Kern-Paillard Switar 25mm f1.5 AR on Pentax Q

The Switar 25mm f1.5 is one of those stupid mistakes that I sometimes made with too much assumption.  This lens has an AR designation which means the lens register is slightly shorter than the standard c-mount, though the mount itself is the same.  The lens goes further into the camera than a standard c-mount lens does and it would hit the frame area of the sensor on the NEX or M4/3 and would not go further in.  This prevents the lens from focusing to infinity. Out of desperation, sawed off a small part of the rear of the lens, hoping to make it focus to infinity, but to no avail, though it can now focus further than before.

The Pentax Q has an even short lens to sensor register than the NEX system, allowing more space between lens and sensor for lenses other than those with native Pentax Q mount. This AR 25mm f1.5 works perfectly on the Q with infinity focus.  Since the Q has a 5.5x multiplier, a 25mm lens would become a  137.5mm!  Sure, it's great for telephoto shots, but a pain to obtain any wide angle lenses.  Imagine a 100mm lens, when mounted on the Q becomes a 550mm, which makes most lenses with focus length > 50mm difficult to handhold.  The in-body image stabilization works, but not as effectively as lens based. I briefly tried the Kern-Paillard 75mm f1.9 lens on the Q and it was just too long for practical use.

The Switar AR 25mm f1.5 has typical quality of most Switar lenses, and very similar to the Switar 25mm f.4 that I used. Excellent even wide open, and has pleasing rendering of pictures.  On the Q, there is no vignetting, of course, and the blurred corners are significantly less than that on M4/3 or NEX, because only the small center area of the lens is used. Focusing the lens is painful, especially if you are used to an EVF.  The focus peeking feature on the Q is nowhere as good as the one on Sony NEX.  On the Q, the contrast is set sky high to simulate focus peeking, unlike the NEX cameras, where a colour is displayed for the in-focus portion. I find it very frustrating and difficult to get critical focus. Consequently, I turned this what should be a very useful feature off.

In terms of usability for manual focus lenses, the Q is simply not in the same league as the NEX cameras with focus peeking/EVF, but usable.

Lines - Pentax Q & Kern-Paillard Switar 25mm f1.5. Click for larger.

Lion - Pentax Q & Kern-Paillard Switar 25mm f1.5. Click for larger.

Barb Wires - Pentax Q & Kern-Paillard Switar 25mm f1.5. @ f1.5. Click for larger.