1.7x converter


steve42

Link Posted 02/04/2010 - 13:08
hi all i will soon be looking for a pentax 1.7x converter,ive been trying to find out about lens compatability and how good it is on varying lenses ive just been reading that one chap was using it on a tamron 300mm 2.8 the 60b model he was saying that he was getting purple fringing how bad i dont know ive got the same lens,has any one got any exprience with this combination if so did you have any proplems.
hope this makes sense

steve

whelmed

Link Posted 02/04/2010 - 16:40
There are matched Tamron teleconverters - I'm pondering getting one for my mirror lens. There are also matched Sigma APO ones for the sigma lenses.

While I've never had a Pentax 1.7x converter, I've heard they are pretty epic. They turn manual focus lenses into automatic focus lenses, which is pretty cool. Also, they are often reported as having a very high lens quality. Remember though, a TC will magnify any faults with the lens that you are using it on.

If he wants to get rid of the TC, esp for cheap ... tell him to give me a message
K-5; Siggy 10-20 f4, 30mm f1.4, 18-50mm f2.8, 70-200mm f2.8; Tammy 400mm f4, 500mm f8

whelmed

Link Posted 02/04/2010 - 16:42
http://www.pentaxforums.com/lensreviews/Pentax-Rear-Teleconverter-F-1.7x-Autofoc... shows that most people like them, but someone with some Pentax * lenses isn't happy with the quality.

If you want * quality, ideally you should go for a matched TC. For that Tamron, I'd do the Tamron SP (and only SP) teleconverter: http://www.photographyreview.com/mfr/tamron/35mm-converters/prd_85108_3132crx.as...
K-5; Siggy 10-20 f4, 30mm f1.4, 18-50mm f2.8, 70-200mm f2.8; Tammy 400mm f4, 500mm f8

beginner

Link Posted 02/04/2010 - 16:54
Mine works very well on the DA*300mm,knocks it down to 6.7,but the image quality is still very good!.....I tried it on my Tamron 90mm macro this very morning and it is spot on. You can buy brand new ones on ebay I believe,I dont know where they come from ,as Pentax don't make them anymore......Ken
K20D...ist DS ,DA18/55,DA16/45.DA* 50/135,"A"1.7 50MM..."A" 70/210..M 50mm f2...Tamron 90mm macro,28/300 Tamron,200/500 Tamron 6.9....A Pentax DA*300... Sigma10/20,FA31mm 1.8 Ltd*********,FA 77mm Ltd!

mxds

Link Posted 02/04/2010 - 17:47
Steve
I have a 1.7x which I use on my Tamron 300 2.8, when used with my dS I am more happy with (virtually no CA) but I could never seem to get such good results when used with my K10D donít know why as no one has been able to offer any ideas. I have recently been lucky to obtain a nice used K20 but the weather has been so bad that I have had little opportunity to try this combination out . If you get the chance to buy one do so, mine spends most of the time on the 300 or my 90 2.5 Tamron. If you can find one you wonít be disappointed, trouble is they go for quite a high price nowadays
Mick

steve42

Link Posted 02/04/2010 - 20:14
cheers for info im using the tamron1.4x which is really good just wanted that extra taht the 1.7 could give me. will probably get one seen them for sale on ebay jnfinance has got them trouble is they are 300 quid which i could put towards a k7 cant make my mind up.


cheers steve

pschlute

Link Posted 06/04/2010 - 09:33
I took this shot hand held with the Pentax-F 1.7 converter and my DA* 60-250. The AF and exposure works just great. I need to tell the camera a focal length though for the shake reduction.



Peter



My Flickr page

bforbes

Link Posted 06/04/2010 - 09:48
[quote:3496ace15f="pschlute"]I took this shot hand held with the Pentax-F 1.7 converter and my DA* 60-250. The AF and exposure works just great. I need to tell the camera a focal length though for the shake reduction.
/quote] When you set the focal length do you use the max. of the zoom range, or reset it as required for each shot. If you see what I mean.
Barrie
Too Old To Die Young

http://www.pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/

pschlute

Link Posted 06/04/2010 - 10:03
Barrie

ideally one should set it each time to the focal length you are using for the shot (in this case multiplied by 1.7 because of the t/c).

In practice that is a bit of a chore so I set it to the lower end of the range i expected to use. I anticipated using the 200-250 range for shots of the Pheasant so allowing for the t/c I entered 350 as my S/R focal length. If you are going to miss on the input length it is best to be on the low side as a longer input focal length will cause the camera to overcompensate and actually induce shake.
Peter



My Flickr page

bforbes

Link Posted 06/04/2010 - 10:10
pschlute wrote:
If you are going to miss on the input length it is best to be on the low side as a longer input focal length will cause the camera to overcompensate and actually induce shake.

Thats interesting, I've been trying a Sigma 170-500 with a 1.7TC, and not been happy with the results. My instinct was to set it for worst case scenario, ie. 1.7x500, maybe I was wrong
Barrie
Too Old To Die Young

http://www.pentaxphotogallery.com/artists/barrieforbes
https://www.flickr.com/photos/189482630@N03/
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