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05-25-2007, 04:38 PM   #1
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extender tubes

extender tubes? what exactly are these? are they worth spending money ion instead of a macro? and for just a peice of plastic tube do the work?

cheers james

05-25-2007, 07:23 PM   #2
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Hi James,

Extender tubes, also called extension tubes are the poor mans alternative to buying macro lenses. I have a nice set from Kenko that I use with my manual SLRs, I haven't looked for a digital set yet. The tubes are installed between the body of the camera and the lens and reduces the focal length of the lens. Tubes can be purchased individually or in sets (generally of 3) that can be used alone or combined to allow you to use your lenses at different focal lengths. One of the things I like about the extension tubs is that I can use all of my existing manual lenses with it, but I'm partial to my 100mm F/2.8.

I also have a set of Pentax Bellows that lets give more flexibility than the extension tubes but it is bulkier. The one thing that I highly recommend is to always use a tripod when using either extension tubes or a bellows.

As for are they worth it, in my opinion they are. They use the locking ring on the camera and are very strong. You may also want to look into a ring flash since the lens is farther away from the body a popup flash will not work well and a hot shoe flash may hit the front of the lens.

hope this helps.
Shawn
05-25-2007, 09:46 PM   #3
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totally agree there - if you're on a budget but want macro capability - get the extension tubes. You can use any lenses, though fast primes are better simply because they allow more light in (you lose some light with the extension, so you need all you can get)

my (kenko) set has a 12mm, 24mm and 36mm tube that can be combined however you wish.
also, with the extension tubes you lose some of the focusing range, so you'll have to physically move the camera closer or farther away, depending on how much extension you put on, etc...

lots of pros and cons to each - but if you don't have a budget for a dedicated macro lens, extension tubes are the way to go - often can be picked up cheap used - try keh.com - i got mine there for maybe $40 - that was a while back though, before Pentax's resurgence.
05-26-2007, 04:08 AM   #4
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I have a set of Pentax extension tubes, made specifically for the old S3 film body sometime around 1960. I think I paid somewhere around twenty bucks for them. They do a wonderful job combined with my M42 lenses. Dabbling in macro needn't cost one a small fortune.

05-26-2007, 04:26 PM   #5
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brill, i was have a flick through ebay and saw a set for sale for 12 ($25-30) and thought surely they cant do anything, not for that price but it might be worth a shot as with buying the camera the funds arnt allowing a new lens just yet.

cheers for all the advice guys much appreciated.
05-26-2007, 07:03 PM   #6
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Well, that's the whole thing, James. They don't have to do anything....other than hold the lens and the camera body apart from each other.
05-26-2007, 08:03 PM   #7
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Funny you'd bring this up. I was just yesterday trying to find a set for my K100D. You can buy new Auto-Focus sets for around $130-$140. The rub is that they won't auto-focus on DSLRs. The alternative is the Chinese knock-offs on E-Bay. Just machined aluminum tubes with screw on K mounts but from what I've read they work fine. They'll cost you $15-$20 for a set of three. Apparently though you have to use them with lenses that have an aperture ring or you can't adjust the f-stop.

Oh, one other thing, because you're moving the lens forward you can expect 2-3 f-stops less light actually reaching the CCD.
05-27-2007, 07:36 AM   #8
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ETs are great.
if you get a set at least get the ones that have the aperture lever in them so you can meter wide open and hit the AE-L or green button to meter. otherwise you have to use the lens stopped down. macros need a small aperture for the DOF needed and the VF is awfully dark at f16

05-27-2007, 01:33 PM   #9
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QuoteOriginally posted by roy Quote
ETs are great.
if you get a set at least get the ones that have the aperture lever in them so you can meter wide open and hit the AE-L or green button to meter. otherwise you have to use the lens stopped down. macros need a small aperture for the DOF needed and the VF is awfully dark at f16
Roy is right. I bought a second hand set of nice Panagor tubes with an aperture lever after giving up trying to use genuine Pentax ones without a lever as the viewfinder was too dark to get a good focus unless the aperture was wide open. They were quite cheap as well, 25.
05-27-2007, 04:35 PM   #10
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mine were 15usd delivered. there is no name on them.. why is everything twice as expensive in the UK.?? the EU is also high. i know the usd is slipping worldwide but our costs are so much better. is there a reason for this??
05-28-2007, 05:36 AM   #11
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there are a couple of misleading posts here with respect to extension tubes and what they do.

Extension tubes do not reduce the focal length of a lens.

extension tubes do move the lens forward and away from the focal plane which has the effect of changing the range of focus of the lens.

this allows you to focus closer than the minimum focus distance of the lens, at the loss of infinity focus. By allowing closer focus and shorter lens to subject distance, the image is inherantly larger, hence the use in macto photography.

extension tubes also allow for another use, specifically on long telephoto lenses, where the close focus distance, say of a 400 mm lens might be 20 feet or more. an extension tube would allow you to get closer to the subject. This might not seem important when you consider the magnification of a 400 mm lens, but a 2 inch high bird is still awfully small at 20 feet. if you can get closer, you get a better image. Imagine for example, having a blind set up close to either a nest or feeder. you can get really close, but the lens might not permit it.
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