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08-17-2007, 11:16 AM   #1
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1.4x or 2.0x Teleconverters with Zoom Lenses

I'm new here and was wondering if anyone has uses a 1.4X or 2.0X Teleconverter lenses on Zoom Lenses and how the work quality wise. I'm thinking of the new Tamron 18-250 f2.5-6.3 lens with one or the other telerconverter lenses on the K10D. I know it would be manual focus with it on but the reach would be nice and it would be way lighter than the Sigma 50-500 lens.

DonR

I just realized I posted this in the wrong place. I'll repost it on the Lens discussion.

08-17-2007, 01:28 PM   #2
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Well, I'll offer up this as an opinion.. Just my .02

Teleconverters do a couple of things.. One, they multiply your focal length. So, if you have a 2x teleconverter and a 200mm lens, you will then have a 400mm lens.. Some other things they do while extending your focal length would be, they stop down your aperature. So, if the 200mm lens is a f5.6, expect it to be f11.2 with that teleconverter attached. Still, that isn't so bad, until that is, you try to take a shot. You're not going to be hand-holding a 400mm f11.2 with a shutter of, maybe 1/125? Of course it all depends on the shot but, fast moving objects could be a real bitch to capture.. Tripod mounting would be best. And your autofocus is likely to not work so well. Also, you could lose some sharpness in the photo, though, this is subjective and relative to what you're after in a final image. I mean, what's the point in griping about a loss of sharpness when you wouldn't have had the shot in the first place without the teleconverter? Get what I mean? Also, higher quality tele's should yield higher quality images.

How would I do it? I'd buy a 300mm f2.8 and a 1.4x teleconverter. This would give me 420mm of reach at a fast f4. OK, even if you went with a 1.7x teleconverter you'd have about f5 @ 510mm.. Or, possibly the 2.0x teleconverter giving you 600mm @ f6..

The key to teleconverters are in the lenses themselves. For best results you need a fast fixed focal length lens with sharp optics.
08-17-2007, 02:09 PM   #3
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I would comment but Tom stole all the best points. You can also search on this many posts on teleconvertors
08-17-2007, 02:40 PM   #4
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to tell you the truth, i've never been happy with a 2x on a zoom lens. IQ just suffers too much. i'm sure that some of the really high end TCs and high end zooms may work but by the time you get this setup you may have exceded the cost of two separate lenses. just my 2..
i have less problems with the 1.4s. but my pentax 1.4x-s cost me $130 which is more than many of the lenses i have and use.

08-17-2007, 03:01 PM   #5
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Roy: does AF still work w/ the Pentax 1.4x-s? E.g., if I stick it on my Tamron 70-300, do I lose AF? I know you won't w/ the Tamron 1.4x convertor but I wanted to know if the Pentax works and whether the 1.4x-s passes through the zoom contact so it'll also work w/ SDM lenses...
08-17-2007, 03:33 PM   #6
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no AF because it's an A lens. AF was never supported.
i've got a tamron 2x mc4 that is AF but it doesn't work with the kit lens and it's the only AF lens i have. the problem is that the AF needs a certain amount of light to work..
08-17-2007, 03:40 PM   #7
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grrr...cheap small MF 300/2.8 prime need I :-P

Hitting the US Open (tennis) in a few weeks and trying to figure out how to get a bit more reach and it doesn't look like teleconvertors will work that well unless tied to a 300/2.8 prime, which of course isn't allowed because it's a "pro-size" lens (dumb "security" rules). It's one of few those days when I'll regret not getting a Canon because they have so much fast glass available (and OEM good quality teleconvertors that are still sold)...
08-17-2007, 04:51 PM   #8
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QuoteOriginally posted by d-sr Quote
I'm new here and was wondering if anyone has uses a 1.4X or 2.0X Teleconverter lenses on Zoom Lenses and how the work quality wise. I'm thinking of the new Tamron 18-250 f2.5-6.3 lens with one or the other telerconverter lenses on the K10D. I know it would be manual focus with it on but the reach would be nice and it would be way lighter than the Sigma 50-500 lens.
Teleconverters can work well on certain zoom lenses. If the lens is fairly fast (f/2.8-4), has very high image quality, and the lens and converter are matched to work together, then the results can be good. For example, I have a Sigma APO 100-300mm f/4 EX DG and the matched Sigma APO 1.4X EX DG converter, and the image quality is quite good at 420mm, especially stopped down a bit. Other examples would be top quality 70-200mm f2.8 lenses with matched converters, like the Canon, Nikon or Sigma lenses.

In your case, the is Tamron 18-250 f2.5-6.3 is a a nearly 14X zoom. While it is quite an engineering feat to create such a lens, the image quality on the long end is not the best. Plus, it is is a super-slow f6.3. Plus, there is no matched converter. So I wouldn't expect good results from this lens with any teleconverter.

08-17-2007, 04:57 PM   #9
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QuoteOriginally posted by GaryML Quote
Teleconverters can work well on certain zoom lenses. If the lens is fairly fast (f/2.8-4), has very high image quality, and the lens and converter are matched to work together, then the results can be good. For example, I have a Sigma APO 100-300mm f/4 EX DG and the matched Sigma APO 1.4X EX DG converter, and the image quality is quite good at 420mm, especially stopped down a bit. Other examples would be top quality 70-200mm f2.8 lenses with matched converters, like the Canon, Nikon or Sigma lenses.

In your case, the is Tamron 18-250 f2.5-6.3 is a a nearly 14X zoom. While it is quite an engineering feat to create such a lens, the image quality on the long end is not the best. Plus, it is is a super-slow f6.3. Plus, there is no matched converter. So I wouldn't expect good results from this lens with any teleconverter.
that's why i mentioned , high end... how much did your kit cost ??
$1100 ????
08-17-2007, 07:42 PM   #10
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I have had good results using several different TCs, including the sigma 1.4x on my F2.8 70-200mm sigma AF zoom, and the 1.7x AF adaptor from pentax, on a manual focus SMC 300mm F4,

The only issue I have is that the pentax cameras do not seem to have any focal length compensation in either the EXIF data and in the setting of focal length for shake reduction, and as a result the true focal length is not recorded or used. this makes shake reduction sub optimal because it is set for the wrong focal length
08-20-2007, 08:10 AM   #11
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Lowell, The Pentax K10D DOES have focal length compensation.

The minute you slap a teleconverter and lens on the K10D it will ask you what focal length you're using. Once you tell it the proper focal length, your EXIF data will be correct and the shake reduction will compensate as well.
08-20-2007, 10:53 AM   #12
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QuoteOriginally posted by Tom M Quote
Lowell, The Pentax K10D DOES have focal length compensation.

The minute you slap a teleconverter and lens on the K10D it will ask you what focal length you're using. Once you tell it the proper focal length, your EXIF data will be correct and the shake reduction will compensate as well.
This only works if you have a non automatic apature TC and/or non automatic apature lenses.

I have a sigma 70-200 F 2.8 and the K10D shows 200mm flcal lentgh when the 1.4 x TC is attached.

Same if I mount that TC on any other lens, no change in focal length.

Using an old Takamar TC with electronc contacts I agree you get prompted for focal length. but not wth newer TCs or with the 1.7x AF TC they just report directly the lens focal length without correction and there is no prompting for focal length.

Prompt for focal length only happens when none is reported back from lens. if the lens reports it back to the camera, you can't adjust it for the TC factor/ This has been reported to pentax and forwarded to thier R&D group
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