Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-15-2011, 11:27 AM   #1
Pentaxian
philbaum's Avatar

Join Date: Oct 2007
Location: Port Townsend, Washington State, USA
Posts: 3,659
Does this make sense for an SDM expansion tube?

I have this 50-135 which I like a lot. But it would be useful to have an expansion tube to allow me a better closeup for leaves, flowers and things.

Adorama has a ProOptic 2x teleconverter for under $100 with pz contacts. Could i buy that and remove the lens to get me an expansion tube with pz contacts for my sdm lens to work?? I don't mind manual focusing, but there's no aperture ring on this lens. If i don't get an sdm expansion tube, am i out of luck in setting aperture for photos?

I've seen cheaper 2x teleconverters with the electrical contacts and screw drive. If i buy one of those, will it cause my 50-135 to work on screw drive with my K5?? If so, i could get by with a cheaper solution.

I have the pentax 35mm macro lens, but I don't think its going to get me the kind of background i'm looking for in my close-in shots.

Any help much appreciated - thank you!

12-15-2011, 11:35 AM   #2
Veteran Member
dgaies's Avatar

Join Date: Oct 2009
Location: Maryland / Washington DC
Posts: 3,917
That should work, but frankly you can do it a lot cheaper. I've bought several older 2X TCs with Pz-AF contacts to use as extension tubes and they generally only cost about $30-40. Here's a thread with an example of their use with a DA*55. With the DA*55 I was actually able to het very good AF using LV. I don't recall off hand if AF worked with the 50-135, but certainly you can control the aperture and manually focus if it doesn't.

FWIW, the TCs with just screw drive will not allow you to use the screw drive of the 50-135.

Last edited by dgaies; 12-15-2011 at 11:54 AM.
12-15-2011, 11:51 AM   #3
Veteran Member




Join Date: May 2009
Location: Twin Cities, MN
Posts: 2,869
I found the AF more reliable with the PZ contact TCs using liveview as well, including with the 50-135mm. Makes sense since it is a different type of focus (contrast detect vs phase detect). Contrast detect doesn't rely on the amount of light, but rather being able to see contrast in the subject, so the dimmer light hitting the sensor doesn't affect the AF like it does with phase detect.
12-15-2011, 01:43 PM   #4
Veteran Member




Join Date: Jan 2009
Location: Victoria, BC
Photos: Gallery | Albums
Posts: 310
Perhaps the question should be: Does SDM Extension Tube makes sense ? Not likely that AF will be of much use on extreme close-up.

12-15-2011, 02:01 PM   #5
Veteran Member
dgaies's Avatar

Join Date: Oct 2009
Location: Maryland / Washington DC
Posts: 3,917
QuoteOriginally posted by regor Quote
Perhaps the question should be: Does SDM Extension Tube makes sense ? Not likely that AF will be of much use on extreme close-up.
Whether or not it makes sense in terms of being able to AF isn't really the question. You need all the contacts on the tube, aperture and Pz-AF, in order to be able to control a DA* lens properly with the extension tube in place. A simple mechincal extension tube will not work well with a DA* lens without an aperture ring

As far as AF on extreme closeups. It may not be neccesary, but the fact of the matter is it does work quite well in LV on a K-5. If you take a look at the link I posted in my first reply, those shots were taken using AF. I certainly could have used MF in LV instead, but I assure you it was easier and more accurate to use AF in that situation.
12-15-2011, 02:14 PM   #6
Pentaxian




Join Date: Jan 2010
Location: Vancouver, BC
Posts: 1,421
QuoteOriginally posted by pxpaulx Quote
I found the AF more reliable with the PZ contact TCs using liveview as well, including with the 50-135mm. Makes sense since it is a different type of focus (contrast detect vs phase detect). Contrast detect doesn't rely on the amount of light, but rather being able to see contrast in the subject, so the dimmer light hitting the sensor doesn't affect the AF like it does with phase detect.
OP isn't after a Pz-AF TC to use as a focal length doubler, he wants to remove the glass from the TC to turn it into an extension tube and retain the SDM focus function when coupled with his 50-135. I have a Tamron Pz-AF 2x TC that I no longer need but there is no way for me to test the SDM function because my one and only SDM 17-70 is now an MF lens and the TC doesn't work well with MF, A series lenses (reports aperture value starting from f1.2 regardless of the lens attached). PM if interested, but it will be priced a bit higher than what dgaies paid for his, as I had paid more for mine when I acquired it.
12-15-2011, 02:41 PM   #7
Veteran Member




Join Date: May 2009
Location: Twin Cities, MN
Posts: 2,869
Was just disussing the AF aspect of the OP's original post and Dgaies' reply, not the teleconverter aspect, which I know will be removed, thanks tho
12-15-2011, 02:53 PM   #8
Pentaxian
RonHendriks1966's Avatar

Join Date: Jan 2009
Photos: Gallery
Posts: 8,556
My experience was that it doens't work sufficent enought (with DA*50-135mm) to purchase this thing. But without glass you would have it working I guess and have a good close-focus lens.

