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12-27-2011, 03:59 PM   #1
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What extension tube to get??

I have been reading up on extension tubes all day and i am still confused as to what to get and what will work. I have a few DA lenses (18-135/ 16-45) as well as the FA 50mm f1.4 lens. From what i can make sense of the 50mm lens is the one i can get the best use of an extension tube with. Is that correct? What do i need to look for in a tube, or what tube should i be looking at to work with the lenes i have?

Thanks in advance!

-Chad

12-27-2011, 04:21 PM   #2
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Yep, the 50mm is your best bet, as it has the aperture ring you need. For tubes, I have a set of Vivitar AT-22 tubes, and they work very well. They have mechanical aperture linkage. There are also cheaper plain ones (AT-21) that don't have any linkage, and those are more common, but a bit more hassle to use. Finally (for that brand) there's the AT-23 which have all the electronic contacts for AF use and such. They're rare and expensive, and probably not much more useful than the AT-22. Autofocus is not your friend for macro. The depth of field at these magnifications is so thin that it's much easier to move the camera to obtain focus, than to try to hold it still enough to use AF. If you're using a tripod, focusing rails will help a lot, as they allow much more precise movement.

Anyway, back to tubes, there are basically those three types available in whatever brands. Entirely manual, cheap, like $10 on Ebay; Auto tubes, less common, allow for stop down metering; and AF tubes, which should preserve all functions and information between lens and camera, whether it's needed or not.
12-27-2011, 04:31 PM   #3
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Hi Chad.

The answer again is going to be general unless you specify your needs. You can pick up a set of manual tubes quite cheaply, to get you started - I have the Pentax set of three (approximately 9, 19 and 29 mm), but there are cheaper ones around that are probably just as good. There are others available that give you auto aperture and focus, if you want to pay a lot more.

There are also various close-up (supplementary) lenses, and reversing rings, that you might consider. The point about reversing rings is that, for very close subjects, you have the optics working better, ie the lens to sensor distance is greater than the lens to subject distance, which is closer to the designer's intent in that situation than maintaining the usual configuration without the reversing ring.

I hope that helps.

Rob
12-27-2011, 04:31 PM   #4
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So if i just get one of the cheap manual tubes on ebay, it will work ok with my FA 50mm lens? Thats why i was thinking it was the best suited lens, because of it having the aperture ring.

12-27-2011, 04:38 PM   #5
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QuoteOriginally posted by RobA_Oz Quote
Hi Chad.

The answer again is going to be general unless you specify your needs. You can pick up a set of manual tubes quite cheaply, to get you started - I have the Pentax set of three (approximately 9, 19 and 29 mm), but there are cheaper ones around that are probably just as good. There are others available that give you auto aperture and focus, if you want to pay a lot more.
This is where i'm getting confused. Everywhere i read about the tubes it says that if you use a lens that doesnt have an aperture ring then you have no way to adjust the aperture while using that lens with the tube.
12-27-2011, 04:45 PM   #6
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QuoteOriginally posted by Irish Pride Quote
This is where i'm getting confused. Everywhere i read about the tubes it says that if you use a lens that doesnt have an aperture ring then you have no way to adjust the aperture while using that lens with the tube.
If you have a lens without an aperture ring (DA lenses for example), the you would need extension tubes with electrical contacts if you want to be able to control the aperture. You'd also get the benefits of being able to use the flash (P-TLL) more easily when you have tubes with contacts.

FWIW, AT-23 tubes don't have an AF coupling, which isn't a huge deal, as you almost certainly wouldn't want/need to use AF with tubes.
12-27-2011, 04:48 PM   #7
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A tube with electrical contacts will allow the camera to control the aperture of the lens (assuming the lens does not have an aperture ring, or has an aperture ring set at A). If the tube has no electrical contacts, but has mechanical linkage, it can be used with a lens with aperture ring.

These tubes have electrical contacts and thus can be used with DA lenses (the one on the right is a 2X teleconverter with the glass removed):

12-27-2011, 04:52 PM   #8
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There was just an (likely) example of flare with cheap tubes on the forum. The cheapest well made tubes that still allow auto exposure are the best value--but realize that means you cannot effectively use DA lenses (no aperature ring). Pentax should be a safe bet. Better 3rd party (e.g., Vivitar) should be fine. But I have no personnel experience with Pentax or 3rd party tubes (only ones I used were Alpa--so quality was a given).

