1.4X Tele Converters: Tamron vs Canon vs Kenko

I have just ordered a Canon EF 70-200mm F/4L IS USM lens from Adorama (Amazon stock availability was on and off, and Adorama also had free shipping like Amazon), and am looking at the possibility of adding a 1.4X Tele Converter to my kit. On the 1.6X FOV crop EOS 400D body I am using, the lens behaves as a 112 - 320 mm F/4 lens, combined with a 1.4X TC, it will become a 157 - 448 mm F/5.6 lens. The intended usage is for candid and wildlife photography.

Note that the 1.4X reduces the maximum aperture by 1 stop whereas the 2X TC reduces it by 2 stops. So the F/4 lens becomes a F/5.6 lens with the 1.4X TC attached. Note also that Canon bodies (other than the professional bodies) cannot autofocus if the max aperture of the lens is smaller than F/5.6. So I will retain AF with 1.4 TC, but not with a 2X TC as that reduces the max aperture of my F/4 lens to F/8.

I researched on the net for the following options:

1. Canon EF 1.4X II
2. Tamron 1.4X AF
3. Tamron SP AF 1.4X Pro
4. Kenko Teleplus PRO 300 DG AF 1.4X
   

Canon EF 1.4X II

• Expensive
• Weather resistant
• Limited to certain lenses (L series mostly) due to construction
  
• Reports correct minimum aperture to camera
• Lowers AF speed to accommodate the TC

Since the 70-200 F4 IS is the only "L" lens I own as of now, the Canon 1.4X would be a bit of overkill for me at this price.

Tamron 1.4X AF

• Cheapest of the lot
• Does not report aperture to body correctly
  
• Black, does not go well with white of L series lens (well that matters a bit!)

Tamron SP AF 1.4X Pro

• Optimized for F/2.8
• Claimed to be identical to Kenko PRO
• White (matches L series)
  

Kenko Teleplus PRO 300 DG AF 1.4X

• Good reviews
• Claimed to be identical to Tamron SP 1.4X
• Cheaper on eBay

The Kenko PRO and Tamron SP are supposed to be identical using glass from Hoya and packaged differently.

Conclusion

After reading all the reviews and comments online, it looks like the Kenko PRO & Tamron SP are good bets over the Canon which is $100 more. I am inclined to pick up the Tamron because 1) I have used Tamron lenses before and like them and 2) it is white and will match my new 70-200 mm f/4L IS and 3) it is said to be optically identical to Kenko 1.4X PRO which has good reviews and 4) it will be useful if I upgrade or buy any F/2.8 lenses in future.

Reviews

• Overview of TCs by Sean
  
• From Bob Atkins, an overview of TCs
• Comparison between Canon 1.4X and Tamron 1.4X on photo.net by Bob Atkins
• A FAQ on teleconverters at Photography-on-the-Net
• Tamron/Kenko compared aginst Nikon in NikonLinks