12-15-2011, 02:55 PM   #9
Veteran Member
dgaies's Avatar

Join Date: Oct 2009
Location: Maryland / Washington DC
Posts: 3,917
QuoteOriginally posted by RonHendriks1966 Quote
My experience was that it doens't work sufficent enought (with DA*50-135mm) to purchase this thing.
Keep in mind we're not talking about using the TC as a TC, but rather to remove the glass and use it an an inexpensive extension tube with aperture contacts such that the body can control the aperture on lenses that don't have a ring (like the DA* lenses).
12-15-2011, 03:32 PM   #10
Pentaxian
cmohr's Avatar

Join Date: Apr 2011
Location: Brisbane. Australia
Photos: Gallery | Albums
Posts: 1,085
I use the Kenko 1.5x Pz on my 50-135 and the SDM works perfectly, I suppose if you removed the elements it would create a SDM extesion tube, but as others pointed to, macro tends to be a selective focus thing and not overly suited to AF, not completely anyway. I'd say give it a go, if it doesnt work, just put the elements back in and use the 1.5x TC SDM..
12-15-2011, 05:57 PM - 1 Like   #11
Veteran Member
dgaies's Avatar

Join Date: Oct 2009
Location: Maryland / Washington DC
Posts: 3,917
QuoteOriginally posted by cmohr Quote
I use the Kenko 1.5x Pz on my 50-135 and the SDM works perfectly, I suppose if you removed the elements it would create a SDM extesion tube, but as others pointed to, macro tends to be a selective focus thing and not overly suited to AF, not completely anyway. I'd say give it a go, if it doesnt work, just put the elements back in and use the 1.5x TC SDM..
I'd be hesitant to remove the glass from a Kenko 1.5x. They're pretty decent optically and worth too much IMO as a TC to risk taking it apart for use as a tube (unless you're really confident you can reassemble it correctly). Finding a used 2x TC (which is optically mediocre, and worth a lot less as a TC) with aperture/PZ-AF contacts is a better solution since they tend to run between $30-50 (for the less expensive 4 element versions).

Here's a picture of what they look like, taken from my ad from a few months back; they were sold under a dozen different names, but they're pretty much all the same.

12-15-2011, 09:20 PM   #12
Pentaxian
philbaum's Avatar

Join Date: Oct 2007
Location: Port Townsend, Washington State, USA
Posts: 3,659
Original Poster
Thanks to all for the assistance on the extension tube, particularly DGaies identifying some of the brands that are appropriate.

I do have a Tamron 1.4xTC with Pz points, but it works fine with the 50-135 as a teleconverter - occasionally misses a lock inside the house but otherwise ok. Its one of the optically good ones, so i'll leave it alone and try to find one of the less optically fine ones.
12-15-2011, 09:24 PM   #13
Veteran Member
dgaies's Avatar

Join Date: Oct 2009
Location: Maryland / Washington DC
Posts: 3,917
QuoteOriginally posted by philbaum Quote
Thanks to all for the assistance on the extension tube, particularly DGaies identifying some of the brands that are appropriate.
You're welcome. Ideally when you're looking for one, try to look at the mount (front or rear) and you should be able to confirm if there are both aperture and Pz-AF contacts. As you can see from the picture above, it would be hard to tell from that shot which three had Pz-AF contacts and which one didn't (If I recall correctly, the one in the upper right did not have Pz-AF contacts). But anything marked "AF" should have the aperture contacts.
12-15-2011, 09:35 PM   #14
Loyal Site Supporter
drougge's Avatar

Join Date: Jan 2010
Location: Malmö
Photos: Gallery
Posts: 787
I have a 25mm extension tube with all the electronics passed through. (Passive pass through, maybe the TC has a chip in it?)

Using this and my DA* 50-135 I can tell you that:

The lens is a modern IF zoom design, 25mm extension gives you much more closeup than you would expect. Zoom affects focus massively, and don't expect to shoot anything reasonably large. (It's also not a particularly good macro, at least not as I tested it.)

AF works, but only affects focus a little. (You have to zoom until it's very close.)

Without SDM contacts (I tried putting tape over them), AF doesn't work, but aperture still does.
Same if I disable the data pin as well (using foil, since it needs to be shorted).

So, you can use any extension tube that has electrical contacts, even if it only has A contacts. But you probably don't actually want to.
12-15-2011, 10:09 PM   #15
Pentaxian
philbaum's Avatar

Join Date: Oct 2007
Location: Port Townsend, Washington State, USA
Posts: 3,659
Original Poster
QuoteOriginally posted by drougge Quote
I have a 25mm extension tube with all the electronics passed through. (Passive pass through, maybe the TC has a chip in it?)

Using this and my DA* 50-135 I can tell you that:

The lens is a modern IF zoom design, 25mm extension gives you much more closeup than you would expect. Zoom affects focus massively, and don't expect to shoot anything reasonably large. (It's also not a particularly good macro, at least not as I tested it.)

AF works, but only affects focus a little. (You have to zoom until it's very close.)

Without SDM contacts (I tried putting tape over them), AF doesn't work, but aperture still does.
Same if I disable the data pin as well (using foil, since it needs to be shorted).

So, you can use any extension tube that has electrical contacts, even if it only has A contacts. But you probably don't actually want to.
Well thats consistent with the macro pictures that dgaies provided in his link in post #2. taken with a 2x TC. They were remarkably large enlargements. Nice to hear that one doesn't need pz contacts for aperture control.

Thank you!
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
2x, aperture, contacts, drive, expansion, k-mount, lens, pentax lens, screw, sdm, slr lens, tube
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Does Employment at Will make sense? GeneV General Talk 34 11-07-2011 11:33 AM
If I have the 16-50, does it make sense to get the 15mm ƒ4? Sperdynamite Pentax SLR Lens Discussion 21 10-24-2011 11:05 PM
People yeah.... a pony tail would make sense dcmsox2004 Post Your Photos! 2 07-16-2011 07:18 PM
Do RML's posts make sense to you? Ash General Talk 46 11-09-2009 11:22 AM
Ken Rockwell's latest... does it make sense? rpriedhorsky Pentax SLR Lens Discussion 38 05-31-2009 10:49 PM



All times are GMT -7. The time now is 08:15 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top