14 -140 auto focus tips?

F

Framerate

Well-known member
Hi, I'm getting to grips with my new GH1 - my main problem is the focus speed of the kit lens.

It's snappy enough focussing for still images, but when used in video mode it become quite lethargic - occasionaly it even goes om strike and refuses to focus altogether :angry:

When this occurs, I bring it into focus via the shutter button. In fact, continuously holding the shutter button down while videoing seems to help it no end - but that's hardly a practical work-around.

I've enabled all the focus assist related menu items I could find, without result. It's accurate - but slow.

Any tips/hints/tricks? - or is relatively lazy AF performance par for the course?

TIA
 
Part of the reason for the apparently slow AF may be by design. AF for video has to work a little slower, because instant refocusing doesn't look good on video. The camera can't wildly shift the focus around to find the right focus, like it does to find focus for still images, because that would make viewers nauseous.

Most pro videographers don't even bother using AF. They stay in MF because if the camera can't decide where to focus, the video shifts focus rapidly with horrendeous results.

That being said, I find AF occasionally useful. What I do when I do want to use AF (mostly for run-and-gun productions where I need to move a lot and shift subjects constantly) is set the camera to AFS, set the menu option "AF/AE lock" to "AF" and the menu option of "AF/AE Hold" to "On". Then, before you start recording, hit the AF lock button. The camera will autofocus to our subject then lock that focus in for the recording. If you push the AF/AE lock button again while recording, AF will resume, which I don't recommend. Also enable "AF+MF" in the menu; that way, when you tell the camera to focus and lock the focus, you can still adjust it manually with the focus ring, while keeping the focus locked and the camera in AFS mode.

Assuming you have the settings set how I described them above, and you turn off AF lock, you can still hold the shutter release halfway down to AF while you're setting up the shot.
 
CColton said:
Part of the reason for the apparently slow AF may be by design. AF for video has to work a little slower, because instant refocusing doesn't look good on video. The camera can't wildly shift the focus around to find the right focus, like it does to find focus for still images, because that would make viewers nauseous.
Click to expand...

Yes, I can understand that - how does the G2 get on with its predictive AF?


CColton said:
What I do when I do want to use AF (mostly for run-and-gun productions where I need to move a lot and shift subjects constantly) is set the camera to AFS, set the menu option "AF/AE lock" to "AF" and the menu option of "AF/AE Hold" to "On". Then, before you start recording, hit the AF lock button. The camera will autofocus to our subject then lock that focus in for the recording. If you push the AF/AE lock button again while recording, AF will resume, which I don't recommend. Also enable "AF+MF" in the menu; that way, when you tell the camera to focus and lock the focus, you can still adjust it manually with the focus ring, while keeping the focus locked and the camera in AFS mode.
Click to expand...

Thanks for the tip - the immediate problem would be the loss of AE lock, which despite the 14-140's much vaunted step-less aperure, I find pretty essential to avoid rapid fluctuations in light. Unless there's a way to lock AF *and* AE?
 
This has pretty much been the case with every video camera I've ever used. But on normal 1/3" or 1/4" prosumer video cameras, the DOF is so great, that you often don't notice how far off your focus is in auto.

However, I love the auto-focus on the GH1...it's FAST if you use half-press then switch to MF BEFORE you start recording. BUT...this limits you to a single focus plane for the entire scene. If you want to change, you have to half-press again...and edit that part out....or stop recording when focusing.

If you want to "follow" a subject through the scene with the focus, or rack back and forth, you'll need a lot of practice (and a manual lens would help), or get a follow focus setup to make it easier.

The "face detection" on the GH1 works pretty well tracking faces, but I find that the focus doesn't keep up with the face detection all that well when shooting video. I've only tried it a couple of times with a couple of lenses, but will do some more tests with it in the future. The theory of face dection working as well as a follow focus is just so darned awesome...although it still wouldn't allow racking back and forth between faces at different focal lengths. :)
 
swyzlstyx said:
If you want to change, you have to half-press again...and edit that part out....or stop recording when focusing.
Click to expand...

Have you found a reliable way to focus by half-pressing, and then keep it from trying to autofocus? I didn't think you could half-press focus in full manual.
 
CColton said:
Have you found a reliable way to focus by half-pressing, and then keep it from trying to autofocus? I didn't think you could half-press focus in full manual.
Click to expand...
I think switching to AFS, plus enabling AF Lock will allow you to accomplish that. I'm using a wired shutter release, BTW, to remove jitters from half-pressing shutter release button on camera body.
 
CColton said:
Have you found a reliable way to focus by half-pressing, and then keep it from trying to autofocus? I didn't think you could half-press focus in full manual.
Click to expand...

I've not experimented with the focus lock feature. My technique since noticing that the 'auto focus single' didn't 'stick' in video, was to half-press the shutter release, get a 'focus' on the object of my interest, then switch the focus option knob to 'manual', thus locking the focus at that point.

This doesn't work to well for 'event' coverage where the subject changes dynamically, but is good for static, or 'slow moving events', such as turtle races.
 
j1clark@ucsd.edu said:
I've not experimented with the focus lock feature. My technique since noticing that the 'auto focus single' didn't 'stick' in video, was to half-press the shutter release, get a 'focus' on the object of my interest, then switch the focus option knob to 'manual', thus locking the focus at that point.

This doesn't work to well for 'event' coverage where the subject changes dynamically, but is good for static, or 'slow moving events', such as turtle races.
Click to expand...

Focusing with that method would definitely be the safest option. Once you're recording you can still manually adjust the focus as you see fit.
 
Framerate;2098748 Unless there's a way to lock AF *and* AE?[/quote said:
Well - that was a daft question, wasn't it? :laugh:

It just goes to prove that, while real men don't read manuals, the even *more* real ones don't even look properly at the menu options.

(ashamed)
Click to expand...
 
Framerate said:
Well - that was a daft question, wasn't it? :laugh:

It just goes to prove that, while real men don't read manuals, the even *more* real ones don't even look properly at the menu options.

(ashamed)
Click to expand...

Well done! ;)
Don't worry, I only read the manual when I can't figure it out otherwise. A bad policy to operate under, admittedly.
 
You must log in or register to reply here.
Back
Top