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09-20-2009, 06:47 AM   #1
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conversion lenses

Hello all out there! Before I purchased my K20D, I used just a digital Olympus camera. I had (and still have) a 1.7x teleconversion lens for it. Is there any thing avaliable out there for Pentax that would be considered a 'conversion lens'? This would be something that I would add to my 55-300 lens to turn it into say a 400 or 500mm lens without actually making the big purchase of a larger lens. I've looked and haven't found anything out there yet. If anyone has any ideas, please let me know! Thanks! ~Donna

09-20-2009, 07:33 AM   #2
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I don't think a teleconverter will work very well with the 55-300mm. You can find info on the TC's here:

PentaxForums.com Third-Party Pentax Lens Review Database - Teleconverters (All Brands)
09-20-2009, 10:58 AM   #3
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And if you search this forum, you'll see lots of people asking more or less the same question - is there a TC (teleconverter) I can use that works well with the 55-300 (or 50-200, or 70-300, or some other relatively inexpensive zoom lens). And the answer is always the same - yes, there *are* TC's available that will turn a 300mm lens into a 450mm lens or a 600mm lens, but the *quality* is generlly worse than simply shooting without the TC and then cropping (ie, the equivalent of "digital zoom"). Plus a TC make you give up one or two f-stops of aperture, making it harder to focus and to get a fast enough shutter speed. TC's are generally designed to work well with more expensive lenses.
09-21-2009, 07:16 AM   #4
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Thanlks Marc, I'll take a look at the site you posted.

09-29-2009, 12:52 PM   #5
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Just talked to a rep at Pentax and he said that no one makes a teleconverter that would work with a Pentax 55-300 SMC DA lens. He said that DA lenses don'e have aperature rings. Can anyone confirm? Any other options for me? Thanks.
09-29-2009, 01:25 PM   #6
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Look, I wouldn't bother using a TC with the 55-300.
AF is grindingly slow and hard to lock focus, and you're just losing far too much light at 300mm.
If it means a lot to you, but money's tight, consider a manual focus mirror lens - 500mm is the common focal length of these lenses.

If you're bent on something AF, I'm afraid these don't come cheap, but if you're going to be taking chances with a TC on the 55-300, then try the Tamron SP Pz-AF MC4 1.4x TC.

I've tried it on the 55-300 and its performance is abysmal. Now on my Tamron 70-200/2.8, it performs absolutely brilliantly. So the 55-300 is not very well suited to having TC's plonked onto it...
09-29-2009, 04:02 PM   #7
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tamron and kenko pictures

If you search the pentax forms for tamron tc converter pics, you will find pictures using tamron 1.4 teleconverter and kenko 1.5 teleconverter or you can double click on the url.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/19694-tamron-t...rter-pics.html
09-30-2009, 09:55 AM   #8
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It is true DA lenses have no aperture rings. It is not true that this means no TC's work with it, if by "work" you mean, physically fits the lens and allows you take a picture with full control over the aperture. But it also remains true that the results will be about the same as if you simply smeared some Vaseline on the front of your 55-300 (to degrade IQ, reduce light and thus force a slower shutter speed, and hamper the AF system), then took the picture, cropped it to give the same field of view as you would have obtained with the TC, and then flushed a $100 bill down the toilet.

09-30-2009, 12:45 PM   #9
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LOL well thanks Marc! that gave me a chuckle. I think I'll keep my money in my pocket.
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