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Focus control while in video mode? (Read 3783 times)
MQ-VisualPursuit
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Focus control while in video mode?
03/16/10 at 12:32:11
 
Most of you will be aware that the new class of Full HD video capable DSLRs is used more and more for real production work. Lately, House, M.D. is
produced with EOS 5D MkII cameras.

However, focussing is a real issue while recording,
and most solutions rely on mechanical solutions.

But! The camera has focussing integrated in the lenses, so why not use OCC to send focussing commands to the camera?

OCC in video mode would need to be able to start/stop video recording and focus back/forth.

Do you guys think this is possible? Has
anybody tried it before?
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Blochi
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Re: Focus control while in video mode?
Reply #1 - 03/16/10 at 15:04:12
 
That's a really interesting idea.

Having a real graphical user interface for focus pulling could allow for setting markers, and even program smooth transitions from Marker A to B in X seconds....

But I think for this to work, it would require an additional USB connection. There's talk about how that can be done.

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Steve Chapman
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Re: Focus control while in video mode?
Reply #2 - 03/17/10 at 16:41:29
 
Wow. I didn't know that House uses 5D2's. That's remarkable. (I was going to say unlikely... Cheesy)

I understand Magic Lantern offers more focus control options?

I'm debating upgrading my 5D2 to the newest firmware. Has anyone done image quality tests using all of the firmware iterations? I have always suspected the highlight ghost correction that Canon added very early in production has had an effect on IQ.
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Castillonis
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Re: Focus control while in video mode?
Reply #3 - 04/13/10 at 04:29:05
 
The newer Canon cameras that shoot video such as the Canon 5D Mark II and the Canon 7D have two auto focus subsystems. 

Canon 7D review from DPreview.com
Read the first paragraph describing live view.
http://www.dpreview.com/reviews/canoneos7d/page9.asp

1. The regular auto focus subsystem is phase detection based.  Some of the light passes through the mirror and is refocused by concentrator lenses on a secondary sensor for autofocus.  There are two line sensors for each line in a focus point.  The brightness is compared and the direction and distance required to achieve focus is determined.  ( This is done without stopping down the diaphragm blades and lets as much light through as the maximum diameter will allow )

2.  The second focusing system is contrast based and uses the image sensor.  It is used for auto focus for video.

General link for Magic Lantern ( link to focus video below )
http://magiclantern.wikia.com/wiki/Magic_Lantern_Firmware_Wiki

The non official firmware enhancement Magic Lantern is capable of doing focus bracketing.
Demonstration of focus racking and focus stacking
http://magiclantern.wikia.com/wiki/Focus
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Castillonis
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Re: Focus control while in video mode?
Reply #4 - 04/13/10 at 04:39:23
 
1. The Canon SDK / DLLs that run on Windows or OSX that the Canon remote utility that talks PTP plus Canon proprietary extensions over USB is capable of changing the focus if you leave the lens in auto focus mode.

2. You can also do this with Breeze Systems DSLR remote Pro software.  You can automate control of the application using the freely available Autohotkey. Breeze Systems has some autohotkey example scripts that you can download for use with DSLR remote.
http://www.breezesys.com/DSLRRemotePro/
http://www.breezesys.com/DSLRRemotePro/focus_stacking.htm
http://www.autohotkey.com/
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