This link takes us to the Pentax page:

http://www.jessops.com/directory/pentax-shop.aspx

Welcome aboard, PentaxUK!

It's off topic though, as we are are what we are. Not sure about the idea of simply those who sound most convincing deciding the value of things, that's self-perpetuating and leads to those who shout loudest and most convincingly drowning out what could be a more correct but more quietly expressed answer.

However, let's not stray into that area as it's nothing to do with Catch In Focus.

It's probably easiest to imagine something like a hedge, flat on to the camera, say 30 feet away. Defocus the hedge but move the focusing ring to a point closer, say 10 feet away.

Now let your model walk into the shot. When he or she reaches the point of focus, the camera will fire, and your model will be about 10 feet away when that happens.

Something like that!

Unfortunately there is often not a "definitive answer" and this is a forum for discussion....so people discuss what takes their fancy.

What I do think is that I spend most of my time shooting images, not fiddling to make things work. If I want to use CIF I use a manual focus lens. The right tool for the job.

You have a point ChrisA, but I was only mentioning in the context that most users won't really care and probably have never used the feature. I wasn't defending a prnciple of accepting everything that happens!

The trouble is that simple questions tend to go off on wild tangents that don't help the simple, straightforward question. It can confuse.

I suppose it would be nice if we started a new thread once it gets more esoteric in its appeal, but I doubt that will happen.

Isn't it much easier to just follow the instructions? I know some love to make things work where they "shouldn't" work, but for the majority of users that isn't really relevant.

It's a useful, but minor, feature that's available on all the Pentax DSLRs I've used, and it's a consequence of how things work, rather than the raison d'etre.

Yes, you have an early Super Takumar Model I that shares the "wrong way" aperture ring with the doicumented f2 version. I've never seen one of those before and I would imagine it dates from 1962-ish.

Alternatively, it's a late Auto Takumar with the first of the Super Takumar labels attached.

In other words, some hybrid version close to a change-over point?

You're missing the point. The camera only detects the point of focus when its AF system is switched on. Switch it off and you can only use MF, obviously.

There are very few Pentax lenses that run the "wrong way" but some do exist.

Can you post a picture of the Super Takumar 55/1.8 as this seems rather unusual? Are you sure it's not an Auto-Takumar?