This review is part of my photo reference set on Flickr. Clicking the photo above will take you to the photo page on Flickr, with pretty much the same review, but very detailed notes about each lens on the photo itself.
I recently picked up the Voigtländer Ultron 40/2 (seen left, above) to use as my primary lens on the Pentax MX. Smaller lens to go with a smaller body, naturally. 43mm is the standard focal length for 135 format photography — not 50mm (blame the folks in Wetzlar for that one). My favorite standard range primes have always been in 40-45mm. With this in mind, my options for a small prime were basically the Ultron, the old Pentax 40/2.8 pancake, or the Pentax Limited 43/1.9. The Limited is a beautiful lens, and I still want to get one some day, but it doesn’t seem much smaller than a normal Pentax standard, and I simply can’t afford it. The 40/2.8 pancake demands high prices, but it’s not the sharpest thing in the world… I still want to get one some day, because it’s tiny, but not until I find a good deal.
The Ultron is larger than a pancake, but smaller than a standard Pentax prime. Feel of the focus is the best I have felt on any lens I have ever touched, hands down. Aperture is the same terrible combination of full- and half-stop clicks as a genuine Pentax lens. The aperture ring is a bit smooth, and takes some getting used to. Lens is solid and heavy; heavier than the Pentax 50/2. Image quality is excellent, the lens is insanely sharp edge-to-edge. It does exhibit more distortion than I would expect (at both the focal length and the price point), but this is generally not noticeable, and correctable in post.
A few final observations: The CV uses aspheric elements… I do not know if these are plastic, hybrid, or glass. I doubt glass, due to cost. I doubt plastic due to weight. So, I have to guess hybrid. CV only includes a Leica-sized lens cap, to go on the hood. This cap is incredibly thick, plus the addition of the hood, and your small lens just got considerably beefier. I use a slim Pentax (F?) edge-squeeze type cap instead. The CV has 9 curved aperture blades, which results in round bokeh at any setting. If you value sunstars over decent bokeh, I guess this lens isn’t for you — personally, I’ll take the bokeh. Speaking of bokeh, while it won’t look horrifically polygonal on this lens, it does get a little ringy and is not necessarily my favorite. Optical design is 6 elements (one aspheric) in 5 groups on the Ultron, 5 in 5 on the 50/2, 5 in 4 on the 40/2.8 pancake, and 7 in 6 on the 43/1.9 Limited.