The use of extension tubes...

[mermoz]

Does it noticeably reduce the original IQ of the lens - sharpness, colors, contrast...?

[canuck_newbie]

Not at all.
There's no optics in them, so nothing to degrade the light

[olz]

No... Extension tubes are simply hollow tubes without glass that allows your lenses to focus closer. Tele converters on the contrary degrade IQ to some degree.

[mermoz]

Thanks, guys

[KevC]

It doesn't *directly* affect IQ since there are no optics as previously stated. However, they do force lenses to focus *outside* regular operating conditions, where sharpness/contrast/etc is not optimised (focussing so closely).

However, stopped down (as you would always anyway in macro) and with a sharp prime like the 50mm, it should produce beautiful results.

[Headcase650]

The only disadvantages of using tubes over a true macro is that you loose any distant or infinity focus, your focusing distance is very close but also narrow, many times its easier to use the zoom ring to achive proper focus or move the lense closer or further from the subject. You also loos a lot of light, 1 stop or more depending on how many rings you are using, this mean you have to increase ISO to get fast shutter speeds and this increases noise, but this can be fixed with a good noise reducer, noiseware community eddition is free and works very well.

[chris.bailey]

As mentioned above, extension tubes do stretch a lens capability and you might notice some chromatic aberration around the edges. Using mine, the best lens for it is the 28-70 and the 50mm 1.4 comes out quite badly surprisingly with quite noticeable CA

[Dchemist]

I have set of Kenko tubes and used them with a 135F/2 and thought the images were excellent. The Kenko tubes have a plastic feel to them but they are otherwise fine. Dennis

[olderokie]

Where can the extension tubes be purchased

[Headcase650]

I have the pro optics
http://www.adorama.com/MCAETEOS.html?searchinfo=pro%20optic%20eos%20canon&item_no=1
They work just fine and fit EF and EF-S lenses and retain full electronic connection between camera and lens.

[FlashZebra]

Not at all.
There's no optics in them, so nothing to degrade the light
Pushing a lens out to distances away from the image plane, that were not specifically designed for those working distances, most certainly degrades the image quality from that lens, despite the lack of optical elements. The introduction of lens elements is only one, of many, aspects of optical design.

This does not mean the produced image would necessarily be unacceptable.

Enjoy! Lon