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01-21-2015, 04:35 PM   #1
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K5IIs, K Mount Sigma 150-500 and Pentax 1.4 Teleconverter Compatibility

Hi,

I doubt if I will ever buy a teleconverter, but was curious about if the Pentax 1.4 Teleconverter (rear converter), which is now available from Pentax, would be compatible with my Pentax K5IIs and Sigma 150-500 K Mount telephoto lens that I have. I really get great performance with the camera and lens already, but since Sigma does not make the 150-600 available in Pentax K Mount, I wanted to get some real Pentax user opinions on whether the newest Pentax 1.4 rear converter option is credible without losing significant autofocus capability, sharpness or F-stop availability. Also I wanted to find out if it could possibly harm my camera or lens due to some sort of structure issue, such as unwanted lens glass contact during attachment or use. My lens is K mount, and on the other hand it is Sigma, which I try to assume would be fully compatible in the way the Pentax K mount lenses are, but I would like to avoid any technical issue when caring for my equipment and its performance by finding out real compatibility specifications.

I know this a DSLR forum area, but this is having to do with my K5IIs and its accessory compatibility.

Thanks ahead of time for any information. I appreciate it.

01-21-2015, 04:45 PM - 1 Like   #2
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QuoteOriginally posted by C_Jones Quote
Hi,

I doubt if I will ever buy a teleconverter, but was curious about if the Pentax 1.4 Teleconverter (rear converter), which is now available from Pentax, would be compatible with my Pentax K5IIs and Sigma 150-500 K Mount telephoto lens that I have. I really get great performance with the camera and lens already, but since Sigma does not make the 150-600 available in Pentax K Mount, I wanted to get some real Pentax user opinions on whether the newest Pentax 1.4 rear converter option is credible without losing significant autofocus capability, sharpness or F-stop availability. Also I wanted to find out if it could possibly harm my camera or lens due to some sort of structure issue, such as unwanted lens glass contact during attachment or use. My lens is K mount, and on the other hand it is Sigma, which I try to assume would be fully compatible in the way the Pentax K mount lenses are, but I would like to avoid any technical issue when caring for my equipment and its performance by finding out real compatibility specifications.

I know this a DSLR forum area, but this is having to do with my K5IIs and its accessory compatibility.

Thanks ahead of time for any information. I appreciate it.
I don't see why it wouldn't work as far as optics go, but getting it to autofocus reliably would be another story. Pentax doesn't recommend lenses slower than F4 and since the Sigma is F5-6.3, your camera will almost certainly struggle to autofocus, even at the short end. I've tried the TC on the 18-135mm and outside of live view, the AF was really bad at 70mm (F4.5) and above.

A more viable option IMO would be to upgrade the K-5 IIs to a K-3, as the added megapixels will let you crop much more liberally. The price to upgrade the camera is actually about the same if not lower than getting the TC

Adam
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01-21-2015, 05:07 PM   #3
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I agree with Adam but I would also add that I am finding the Sigma 150-500 one of the easier to manually focus of my long lenses. The 1.4x would make AF uncertain but don't forget that you can always MF the lens.
01-21-2015, 05:29 PM   #4
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I found it easy to manually focus the 150-500 with the Q10. Focus peaking worked well. No reason it shouldn't work equally as well with the K-3. What I need for the Q10 is a heavier tripod.

01-21-2015, 05:36 PM   #5
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QuoteOriginally posted by boriscleto Quote
I found it easy to manually focus the 150-500 with the Q10. Focus peaking worked well. No reason it shouldn't work equally as well with the K-3. What I need for the Q10 is a heavier tripod.
Definitely with that magnification. I haven't tried the 150-500 on the Q but I have tried my telescope (1150mm on the K5) and a REALLY solid tripod is an absolute necessity IMHO.
01-21-2015, 06:37 PM   #6
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You'll also get focus peaking with the K3. I must try it! I haven't tried any lenses other than the DA*300 with the 1.4TC so far; I have a mirror lens I'd like to try with focus peaking.
01-22-2015, 10:33 AM   #7
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Original Poster
QuoteOriginally posted by C_Jones Quote
Hi,

I doubt if I will ever buy a teleconverter, but was curious about if the Pentax 1.4 Teleconverter (rear converter), which is now available from Pentax, would be compatible with my Pentax K5IIs and Sigma 150-500 K Mount telephoto lens that I have. I really get great performance with the camera and lens already, but since Sigma does not make the 150-600 available in Pentax K Mount, I wanted to get some real Pentax user opinions on whether the newest Pentax 1.4 rear converter option is credible without losing significant autofocus capability, sharpness or F-stop availability. Also I wanted to find out if it could possibly harm my camera or lens due to some sort of structure issue, such as unwanted lens glass contact during attachment or use. My lens is K mount, and on the other hand it is Sigma, which I try to assume would be fully compatible in the way the Pentax K mount lenses are, but I would like to avoid any technical issue when caring for my equipment and its performance by finding out real compatibility specifications.

I know this a DSLR forum area, but this is having to do with my K5IIs and its accessory compatibility.

Thanks ahead of time for any information. I appreciate it.
Thank you for your feedback Adam.

---------- Post added 01-22-15 at 01:17 PM ----------

The AF effectivity and image quality retainment were factors that I was most concerned with. Per some reviews I had seen prior to buying my K5IIs, it had better reviews than the K3, even in reference to image quality and crop situations in some instances. DxOMark has given the K5IIs a higher rating than the K3, though the K3 has some new and improved features that the K5IIs does not have.

I appreciate all of your feedback, and find it helpful. I suppose that only a person with my equipment setup I have now plus the converter would have information on actual results of use. I have seen answers on Amazon that say the combination is effective. Sigma did not offer their new 150 - 600 in the Pentax mount and Pentax does not offer a lens with that 150-600 range either, so I was just looking for viable options. I may just stick with what I have unless something within effective reason becomes available on the market. If in fact Pentax has not yet, it might have been a considerate move to construct the converter to be compatible with all of the functions of the K mount lenses if possible, such as the Sigma 150-500 for Pentax K mount. My K5IIs does great with the lens without the converter, I just wanted to weigh other possibilities. Also I have read that converters can reduce image quality, so that is another reason I may not take the chance.

Thanks.

Last edited by C_Jones; 01-22-2015 at 06:49 PM.
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