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Old Feb 4, 2007, 12:46 PM   #1
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I was looking for a cheap teleconverter to extend my Pentax 100-300mm lens. That lens is not really a high quality lens but a decent quality lens that I bought for about $70 used. I wanted to extand the focal lenth to it. I saw a few Vivitar 2x AF teleconverter on ebay for a good price, about $30 shipped for it.

Has anyone had any experiance with it or have it right now?
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Old Feb 4, 2007, 3:53 PM   #2
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I have a Vivitar 2x Macro teleconverter that I've used for macros and was pretty happy with the results. I haven't used it much on my longer lenses so I couldn't say how that might work out (though I intend to try once the weather warms up). From what I've heard, using a 2x tele on a lens that long may hurt the quality noticeably, whereas something like a 1.4x or 1.5x wouldn't be so bad.

The real problem though is that a 2x tele will cut the light input in half so that you'd need to use slower shutter speeds, which can be a problem at really long telephoto. It hurts the wide angle more since you're losing brightness and sharpness on shots that you could have gotten without the teleconverter.

However, if what you really want is a 600mm focal length, and you think you can deal with using shutter speeds that area half as fast as what you use at 300mm, then it's got to be the cheapest and most portable way of doing it, though I suspect you'd get somewhat better results if you did it with a 300mm prime.
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Old Feb 4, 2007, 8:34 PM   #3
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Thanks. Well I won the bid on the Vivitar 2x AF teleconverter about $20 shipped but the dead beat seller won't contact me and its been over a week since I won the bid. I will have to take it with paypal and ebay to get my money back. Well today I just won another bid for the same teleconverter but from someone else for about $14 shipped. I just hope that it would be worth that $14 and I hope that I will get it this time.

The teleconverter will be used for taking picture of birds with my Pentax 100-300mm lens. I don't mind loosing some light and at the time I don't have the money to spend on a high quality telephoto lens.
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Old Feb 5, 2007, 11:37 AM   #4
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Hi Superakuma,

I hope that you'll be getting something that you can use, but I'm afraid that you'll find that the AF doesn't work (not enough light), and it will probably be difficult to focus manually at f11 effective aperture. Of course I could be wrong -- keep us posted on how well this works when you get the TC.

Scott
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Old Feb 5, 2007, 5:51 PM   #5
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i've never had much luck with a 2x on a zoom. hope it works well for you.

roy
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Old Feb 5, 2007, 6:30 PM   #6
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What brand was that 2x that you had? I wish I would of posted this before I hit the bid button on ebay. But it is only $14, might as well worth the try.
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Old Feb 5, 2007, 9:50 PM   #7
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I have recently acquired a Vivitar 2x.Mine will not autofocus and it has to be really bright to get a good shot. I got it cheap like you so it is not a big deal to me. It is just something to play with. I have learned that it has to be really bright to use effectively it at full 200mm.
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Old Feb 5, 2007, 9:54 PM   #8
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Superkuma For that price no great loss....

I've never cared for Vivitar anything all that much.

But not satisfactory you could always do this...
http://www.stevesforums.com/forums/v...mp;forum_id=80

And end up with an AF extention tube.

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Old Feb 6, 2007, 12:30 AM   #9
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Hi Hayward,

I wouldn't be too quick to write off Vivitar as a lensmaker, though they are a mere shadow of what they were quite a while ago.

Their 70-210 f2.8-4 Series 1 (made by Komine) are still highly regarded and actually sought after, as are their Series 1 Solid Cats. The 100 (or is it the 105?) macro is very good as is the 2x Macro Focusing Teleconverter (which I actually own). This last piece, the 2x MFTC, not only doubles the effective FL, but also allows any lens to focus contimuously from infinity all the way down to 1:1 with very high quality results. . . not quite as good as an OEM dedicated macro, but surprisingly close, and that's really good-- it's also a competent manual focus 2x TC, tho I have little use for one.

While most of their current stuff leaves a bit to be desired, Pentax DSLRs' ability to use these old lenses open up a world of possibilities not available to owners of other mfg's DSLRs. A lot of lens mfgs in the past were downgraded for excessive edge softness and distortion -- but that was for full frame 35mm. The 24x16 sensor on our Pentax DSLRs cut away the sometimes offending edges, and some mediocre cheap lenses become hidden digital jewels. This is an area where we have all the fun (if you're into that kind of thing)

The other mfgs' owners might have the "advantage" of being able to walk into any dealer and lay down some significant cash for brand new lenses, but we can walk into a pawnshop or Good Will outlet with $10 in our pocket, and possibly walk out with a great performing lens that nobody's ever heard of. Of course, this doesn't apply to every lens, but I've often been surprised to see great pics posted that were taken with lenses that from reputation I wouldn't have accepted if they were offered to me for free. Backward lens compatibility makes you look at things differently.

Scott
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Old Feb 6, 2007, 3:22 PM   #10
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snostorm wrote:
Quote:
This last piece, the 2x MFTC, not only doubles the effective FL, but also allows any lens to focus contimuously from infinity all the way down to 1:1 with very high quality results. . . not quite as good as an OEM dedicated macro, but surprisingly close, and that's really good-- it's also a competent manual focus 2x TC, tho I have little use for one.
Hey, that's the teleconverter I've got! I've really enjoyed using it so far and thought that the images I've gotten were a lot sharper than people seemed to suggest I should be getting from a 2x. I'm just a bit disappointed that it doesn't work properly with the kit lens. With a 50mm prime it can completely fill the frame with a dime (actually, a dime is a bit too big...). The kit lens can get a lot closer, but it will only shoot with the smallest aperture or the widest.

You think $25 was a good price on this thing?
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