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09-23-2014, 06:37 PM   #1
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new 1.4 teleconverter

after reading the PENTAX review on the new 1.4 teleconverter it was not recommended for use with 70-300 consumer zoom which I had recently purchased
why is that and what is suggested in lieu on using a Pentax converter?

09-23-2014, 07:51 PM   #2
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All TCs work better with fast lenses because you lose some stops. The 70-300 is not fast enough. It may work in bright days though.

https://www.pentaxforums.com/articles/photo-articles/k-mount-teleconverter-guide.html
09-23-2014, 08:03 PM   #3
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Good question which leads me to another one:

Would this TC work with the DA 55-300 ?
I "almost" let my son use my converter (that same new HD 1.4x) on that lens of his but saw that the elements were moving while zooming .... wouldn't that cause the teleconverter and the lens components to "knock" against one another ?
09-23-2014, 08:21 PM   #4
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QuoteOriginally posted by jpzk Quote
Good question which leads me to another one:

Would this TC work with the DA 55-300 ?
I "almost" let my son use my converter (that same new HD 1.4x) on that lens of his but saw that the elements were moving while zooming .... wouldn't that cause the teleconverter and the lens components to "knock" against one another ?
There is a list:
http://c758710.r10.cf2.rackcdn.com/files/support/manual/1394730000_DA_Rear_c...lity_Chart.pdf

The 55-300 is explicitly listed as compatible, although autofocus may not work toward the long end unless you have a ton of light. Usually, minimum aperture f/8 is the absolute best you can hope for in phase detection autofocus systems, and 1.4 x 5.8 = 8.12 is right at the limit. At the short end, it should still be ok. At max focal length, you will do best to switch to live view. That should work.

09-23-2014, 08:42 PM   #5
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My 55-300 works with the Tamron 1.4x. So does the 18-135 WR but you need good light. The rear elements do not protrude too much so I do not think there should be a problem.
09-23-2014, 09:04 PM   #6
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QuoteOriginally posted by jpzk Quote
Would this TC work with the DA 55-300 ?
The AF won't work in the range of 135mm to 300mm because the lens become about f/5.6 thus with addition of the TC it will be an f/8 lens (One stop light loss) So only in very bright daylight the AF may work! or may not work at all! And the Viewfinder will be dim for manual focusing too.
09-23-2014, 09:07 PM   #7
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The HD DA 1.4x Rear Converter is designed to work optimally with lenses with a widest aperture of f/4.0 or faster.

It will work with the DA55-300, just not optimally. Certainly, no damage will be done.
09-23-2014, 11:42 PM   #8
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I have da55-300 + tc1,4 combo in use. It works but it really isn't the best pair. At the long end the IQ and focus performance will drop significantly.

That's the reason why I'am currently waiting for a da*300 to be delivered...


Last edited by Hemppo; 09-24-2014 at 01:23 AM.
09-24-2014, 10:15 AM   #9
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Did someone test the TC 1.4 converter with a SMC F* 4.5 300?
09-24-2014, 10:19 AM   #10
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The 55-300 works fine with a Vivitar Series 1 1.4x.
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