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08-17-2007, 11:23 AM   #1
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Teleconverter 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 50-500lens.

DonR

08-17-2007, 11:27 AM   #2
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lol don't bother with a teleconvter. Quality will be ruined and your aperture will drop to a 12.6 on the long end. You'll be needing a LOT of light to shoot let alone see through your viewfinder.
08-17-2007, 11:54 AM   #3
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QuoteOriginally posted by FotoPete Quote
lol don't bother with a teleconvter. Quality will be ruined and your aperture will drop to a 12.6 on the long end. You'll be needing a LOT of light to shoot let alone see through your viewfinder.
Thanks Pete. That is exactly what I needed to know.
08-17-2007, 12:42 PM   #4
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i agree. you might get by with a 1.4x... i've never liked the IQ of a 2x on any zoom.. too much glass in the way. of course there are combos that will work but the cost is prohibitive.. you may as well buy another lens.

08-17-2007, 01:05 PM   #5
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I've tried my tamron 70-300 with a tamron 1.4x teleconverter. The end result was unremarkable; not bad but not stellar. Also, AF will work (very slowly) in very good light, but predictably it hunts a lot when the light is lower.

I'd recommend cropping to the desired framing to see if you can get the quality of image you're after with the 18-250 as opposed to going with a teleconverter.

I'm very pleased with the quality of the Tamron 1.4, but I prefer not to use it with my zoom.
08-17-2007, 01:09 PM   #6
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A TC will work well in bright daylight with a reasonably fast lens, if the lens has decent image quality. If the lens's image quality is marginal, the TC will just make it worse (garbage in, garbage out).

A 2x TC needs REALLY good input - A sharp lens that is fast. I wouldn't use a 2x with anything slower than an f/4 lens.

A 1.4x TC is a much better compromise. It multiplies aperture by 1.4, i.e. you lose one stop. An f/5.6 lens becomes f/8, which isn't that bad in bright daylight. Unfortunately the 18-250 is slightly slower than 5.6 at its maximum zoom.

There's one problem though - currently the K10D and K100D are not "teleconverter aware" as far as SR goes. If you put a TC onto either, the lens will still report its unmodified focal length to the camera, not the modified one. As a result the camera will undercorrect for camera shake. This will be more significant with a 2x TC than a 1.4x, but my experience is that a Tamron 70-300 lens with a 1.4x TC basically requires additional stabilization even in broad daylight. The Bigma, on the other hand, can (barely) be handheld in daylight from what I've heard.
08-19-2007, 05:47 AM   #7
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How do you think a TC would perform on the upcoming new DA* 300 F4?
08-19-2007, 07:08 AM   #8
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Entropy

When I start up my camera (K100) with a TC in place, I am asked to select the "modified" focal length in order to adjust the SR system properly.

Takes about 3 seconds.

I assume this is also the case with the K10?

08-19-2007, 07:23 AM   #9
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QuoteOriginally posted by Tom Lusk Quote
When I start up my camera (K100) with a TC in place, I am asked to select the "modified" focal length in order to adjust the SR system properly.

Takes about 3 seconds.

I assume this is also the case with the K10?
It works that way my my K10D and a Tokina "Doubler".
With my Vivitar 105/2.5 I just choose 200.
I just checked with my M50/1.7 and still works the same way.

BUT, my TC doesn't have the electrical contacts so I don't know how it works with a TC like the Tamron 1.4 that I think does have the contacts.

Last edited by Eaglerapids; 08-19-2007 at 07:38 AM. Reason: additional info
08-19-2007, 07:53 AM   #10
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QuoteOriginally posted by Tom Lusk Quote
When I start up my camera (K100) with a TC in place, I am asked to select the "modified" focal length in order to adjust the SR system properly.

Takes about 3 seconds.

I assume this is also the case with the K10?
You must either be using an old manual lens or an old teleconverter that does not pass lens information through to the body.

New lens + new TC = body sees lens information (so does not ask for FL), but sees incorrect lens info.
08-19-2007, 06:07 PM   #11
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What brand TC is that Entropy?
08-20-2007, 07:20 AM   #12
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QuoteOriginally posted by Arpe Quote
What brand TC is that Entropy?
Oops, sorry about that. Thought I mentioned.

Same Tamron 1.4x that Andrew Faires mentioned.
08-22-2007, 02:45 AM   #13
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I can confirm many of the points raised here.

For a TC to work, you need to have a very good TC and a fast lens.

I use the Sigma 1.4x that I bought when I bought the 70-200 f2.8 it works very well. Only issue is that Pentax cameras do not modify the focal length with a TC. as a result shake reduction is set to wrong focal length. I have advised pentax of this and requested they give a menu (like the one for manually setting focal length) where we pick a TC ratio.

I also use a 1.7x AF TC which gives a degree of autofocus with manual focus lenses. I use this with an older Vivitar Series 1 70-210 F3.5 and also with a pentax SMC 300 mmF4.0. Results are good with both.

Note anything slower than F4 is really an issue with autofocus working.

Have not tried yet low cost 2x TCs.
08-22-2007, 03:00 AM   #14
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QuoteOriginally posted by Lowell Goudge Quote
I can confirm many of the points raised here.

For a TC to work, you need to have a very good TC and a fast lens.

I use the Sigma 1.4x that I bought when I bought the 70-200 f2.8 it works very well. Only issue is that Pentax cameras do not modify the focal length with a TC. as a result shake reduction is set to wrong focal length. I have advised pentax of this and requested they give a menu (like the one for manually setting focal length) where we pick a TC ratio.
Many have requested this from Pentax (I have), so perhaps it will come in a firmware upgrade one of these days? I would prefer a DA* teleconverter though... One that's weather sealed, has powerzoom contacts for SDM and does the focal length calculation automatically. Preferable a 1.4x and a 2x. Please Pentax....

The Sigma TC I have (the EX2x) doesn't have powerzoom contacts so it doesn't retain SDM, the Tamron 1.4x does have them.

Wim
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