I have been trying to find some comparison reviews of Kenko and Sigma teleconverters against the VERY pricey Nikon. Not having much success.

So, Scoobytogs to the resuce?

Can't find a quality comparison for the Sigma 2X 2.0X APO Teleconverter TC DG (for Nikon).

KENKO Teleplus Pro 300 1.4X 1.4 DG and Pro 300 DG 2.0X 2X for NIKON AFs AF Teleconverter one review stated:
'against the Nikon TC14E II... found no difference in optical performance in digital image 100% view. Price is less than 1/2 of Canon / Nikon. Superb value buy. (... this is not the cheapie MC7 or MC4 series)'

Both Kenkos are approx £50 less (delivered) than the Sigma and more than half the price of the Nikon (Hong Kong , not UK, online shop price comparisons).

Any experience of the Kenko or Sigma teleconverters here?

(NB I have Kenko extension tubes which are v good quality)

I have the Nikon TC14E II which with the 300mmf4 loses you just one stop and no sharpness at all that I can notice. You also keep all the functionality and autofocus etc. That was around about £215 from HK. I have heard the Kenkos are meant to be good for the price but have no experience of them. You start to go to 1.7x and 2x and there will be a more noticeable loss in sharpness.

I have the Kenco 1.4x TC for my Canon, and the main reason I chose this one is that it works with all Lenses

Canon are very particular about which Lenses they will work with, and the same for the Sigma ones, but the Kenko seem to work with any Lens.

The reasons for the above is that the TC Glass is more recessed on the Kenco so doesnt hit the rear element on your Lens, whereby it can on the other makes of TC's

Not sure how this is with the Nikon's though

Thanks for your replies. That's given me some ideas of queries to follow up before taking the plunge and buying.

I seem to remember someone else saying that they'd go for a 1.4 rather than the 2.0 due to loss of sharpness.

I think deano555 the beanbag man uses a Kenko. Maybe drop him a pm.
http://bbs.scoobynet.com/photography-360/639685-camera-bean-bags.html

Thanks for your replies. That's given me some ideas of queries to follow up before taking the plunge and buying.

I seem to remember someone else saying that they'd go for a 1.4 rather than the 2.0 due to loss of sharpness.

I had a Sigma 1.4 for my Canon, which worked pretty, and was about £100 I think. Had to go to part-fund my 70-200, or would have kept it
didn't work with my shorter Canon lenses

Ken Rockwell reckons it's a no-no with my lens (18-200 ).
He advises only using a teleconverter with a lens of at least f/4. The 18-200 is f5.6 at the 200mm end.

Also:

"Mid range zooms like the 18 - 200 VR, 18 - 70, 18 - 55 and 17 - 55 have too much junk in the trunk to allow the [Nikon] TC-20E to fit, even if they were fast enough for it to make sense."

How to use Teleconverters (http://www.kenrockwell.com/nikon/tc.htm)

Maybe I park this idea for a while.

I think he's referring to the 2x version - a 200 f5.6 would become 400 f11, and again there is the problem of whether you can physical fit the lens onto the converter. If the rear element moves and is flush at one end of the zoom range (as opposed to having a resessed area for the converter to sit into) you may find it will fit at one end of the range but strike the rear element as you zoom.

Its certainly the case with the Canon extenders. I'm not familiar with the Kenko converters and the Nikon lens you have.

I certainly find the Canon 2x is not as good optically as the 1.4x, and thats on fixed L prime lenses as well as the 70-200 f2.8L.

You may find in better to save your money and put it towards a good quality fixed 400mm or longer focal length zoom for when you want the extra reach. Bear in mind that a converter on a wide range zoom like your 18-200 is only worth it above the 135mm setting as below that you are still more or less in the zoom range of your original lens, but without the quality or the speed.

Gareth

You may find in better to save your money and put it towards a good quality fixed 400mm or longer focal length zoom for when you want the extra reach.
Yep, that's what I'm now thinking... may be a while yet tho... better start saving

I'm playing with a 70-200/2.8 sigma; never tried the nikon converter; the kenko caused the a/f to go nuts (should allegedly be fine, but wasn't), I have the 2.0 sigma. Theoretically the 1.4 is optically better, but I wanted the reach. It's not noticably crap, but nor have I done a detailed analysis on any image degradation - the images are nice, I'm happy.

I would agree it's not smart on a 5.6 or slower lens:

With the smart t/cs, a/f may well get disabled anyway below a certain f-stop, (kenko will not, it's 'transparent' to the lens / camera in theory at least)

What you will find is even if you can get a decent shutter speed by upping ISO/whatever, the a/f will struggle as it's not got enough light to really work out what's going on.