Originally posted by jct us101 What is catch in focus exactly?
Catch-In-Focus aka Trap-Focus: It's the poor-person's AF. Or the manual-user's AF.
You enable it on your modern Pentax dSLR (it's a Custom Menu setting). You put a manual lens on the camera, or an AF lens with a bit of tinfoil to (safely) short-out some contacts (especially the 6-o'clock pin). If the manual lens doesn't have a shiny or wide base, you use a bit of tinfoil, or stick some thin metal tape on the base, or (if shooting closeups with an M42 lens) you use a flanged M42-PK adapter. Anything to short the pins. You set the AF mode to AF-S. Now you're ready.
You approach a subject. You hold the shutter down. Nothing happens. You keep holding the shutter down. You move in relation to the subject, or slowly twist the lens. At the moment the subject comes into (central) focus, the green-hex confirmation icon appears and the shutter trips. SNAP! Voila! A perfect shot!
Another application: You aim the camera and focus at a point where you expect the subject to appear, like a racer at the finish line or whatever. They come into focus. SNAP! Or you put the camera on a tripod, plug in a wired remote with a latch, set the drive mode to Continuous, aim the camera where you expect a subject to appear (like at a bird feeder or under a bath shower) and latch the remote. Whenever the subject comes into focus, SNAP!
The limitation: Since CIF only works with manual-focus lenses, or lenses with AF-MF switches set to MF, or AF lenses whose AF has been disabled with the tinfoil trick, you can't select AF points. No focus-and-recompose, no focus-off-center, no rule-of-thirds, none of that. Straight ahead, dead on, that's it.
Quote: I've seen this lens everywhere, from Micro Four Thirds cameras to Canon cameras, it seems as though everyone has one and has it adapted to their cameras. What mount was it originally made for though?
I've only seen the M42 version, which can be adapted to almost anything, but I've read that a native PK (manual aperture) version is also made. Check with your local Moskva Mafiya contact, I mean Russian optics supplier. It really is a splendid item.
NOTE: We've had discussions about 'normal' lenses. For 35/FF, 43mm is the frame diagonal and is thus 'normal', but most lensmakers produced 50-55mm glass as their standard lens. Pentax made a 58; Zeiss did, and the Helios is a Zeiss clone; but neither made large numbers of 58's. Most 58's by far are the Helios-44, which along with the Industar-50 was the standard lens on vast quantities of Russian (now FSU, Former Soviet Union) cameras. In the APS-C world, the equivalent is a 40mm.
And WHY was the Helios-44 so ubiquitous? A couple theories: They were easy and cheap to make. OR, they made for more intimate personal close-ups than a 50mm. OR, it allowed (or forced) the Commie masses to keep a greater distance from their subjects. Take your pick: economics, esthetics, or paranoia. You be the judge.