in the Masai. That's the best action is during the Migration. 

Also, I've decided I will sell my 70-300 and move up to the 100-400L.  Just want a bit more reach.  Having said that, I used a Sigma 12-24 for many situations and had as many great pics with it as with the tele's.

[Vivid Color]

Thank you, TexinAfrica, for letting me know about your experience with the Kenko 1.4x teleconverter in Kenya. I think I will try to test out the Kenko. I'll be going on the northern circuit of national parks in Tanzania this August -- my first trip to Africa -- I can't wait! As for the 100-400L, I originally thought about getting that lens, but when I tried it out, It was just too long and heavy for me -- I couldn't hold it steady enough to get clear, sharp shots and even it's IS wasn't enough. But, I have no problem with the 70-300L, which is why I bought it. (The CR review of it was quite helpful in my decisionmaking.) Hopefully, adding a Kenko TC to my 70-300 won't throw off the ergonomics. I'll try it too before I buy it. And, your point about a wide-angle lens is noted. I don't have an ultra-wide (that and/or a macro lens is on next year's wish list), but I am planning to take my 24-105L for the 6D and maybe my 18-270 Tamron as a backup lens for the T1i.