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05-09-2020, 06:10 AM   #1
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Sigma 2X-Pentax 150-450 combo working on K1ii, not on K3, why?

I have been experimenting with combinations of my long lenses, multipliers and bodies, and I came across this strange behavior. The newest K1ii happily shoots (in manual focus) with the Sigma 2X-Pentax 150-450, while the K3 refuses to show focus indicator or shoot. I also cannot change the settings because the screen appears for a split second and disappears, any Idea? In principle should be the reverse, the oldest working and the newer not. Just to show what the combo can do on the K1, here is a moon picture taken with it, multiplying magnification by 1.5 using the center of the image is an attractive proposition

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05-09-2020, 01:46 PM - 1 Like   #2
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Which Sigma 2x are you using? I know my Sigma EX 2x can be very fussy about what it will and won't work with ... I've put it down to slight design variation on Sigma's part, for undisclosed reasons. I've since acquired a Kenko Pz-AF 2x which seems to be universally compatible, so it's no longer an issue.
05-12-2020, 01:18 PM   #3
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I am surprised it can be the 2x, which indeed is an EX which I bought together with the 70-200 f2.8. I rather thought it might be the body, is there any electronics in the multiplier? What for?
05-12-2020, 01:51 PM - 1 Like   #4
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i have owned 2 sigma EX 2 x teleconverters, the first one was a straight EX bought with the film version of the APO 70-200/2.8 EX lens, later this was updated for a very short run with DG coatings, but optically arguably the sharpest of all the sigma 70-200/2.8 zooms especially the early macro and OS ones. over time the contacts became intermittent, and i ultimately dropped this with the 70-200/2.8 attached (the lens hood cracked) and also the lens mount of the TC bent such that the contacts never mated again.

i replaced it with the later DG version of the same TC.

one thing i would question is attached to the pentax 150-450/5.6 lens whether the combination is too slow at F11 to get focus confirmation . this can vary from camera to camera type especially.

so it could either be a worn / slightly bent mount on the TC or slightly intermittent contacts, or it could be the K3 is not capable of giving focus confirmation at F11 native aperture. Try rotating around the lens axis on the free play of the lens locking.

05-12-2020, 03:14 PM   #5
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QuoteOriginally posted by maurizm Quote
I am surprised it can be the 2x, which indeed is an EX which I bought together with the 70-200 f2.8. I rather thought it might be the body, is there any electronics in the multiplier? What for?
That's the same combo as I've got, and they still live "as a pair", but Sigma's own paperwork for their 150-500mm specifically excludes this 2x from the compatibility list! There's no electronics in the 2x, so the SR in the camera can never compensate for the extra focal length, there's no power contacts, so it's screw-drive a/f only, and there's something just a little bit weird about the locking pin (release latch) which means it doesn't lock onto some lenses ... all in all a bit of a non-starter except for what it was designed for! Also be aware, due to the unusual placement of the optics within the 2x that some lenses will actually clash "glass on glass" if you try to mount them!
05-12-2020, 05:10 PM   #6
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QuoteOriginally posted by kypfer Quote
That's the same combo as I've got, and they still live "as a pair", but Sigma's own paperwork for their 150-500mm specifically excludes this 2x from the compatibility list! There's no electronics in the 2x, so the SR in the camera can never compensate for the extra focal length, there's no power contacts, so it's screw-drive a/f only, and there's something just a little bit weird about the locking pin (release latch) which means it doesn't lock onto some lenses ... all in all a bit of a non-starter except for what it was designed for! Also be aware, due to the unusual placement of the optics within the 2x that some lenses will actually clash "glass on glass" if you try to mount them!
There is a second issue with the sigma EX TCs. Specifically the front element extends into the lens barrel. The rear lens barrel must ge something like 30-35mm in diameter, and the element recessed a minimum of 15 mm if memory serves me correctly.

Also, as I noted in a previous post, compatibility also includes the ability to AF with the lens.

There is no electronics in the lens, just straight through contacts. Not even correct aperture for the TC magnification, so flash is under exposed unless you modify flash compensation
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