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04-09-2007, 08:52 PM   #1
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extension tube vs teleconverter

I am not sure I understand the technical difference between extension tubes and teleconverters. I have a 1.4x Tamron teleconverter that I use with my 70-300mm zoom lens. What difference would an extension tube make, if any?

Will

04-09-2007, 09:00 PM   #2
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QuoteOriginally posted by WMBP Quote
I am not sure I understand the technical difference between extension tubes and teleconverters. I have a 1.4x Tamron teleconverter that I use with my 70-300mm zoom lens. What difference would an extension tube make, if any?

Will
Teleconverters increase the effective focal length of the lens and contain lens elements to achieve this.

Extension tubes are exactly that: devices for positioning the lens further from the sensor to enable closer focussing. The have no lenticular elements.

There have been a few variations on the theme. I recall one, by Tamron I think, which was a teleconverter with a removable lens element group which left the empty body to be used as an extension ring.

HTH
04-09-2007, 09:05 PM   #3
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QuoteOriginally posted by Rolly Quote
Teleconverters increase the effective focal length of the lens and contain lens elements to achieve this.

Extension tubes are exactly that: devices for positioning the lens further from the sensor to enable closer focussing. The have no lenticular elements.
Thanks, Rolly, for the quick response!

So, are extension tubes useful only for macro or close-up photography? Somewhere I got the impression they could be useful for shooting at a distance, too - say, for shooting birds or people on the other side of the street. Am I mistaken about that?

Will
04-09-2007, 09:11 PM   #4
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Correct, Will.

The 'tubes' are one of the devices for increasing the lens-to-sensor distance. There are extension bellows which do a similar job, but with greater variability, and, of course, all the "old" studio cameras with their bellows construction had it 'built-in'.

04-10-2007, 07:23 AM   #5
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QuoteOriginally posted by WMBP Quote
Thanks, Rolly, for the quick response!

So, are extension tubes useful only for macro or close-up photography? Somewhere I got the impression they could be useful for shooting at a distance, too - say, for shooting birds or people on the other side of the street. Am I mistaken about that?

Will
will,
they can be advantageous when shooting birds with a long lens. i've never tried but have seen results. my 500mm has a close focus of about 10meters, 33 feet. putting an ET on it would allow me to focus closer than that. altho i'd lose infinity focus. i plan on trying it if i ever get the back from the shop.
04-10-2007, 07:54 AM   #6
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QuoteOriginally posted by WMBP Quote
I am not sure I understand the technical difference between extension tubes and teleconverters. I have a 1.4x Tamron teleconverter that I use with my 70-300mm zoom lens. What difference would an extension tube make, if any?

Will
Hi Will,
An extension tube is pretty much a one trick pony. It gives you the ability to focus closer. It's only use AFAIK, is in macro photography.
A TC can do the above but it's primary function is to increase the magnifying power of the lens. Like Rolly has said the ET is just that a basically empty tube, (tho with contacts so that your automatic lenses still stay auto) while a TC has lenses.

NaCl(but you can use a TC as an extension tube but not vise versa)H2O
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