Update - have now tried the Tamron with tcon attached on a K20D and found it AFs!! So it would appear to be an issue with the newer models only.

The 55-300 is excellent optically - but having used a Nikkor 70-300 AF-s for the past couple of years, it really struggles with action in comparison.

As discussed in the lenses section I recently purchased an as new Kenko 2x to use with my Tamron 70-200mm f2.8 - unfortunately it does not seem to be compatible. I have tried it on my other lenses and it functions on all of them - within the possibilities of slow lenses. On my Sigma non HSM it works perfectly [f2.8/4.5] - on my 55-300 it AFs but very slowly and with much hunting as you would expect on such a slow lens. The good news is that it AFs on my Sigma 55-200mm HSM with little loss of focussing speed - locks focus at f4.5 but as expected hunts at f5.6.
As I no longer have a fast HSM lens or other than the Tamron it seems pointless to keep it.
I paid £75 - open to any reasonable offer! As Sigma don't offer a Tcon that works with HSM in Pentax fit it might make a good cheap alternative!!
Excellent condition, no scratches - more or less as new - both end caps, pouch, box, instructions.

Black K-X and 18-55mm. Purchased new a couple of months ago from someone who had bought it at Argos [unwanted gift!]. Used as back up to my K-5 the shutter count shows under 2000 - see exif data from one of the last times I used it
http://www.flickr.com/photos/greypoint/5752626008/meta/in/set-72157626665700387

Super little camera - no scratches etc. perfect working order - the lens is unused apart from testing to make sure it works. All accessories etc. in original box - battery charger plus two sets of eneloop batteries. £275 plus £10 special delivery UK only

PM if interested

The markings on mine are Pz-AF 2X TELEPLUS MC7 KENKO DG - it sounds like it's a fairly modern design as it has DG on it. It definitely zips along on my HSM lens but the lens is too slow for a 2x and struggles to lock focus. Oh well - I suppose I'd better cut my losses and put it in the classifieds!

Yes - remove the tcon and fit the lens back onto the camera and the af is working perfectly. However, what I've also just discovered is that it is in fact impossible to mf with the tcon on as the focus ring is locked even when set to mf - with the tcon on mf is impossible in all settings and af just whirrs and goes nowhere! Just does'nt seem to like the lens.

OK - had another play although the sun has now disappeared which does'nt help! I gave the Tamron contacts another clean but the result is the same. What I did'nt notice before is that the viewfinder info includes a flashing 'mf' when you try to focus so it definitely does'nt seem to work. I've tried all the various settings AF-S/AF-C/Single and multipoint. Tried the other lenses again and none of them show 'mf' - they all try to focus. Used with the Sigma 17-70 which is f2.8/4.5 it focusses correctly through the range. With the HSM lens the focussing is pretty fast but has difficulty locking focus and hunts slightly - unfortunately I don't have access to an f2.8 HSM lens to see if the extra light would indeed make it focus correctly. Very odd - and annoying as I was caught out a while ago by buying a Sigma tcon which, of course, did'nt af on the HSM lens I then had! Looks like it might be a quick re-sale to someone who has a lens it will work with!!

I have a Tamron 70-200mm f2.8 and just bought a kenko/teleplus 2x MC7 DG to use for the odd bird shot or similar - thinking more record shots than keeping the best quality. Unfortunately it just won't af - tried for a bit but the af just swung to infinity and sits there buzzing. I've tried it on my Sigma 17-70 non HSM where I got focus even at the 70mm end which is not f2.8. Tried with my 55-300mm where it focusses at the short end - just about. And with my 55-200 Sigma HSM where it hunts very quickly but has a job to lock focus - again due to it being a slow lens - but at least it tries to af on all these lenses so does'nt seem to be faulty at all. Anyone used one of these with a Tamron? Tried it on both K-5 and K-x with the same results.

Sold

Purchased February 2011 - so nearly new. Both end caps, hood, padded case - in original box. Fast, silent HSM focussing and a handy range for many.
£375.00 plus £10 special delivery - payment by Paypal preferred. PM if interested [will be listing on ebay in a couple of days - feedback rating is 923 100% positive - see link]




http://feedback.ebay.co.uk/ws/eBayISAPI.dll?ViewFeedback2&userid=greypoint777&ft...