telextenders vs. extension tubes

[brian_keyashian]

What's the difference between canon's 1.4x and 2x telextenders and their

extension tubes? It seems like they both do the same thing, ie let you zoom in

farther. I had thought that extension tubes were for macro work, but kenko's

website shows pictures of a mountain with different extension tubes. (link:

http://www.thkphoto.com/products/kenko/slrc-04.html )

 

Thanks,

Brian

[richard_cochran]

Extension tubes have no optics inside them. They're just hollow tubes that move the lens further away from the film (or sensor) plane.

<p>

As written in that link you posted, <cite>When using extension tubes the lens will not focus to infinity. The focus range will be greatly limited to a very close focusing distance. </cite>

<p>

Those sample photos of a mountain from that link were not taken using extension tubes. They're either bald-faced blatant lies or else they're intended to represent photographs <em> of a photograph of a mountain</em>, in which case they're still pretty misleading.

<p>

Telextenders, on the other hand, don't alter focusing distance, but do alter focal length, and thereby alter field of view. Telextenders do have optical elements inside.

[Michael R Freeman]

The Kenko site is misleading, as extension tubes will NOT allow you to get closer views of a mountain.

 

Extension tubes allow you to focus closer, which gives a higher reproduction ratio, but infinity focus is lost.

 

Extenders (teleconverters) increase image size (and hence reproduction ratio), but do NOT allow you to focus closer. As an example, if your lens will focus to 1:4 without accessories, a 2X extender will allow you to achieve a 1:2 reproduction ratio from the SAME distance. Extenders also allow you to retain infinity focus.

 

Both teleconverters and extension tubes will cost you light, and result in smaller effective apertures. While the amount of light lost is constant for teleconverters (1 stop for 1.4X and 2 stops for 2X), the effect of extension tubes is dependent on the focal length of the master lens. A 36mm extension tube will have a much more dramatic effect attached to a 50mm lens than the same tube attached to a 400mm lens.

[awahlster]

as an example I use a 15mm extention tube with my 500mm f4.5L to increase the magnification of the lens BUT when I do that the lens will only focus to about 100' but since I do this for backyard bird photography I don't need to focus to infinity. On the other hand with a 2X-A doubler/telextender on the same lens I have been able to get photo's of Saturns moons. pretty sure that is close to infinity as far as 35mm photograhy without a telescope goes!

[brian_keyashian]

Thanks for the info!

 

Brian

[eosdoc]

See if this helps:<br> 

<a target=loser href=

http://ca.geocities.com/lokejul/jlcalc.htm

>http://ca.geocities.com/lokejul/jlcalc.htm</a>