[Wingincamera]

I have had three different Pentax cameras but have never checked out the CIF function. I just acquired the DA*55/1.4 lens which has a manual/auto switch on the lens so I thought I would finally try the CIF out. I was really impressed with the accuracy of this method. My target was a little glass ball hanging on a string. The ball is about 5/8" in diameter. I stood about three feet from it and focused the lens, then backed about eight feet away and using CIF just started walking toward the ball keeping it in the focus point. I was using the viewfinder.

[SSGGeezer]

Cool, I was trying it when having to focus manually on a dragonfly today but turned it off so I could control when the shot was taken. I do need to use it with my manual lenses.

[stevebrot]

I was really impressed with the accuracy of this method.

The accuracy and precision of Catch-in-focus (aka Focus Trapping) is the same as regular PDAF and works well as long as the subject or camera don't move too much after focus is detected. Historically, it was a happy coincidence where Pentax users (and presumably users of other brands) noticed that AF-S could be leveraged to trap a shutter release with manual focus lenses based on whether the AF system detected an in-focus event. The gating action of AF-S (no exposure if not in focus) was the key due to a "logic hole" that where the code also enforced the flip side of the case (always do exposure if focus is detected). This was back in 2007 when I was new to Pentax and also to Pentax Forums and knowledge of the feature was shared on this forum and other places on the Web. On the K-7, the feature became a custom menu setting (default = off) and so it has remained ever since.


Steve

[jpipg]

I love CIF but I do wish that it could be done on AF points other than centre. I’ve always found it fairly accurate and it’s very useful for action shots, with a little prefocussing.

[Wingincamera]

One of the things that surprised me was the KP able to obtain the focus since I was walking toward the glass ball while holding the camera with only my right hand. There was a lot of camera movement. I should explain I am recovering from rotator cup surgery on my left shoulder, so not at my best.
Camera settings were Pentax KP, lens DA*55/1.4 at 1/250, F3.5 iso 100. I love the bokeh of this lens.

Here is a crop shot:

[SSGGeezer]

I used CIF a few times today while I had my cheapo Rikenon 50mm F/2 on my KP. It doesn't resolve as well as my DA's but I still like the rendering on flowers and vegetation.

[stevebrot]

One of the things that surprised me was the KP able to obtain the focus since I was walking toward the glass ball while holding the camera with only my right hand.

If focus is attained, the shutter is trapped. Those are the rules. See this thread for an example of a camera that takes hummingbird photos nonstop day after day using CIF.

Pentax durability - PentaxForums.com


Steve

[acoufap]

I love CIF but I do wish that it could be done on AF points other than centre. I’ve always found it fairly accurate and it’s very useful for action shots, with a little prefocussing.

I also think it‘s a nice feature and wonder if it could be developed further so that we can preselect a focus point other than the center point.

This really would be helpful when working with fixed focus, framing with focus not on center and triggering the shutter by body movement.

I often use the function with M1.7/50 and M2.8/28.

[Ronald Oakes]

I used CIF a few times today while I had my cheapo Rikenon 50mm F/2 on my KP. It doesn't resolve as well as my DA's but I still like the rendering on flowers and vegetation.

Off the subject....that Ricoh Rikenon 50mm f2 lens can be quite sharp if you have a good copy. I wont get rid of my $8 copy !