Originally posted by C_Jones 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.