# Extension Tubes?



## dab_20 (Apr 24, 2010)

I was just curious about extension tubes for macro photography. I have seen some awesome pictures with these tubes, but I've been reading some online and it says they are a good alternative to a macro lens, instead of an addition to. 

I have a Sigma 105 mm lens, and I want to get some really neat close up shots like many of the photos I've seen here. But I can't get insects to look that BIG with the lens alone. Is it the tubes that is the key?

How do extension tubes work? I couldn't find many pictures of them. Do they attach to a lens or the camera body? Sorry if this is a stupid question


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## mle (Apr 24, 2010)

_The tube contains no optical elements; its sole purpose is to move the  lens farther from the image plane. The farther away the lens is, the  closer the focus, the greater the magnification, and also the greater  the loss of light (requiring a longer exposure time). Lenses classically  focus closer than infinity by moving all optical elements farther from  the film or sensor; an extension tube simply imposes this movement.

_Extension tube - Wikipedia, the free encyclopedia


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## Dwig (Apr 24, 2010)

dab_20 said:


> ...Do they attach to a lens or the camera body? ...



Yes, ...

... they attach to both.

They mount on the camera body like a lens and the lens mounts onto the front of the extension tube just as it would mount onto a body. Extension tubes are just that. Hollow tubes that extend the lens further from the film/sensor. By moving the lens away from the film/sensor they make it focus closer.

Modern extension tubes also contain electrical extension for the signals that pass between the lens and body. They also provide mechanical extension for any mechanical lens to body interface. Some tubes do not provide a full set of such connections, limiting the level of metering and/or focus automation.

It is true that extension tubes, used with a convention lens, can be a good alternative to a more expensive macro lens. What is also true is that they are even better when used with a macro lens rather than with a conventional lens not optimized for close work.


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## mle (Apr 24, 2010)

Modern ones allow the lens to continue to communicate with the camera body's electronics as normal. In their simplest form however, they are tubes - you can make them from scrap materials if necessary.


*snap* Ah! similtaneous post Dwig!


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## Derrel (Apr 24, 2010)

Below is a web page for a 25mm extension tube in the Olympus 4/3 mount. This page shows an the official, 9-contact, autofocus capable, top-grade Olympus brand extension tube. If I had only one,single tube, it would probably be a 25mm extension for close-up, high-magnification uses with a 100 to 135mm lens where I wanted the biggest subject magnification on small things like bugs.

This extension tube has full contacts, and will maintain all camera functions with the tube installed with AF 4/3 mount lenses on your Olympus camera. Typical lengths are 12, 25, and 36mm, and some of the sets are sold in three-ring sets. Kenko makes the 2nd best full-contact, full function autofocusing extension tubes, which can be bought in sets of 3 from B&H and Adorama and other top retailers. Pro-Optik and Opteka make third-level tubes, which sell for less than the Kenko brand, but still have full contacts and maintain all camera functions. Then there are REALLY CHEAP Chinese-made tubes that have NO electronic contacts whatsoever, and which sell for under $15 on eBay...I cannot recommend those unless you have older Nikon mount or M42 thread mount lenses which have manual diaphragm control; on new cameras and newer lenses, the el-cheapos are a PITA.

Olympus ZUIKO DIGITAL Extension Tube EX-25 Overview at DentonImages.com


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## dab_20 (Apr 26, 2010)

Wow thanks for the comments everyone. Very helpful. 

Derrel, thanks so much for the link. I will try and surf the web for the best prices on that extension tube.


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## candacebanks (May 1, 2010)

i recently bought one off ebay for 75 bucks and so far haven't really noticed a difference...maybe i need to play with it more.  i'm desperately wanting a macro lens but 75 was a much better price...good luck!


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