AF.C in video mode

mlines · 07-14-2021, 01:23 PM

I have been playing with video and found that I am not able to select AF.C in video mode, it is disabled in the menu. This is with the kit 18-55mm lens. However if I put on the 55-300mm PLM zoom it does allow AF.C

The manual says that video af.c only works with certain lens but then does not appear to state what the criteria are.

I want to use a wider lens around of 18mm, does anyone know what the criteria is to make it work?

**Bob 256** · 07-14-2021, 01:35 PM

Actually, with that wide a lens, focusing may not be a big issue. If you use a moderate f-stop (say f8), you should be able to set the lens just short of infinity (manual focus) and leave it there. Unless you're trying to focus up close, an 18mm lens at f8 will be pretty sharp from a few feet out to infinity. A problem you'd encounter with AF is that it will have a hard time working with an 18mm lens and may actually hunt, thus causing issues. Manual focusing overcomes that as long as you have a good depth of field which 18mm can deliver. Of course, if you want to use a longer focal length, then focusing can become a necessity. I'm not sure what the AF.C limitations are for motion photography with the K-70.

mlines · 07-14-2021, 01:42 PM

It's a K-70.

The issue I have is that it's me I want to focus on so I cannot be in front and behind the camera at the same time. I tend to end up with soft focus all the time

**Bob 256** · 07-14-2021, 01:55 PM

One way to accomplish that is to use a separate off-camera monitor which you can see. That would allow you to focus while being the subject. You'd need a monitor of size and sharpness to meet the task.

swanlefitte · 07-14-2021, 02:41 PM

Your experience suggests only kaf4 lenses work. Just a guess.
There are only a few at present. The new top of the line lenses are all kaf4. The announced da*16-50 will have it but way more $$$ than a kit lens.

selfnoise · 07-14-2021, 02:44 PM

The 55-300 plm is the only lens that works with AFC. It's possible they might update the firmware when the 16-50 comes out but who knows.

**clackers** · 07-14-2021, 06:02 PM

Originally posted by mlines

I have been playing with video and found that I am not able to select AF.C in video mode, it is disabled in the menu. This is with the kit 18-55mm lens. However if I put on the 55-300mm PLM zoom it does allow AF.C

The manual says that video af.c only works with certain lens but then does not appear to state what the criteria are.

I want to use a wider lens around of 18mm, does anyone know what the criteria is to make it work?

The brand new DA*16-50 will be the second PLM lens, Mlines!

**clackers** · 07-14-2021, 06:06 PM

Originally posted by mlines

It's a K-70.

The issue I have is that it's me I want to focus on so I cannot be in front and behind the camera at the same time. I tend to end up with soft focus all the time

You prefocus, Mlines. You don't want focus to change repeatedly during a scene, anyway, it's awkward, like seeing a camera bob up and down handheld. You see amateur Youtubers where the focus racks in and out until it's happy!

Put anything on the chair beforehand, or if it's a standing scene, a tripod or similar.

Have you ever seen how a TV show or movie is made? There is tape on the floor for where the actors have to end up in a scene to be in focus. Professional production is manual focus, manual aperture. Nothing's left to chance.

07-14-2021, 01:23 PM	#1
mlines Forum Member Join Date: May 2018 Location: Berkshire Posts: 90	AF.C in video mode I have been playing with video and found that I am not able to select AF.C in video mode, it is disabled in the menu. This is with the kit 18-55mm lens. However if I put on the 55-300mm PLM zoom it does allow AF.C The manual says that video af.c only works with certain lens but then does not appear to state what the criteria are. I want to use a wider lens around of 18mm, does anyone know what the criteria is to make it work?

07-14-2021, 01:35 PM	#2
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,375	Actually, with that wide a lens, focusing may not be a big issue. If you use a moderate f-stop (say f8), you should be able to set the lens just short of infinity (manual focus) and leave it there. Unless you're trying to focus up close, an 18mm lens at f8 will be pretty sharp from a few feet out to infinity. A problem you'd encounter with AF is that it will have a hard time working with an 18mm lens and may actually hunt, thus causing issues. Manual focusing overcomes that as long as you have a good depth of field which 18mm can deliver. Of course, if you want to use a longer focal length, then focusing can become a necessity. I'm not sure what the AF.C limitations are for motion photography with the K-70. Last edited by Bob 256; 07-14-2021 at 01:42 PM.

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07-14-2021, 01:42 PM	#3
mlines Forum Member Join Date: May 2018 Location: Berkshire Posts: 90 Original Poster	It's a K-70. The issue I have is that it's me I want to focus on so I cannot be in front and behind the camera at the same time. I tend to end up with soft focus all the time

07-14-2021, 01:55 PM	#4
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,375	One way to accomplish that is to use a separate off-camera monitor which you can see. That would allow you to focus while being the subject. You'd need a monitor of size and sharpness to meet the task.

07-14-2021, 02:41 PM	#5
swanlefitte Pentaxian Join Date: May 2015 Location: Minneapolis Photos: Gallery Posts: 4,068	Your experience suggests only kaf4 lenses work. Just a guess. There are only a few at present. The new top of the line lenses are all kaf4. The announced da*16-50 will have it but way more $$$ than a kit lens.

07-14-2021, 02:44 PM	#6
selfnoise Senior Member Join Date: Apr 2008 Location: Westbrook, ME, USA Photos: Gallery Posts: 288	The 55-300 plm is the only lens that works with AFC. It's possible they might update the firmware when the 16-50 comes out but who knows.

07-14-2021, 06:02 PM	#7
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by mlines I have been playing with video and found that I am not able to select AF.C in video mode, it is disabled in the menu. This is with the kit 18-55mm lens. However if I put on the 55-300mm PLM zoom it does allow AF.C The manual says that video af.c only works with certain lens but then does not appear to state what the criteria are. I want to use a wider lens around of 18mm, does anyone know what the criteria is to make it work? The brand new DA*16-50 will be the second PLM lens, Mlines!

07-14-2021, 06:06 PM	#8
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by mlines It's a K-70. The issue I have is that it's me I want to focus on so I cannot be in front and behind the camera at the same time. I tend to end up with soft focus all the time You prefocus, Mlines. You don't want focus to change repeatedly during a scene, anyway, it's awkward, like seeing a camera bob up and down handheld. You see amateur Youtubers where the focus racks in and out until it's happy! Put anything on the chair beforehand, or if it's a standing scene, a tripod or similar. Have you ever seen how a TV show or movie is made? There is tape on the floor for where the actors have to end up in a scene to be in focus. Professional production is manual focus, manual aperture. Nothing's left to chance.