Extension tubes?!?!?!?!?!

[RbrtPtikLeoSeny]

I was just looking at some Extension Tubes at bhphoto.com, and I'm curious.... what are they for? It says it helps the lens focus at closer distances, but to what consiquence? Loss of image quality?

And what sort of situations would an extension tube be needed?

[rssfhs]

Extension tubes are for macro photos. You can only use them with lenses longer than about 100mm. They do make things darker, but if you use ISO 400 instead of 100 or 200 it works fine.
I have taken lots of good flower and insect shots using a Canon 25mm extension tube with my Canon 28-135 mm f/3.5-5.6 IS USM. Here is one of them: http://www.usefilm.com/image/695923.html

[sid]

You can only use them with lenses longer than about 100mm.
I dont think thats true. You can use extension tubes with any compatible lens. For example, many people use the Canon 25mm (Or Kenko) extension tube with the 50mm f/1.8 lens...

[CyberDyneSystems]

They work "better" with lenses longer than 50mm.. my favorite "macro" lens for years was a 70-200mm with tubes.

[cfcRebel]

I'm curious about ET too. I found this http://photography-on-the.net/forum/showthread.php?t=69217

[cmM]

they don't work properly with lenses that are too wide, but they work just fine with a 50mm lens for example
There's no glass, so image quality shouldn't change much

[CyberDyneSystems]

.. Oh yeah/... just to clarify.. when I say "better" should have said "imho" .. I just like a little more distance to work with.

[ron chappel]

Extension is one of several ways to acheive closer focusing.
Oddly, lenses focus to infinity by moving close to the camera while moving the lens away lets it focus at closer distances

Another technigue is to reverse a lens onto the camera (works best with wider lenses-try it with the kit lens,it's amazingly powerfull :))

The last option is to attach diopters to the lens -basically identical in principle to a magnifying glass.Reversing one lens onto another is a variation of this .

You can easily experiment with all of these methods without buying anything (out of interest to see how they work)
To try extension simply hold the lens some distance from the camera(anything from a few mm to a foot if you can hold it straight!:)).Try different zoom settings while doing it.

The reverse thing is easy.Be abit carefull not to scratch the lens on the camera parts though

For trying diopters simply hold a magnifying glass or reversed lens in front of the normal lens

[willg]

i use my canon 12mm extension tube a lot...i got it on ebay for ~$50 i think here is a sample:

http://uploads.jzl.us/files/berry.jpg

[willg]

o yeah...i have a lot of trouble with dof so basically you have to stop down a whole lot and use a tripod

[robertwgross]

The trouble with using extension tubes is that the infinity focus is lost immediately.

So, if you are going after a bumblebee on a flower, they work good. If you suddenly swing upward to frame on the deer across the meadow, they don't work so hot.

---Bob Gross---

[RbrtPtikLeoSeny]

Huh, so then it would be worth it to buy one for my 70-200mm f/4L lens that I'm getting soon? cause I LOVE macro, and don't feel like spending 400+ bucks on a new lens. So, I figured one of these tubes would surfice. Good idea? Yes, no?

[pierrot]

Yes of course. And using an ET with a tele zoom is very easy: using a long focal you're not obliged to be too close from the subject, and if using a tripod you can achieve focusing in zooming instead of moving the camera or the subject. ;)

[foxbat]

Extension tubes are popular with long telephoto users as they reduce the minimum focus distance, and they can be stacked. They also provide a small increase in magnification when used outside the minimum focus distance of the lens at a cost of somewhere between 1/6 and 2/3 of a stop of a light.