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07-07-2012, 09:34 AM   #1
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Extension Tubes

One item on my wish list for Pentax lens accessories is a set of Pentax extension tubes. I wonder how many Pentax photographers would be interested in purchasing such a product if Pentax actually began manufacturing a set of extension tubes. I am using a set of Kenko tubes on my 300mm DA* telephoto, but my 25mm tube is out of commission and the remaining tubes do not provide focus confirmation. Nor do they send correct aperture info to the camera body. My design qualification for a set of tubes is that all electrical contacts (even af) must be present so that the correct exposure settings and aperture info are relayed from body to the lens. I wish Pentax provided a suggestion box on their web sites so that marketing execs could know what equipment photographers need. Let me know what you think................Jim

07-07-2012, 09:54 AM   #2
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Jim, I would add that to my wish list as well. But I doubt it will ever happen, the potential market is just too small. We have been waiting for years (and still do not have) a tele-converter from Pentax which would have a much larger market and potential profit. This is now on the lens road map but I'll believe it when I see it.

The vast majority of camera buyers would have no idea what an extension tube is. This is a niche market and I think the best hope would be to have one of the ebay companies that make lens adapter and so on make one. They seem to do OK making things with small markets.
07-07-2012, 10:44 AM   #3
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Hi,

Yes, the niche market has not treated nature photographers well. I was shocked to see the 300mm f4 DA* come to reality--atypical for a Pentax lens. Considering the number of insect and flower shots I see on these blogs, extension tubes may have a bigger market than what has been realized so far. Pentax used to make some fantastic macro equipment and the LX was also a fantastic pro film slr body in the '80s. I may have to remove the glass from my Vivitar 2x macro teleconverter. It may function as a helicoid extension tube.........Jim
07-07-2012, 04:34 PM   #4
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QuoteOriginally posted by Jim Z. Quote
I am using a set of Kenko tubes on my 300mm DA* telephoto, but my 25mm tube is out of commission and the remaining tubes do not provide focus confirmation.
That's a function of (effective) aperture. It doesn't matter what you use for tubes, the same thing will happen, so long as the effective maximum aperture is too slow for the AF sensor, and/or there isn't enough light in the scene. The 9 cross type AF points are good up to f./8, and the vertical one on each side is good til f./5.6. This refers to the aperture you're using to focus, not what you stop it down to, to shoot. There also has to be sufficient light, or even a very large aperture isn't going to help.

QuoteOriginally posted by Jim Z. Quote
Nor do they send correct aperture info to the camera body. My design qualification for a set of tubes is that all electrical contacts (even af) must be present so that the correct exposure settings and aperture info are relayed from body to the lens.
If it's a Kenko set with the six electrical contacts, it should indeed communicate the correct aperture between body and lens. Perhaps try cleaning all the contacts, each segment of tubes as well as camera body contacts and the ones on the lens. Sometimes they look just fine but have a thin film on them that interferes. A clean, dry cloth is your best bet to buff them up a bit.

AFAIK, the six contacts communicate everything the lens is capable of communicating normally. They're just dumb pass-through extensions. AF capable tubes would have to have the screw drive pass through as well. I think a couple sets exist, but I can't remember names. AF is pretty much useless for macro anyway, imo, so I don't worry about it.

07-07-2012, 07:21 PM   #5
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QuoteOriginally posted by Philoslothical Quote
AF capable tubes would have to have the screw drive pass through as well. I think a couple sets exist, but I can't remember names. AF is pretty much useless for macro anyway, imo, so I don't worry about it.
I have a set of Kenko tubes I bought from Hunt's Photo & Video in Melrose, MA in 1994 for $100. They are the "AF" tubes but they don't have a screw-drive passthrough, they just pass through the electrical contacts. To my knowledge no AF tubes ever extended the screw-drive to Pentax lenses, they all presume you will use manual focus for macro work (rightfully so, though it does make the "AF" printed on the side of them somewhat confusing).
07-08-2012, 03:21 AM   #6
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QuoteOriginally posted by nater Quote
I have a set of Kenko tubes I bought from Hunt's Photo & Video in Melrose, MA in 1994 for $100. They are the "AF" tubes but they don't have a screw-drive passthrough, they just pass through the electrical contacts. To my knowledge no AF tubes ever extended the screw-drive to Pentax lenses, they all presume you will use manual focus for macro work (rightfully so, though it does make the "AF" printed on the side of them somewhat confusing).
Unless they also pass the SDM contacts (and I've never heard of tubes that do), that's downright deceptive. The AF confirmation beep/light doesn't require any contacts, it'll work with m42 lenses, or anything else, as long as there's enough light and the aperture is large enough.
07-08-2012, 06:26 AM   #7
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I'd like to see "A" type extension tubes at least.
For example, a common criticism of the DA 70 is that it only focuses to 70cm.
An "A" type tube would let us get closer with that lens.
MF is OK, but the default aperture isn't.

For macro, apart from the DA 35 Ltd, I've only bought lenses with an aperture ring
(working with a set of heritage Pentax "auto-aperture" extension tubes),
and would not consider the current D FA 100mm F2.8 Macro WR.
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