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.