Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-12-2012, 10:33 AM   #1
Inactive Account




Join Date: Aug 2007
Location: Illinois
Posts: 7
Sigma 150-500 HSM and Sigma 2X TC

Just a question, but why does the Sigma 150-500 HSM not work with the Sigma 2X TC? is it the HSM or is it an issue with the mount? Just curious to see if I want to keep the zoom seeing as I also have the Sigma 300mm 2.8 and the TC.....is it worth the overlap. And do I really need a MF 1000mm F13 lens????

01-12-2012, 02:09 PM   #2
Pentaxian
cmohr's Avatar

Join Date: Apr 2011
Location: Brisbane. Australia
Photos: Gallery | Albums
Posts: 1,085
The Sigma TC's don't have the SDM contacts in them to power the HSM in the Sigma lens. Only screwdrive.

You could try a Kenko or similar 1.5x PZ version, I know mine works with my DA SDM zooms and my 8-16 HSM, so would imagine it would work on the Bigma.
01-12-2012, 02:34 PM   #3
Senior Member




Join Date: Sep 2010
Location: Innsbruck
Posts: 283
But it could become to dark for the AF
01-13-2012, 12:52 PM   #4
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
there are three issues with respect to sigma TCs.

one issue is mechanical, one electrical, the other is optical.

the mechanical issue is that sigma TCs have a somewhat proud or forward extending front element, that requires a circular recess in the rear of the lens roughly 35mm in diameter, and a minimum of 12mm deep.

Many lenses do not have this type of recessed rear element or rear barrel inner diameter, and the TC simply does not fit.

Other lenses , like the BIGMA (i;e sigma 50-500) have a focal length restriction, as at 50mm the rear element hits the TC and therefore there is a restricted focal length on the bigma.

the electrical issue is in 2 parts, first, sigma TCs for pentax are not HSM compatible, so if your lens is HSM forget it, you have MF only. Second, the TC feeds lens data unmodified, and therefore your aperture is not correctly reported, which is OK but can lead to the need for exposure compensation, and it also messes up P-TTL flash

the optical issue is that on any camera for the AF to work reliably you need a maximum aperture of F6.7 or larger, and therefore the AF does not work with either the 1.4x or your 2x TC (Or any other TC for that matter)

I am not sure whether the TC can be mounted to your lens, but if it can you are limited to a dark viewfinder to focus with manually

01-13-2012, 01:34 PM   #5
Pentaxian




Join Date: Feb 2009
Location: Alameda, CA
Posts: 3,194
In terms of autofocus, the issues of TC for SDM lenses are much more than just electrical contacts and aperture. I don't think anyone has figured it out yet. Here are the symptoms I observe:

1. There is NO 2X TC that works with SDM lenses. Example: the Tamron 2X TC has electrical contacts, yet is does not work at all with any SDM/HSM lenses. For DA* 50-135 F/2.8, the effective aperture with the TC is F/5.6, still it doesn't work.

2. Even for 1.4X TC, autofocus is iffy at the long end (there is no reason to use a TC at the short end). On half-press of the shutter release, the autofocus keeps going back and forth as if it can't decide. If you release the half press and half press again, it MAY lock in focus. This is not due to aperture not large enough because the lenses works fine with Pentax 1.7X AFA. I've heard that the Tamron 1.4X TC works with DA 16-45 F/4, but I don't have the lens so can't confirm that myself.
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, hsm, pentax help, sigma, sigma 150-500 hsm, tc
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Sigma 150-500 HSM AGWoodard Sold Items 8 10-16-2011 02:51 PM
IQ for 150-500, 50-500, 120-400 Sigma's? saladin Pentax SLR Lens Discussion 10 07-30-2011 04:57 PM
Wanted - Acquired: Sigma 150-500mm HSM, 150mm MACRO HSM, Sigma 18-250 HSM, Sigma 10-20mm HSM mackloon Sold Items 7 05-01-2011 02:25 AM
Marrying a KX to a Sigma 150-500 Al_in_the_Shire Pentax DSLR Discussion 4 03-19-2010 07:29 AM
More Shot's with the Sigma 150-500 APO HSM Fl_Gulfer Pentax SLR Lens Discussion 4 02-12-2009 12:04 PM



All times are GMT -7. The time now is 11:21 PM. | 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