12-27-2011, 05:06 PM   #9
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Since the depth of field will be very shallow, you need to control the aperture either manually or via the camera body. The DA zooms without aperture rings are not suitable for the cheap mechanical tubes. If you get the Vivitar AT-23, it has all the contact to communicate focal length and aperture. It does not have the screw drive mechanism for autofocus though so you'll be doing manual focus which is the preferred way.

Depending what you are trying to photograph and the magnification you want, you may consider getting a bellows unit. That will give you a more flexible solution and much higher magnifications. If you go that route though, lighting becomes problematic and you should consider off camera flash options to provide for good exposures. Again depending on the subject and its size, you'll be using F-stops in the range of F11-F22 to get enough DOF. The small F-stop and the extension will require exposures measured in several seconds so a flash helps.
12-27-2011, 06:47 PM   #10
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I cover this a bit in this article: https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html. Scroll down to the A-TYPE EXTENSION section and the CHEAP EXTENSION section. Basically, to use DA lenses on extension, you MUST have an A-type tube. Such tube sets are not common and not cheap. The cost-effective trick is to get old A-type teleconverters and remove the glass. See the article for more details. Good luck!
12-27-2011, 09:31 PM   #11
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QuoteOriginally posted by RioRico Quote
I cover this a bit in this article: https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html. Scroll down to the A-TYPE EXTENSION section and the CHEAP EXTENSION section. Basically, to use DA lenses on extension, you MUST have an A-type tube. Such tube sets are not common and not cheap. The cost-effective trick is to get old A-type teleconverters and remove the glass. See the article for more details. Good luck!
Thanks, i think i've got a better understanding now. I'm like Cole Trickle from Days of Thunder. I have a good eye and can take good pics but i dont really understand the process of how everything works yet or the jargon that goes with it.
12-27-2011, 11:00 PM   #12
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QuoteOriginally posted by Irish Pride Quote
i dont really understand the process of how everything works yet or the jargon that goes with it.
The two are one. Jargon is the language that describes the technologies and techniques of photography. Think of PFC as an ongoing language seminar, not quite total immersion but totally hands-on and eyes-on.

Read books! I can't recommend specific books on digital gear -- maybe a FOR DUMMIES book? Anyway, browse your local public library for everything on photography, current and historical. It's all significant.

And of course RTFM. Eight years on, I still re-read the manual for my favorite advanced P&S. Alas, the manual doesn't cover everything, which is where these forums come in. On to the next language lesson!
12-27-2011, 11:17 PM   #13
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Oh trust me, in the week or so since i've been on the forum i've learned so much. I've just been reading and reading and reading. I've had my camera for about 9 months now and i just thought i could teach myself. LOL I cant believe how far i've come in just a week of actually trying to learn.
12-28-2011, 02:24 AM   #14
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Of course are also different levels of stuff to know -- general photography, and digital, and Pentax specifics, and camera specifics. I could rant about this a bit, but that's getting a bit off-topic. Going back to extension:

* AF macro tubes aren't really helpful for most close work. At macro ranges, manual focus is a must. An exception would be when using a long lens. Example: I use to put a long MF tele on tubes and bellows and a shoulder stock, to shoot daylight closeup photos of live rattlesnakes in the wild from a safe distance, say 3-4m. Putting 100mm of AF extension behind my Lil'Bigma 17-500 would be handy for that sort of thing.

* A-type tubes or deglassed A-type TCs are vital with DA-type lenses, and are nice-to-have with FA, F, and A lenses. The nice-to-have-ness isn't so much for direct aperture control, as for being able to use pTTL flash. I pretty much only use mine for flash work.

* M-type tubes or deglassed M-type TCs are probably useful in some circumstances, especially when using older TTL-flash-supporting cameras. I've not done this so I can't comment coherently.

* Simple cheap PK tubes are useful for many other things. I use them as mounts for large and weird non-camera (enlarger-projector-copy-process-etc) lenses, and as test-beds for figuring out lens base mods, and as hoods on reversed lenses. As with M42 tubes, I'll use them as fixed-focus mounts, or to extend a bellows' range, or just to pull in a long lens' focus a bit.

* Bellows offer more flexibility (and bulk) than tubes, at the cost of losing all lens automation EXCEPT with certain specific lenses with a separate aperture link. Don't worry about that. Mostly, bellows are great in ambient or controlled light conditions (no flash) and for exploiting all sorts of non-camera lenses. I could rant about this a bit too. I'd better stop now.
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