AF still causes exposure change with new manual firmware at DVinfo.net

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Old May 29th, 2009, 08:42 AM   #1
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AF still causes exposure change with new manual firmware

A little birdie tells me that the use of AF with the new manual operation firmware still causes the aperture to open up when you activate it, the same as with 1.07 firmware. This makes AF while shooting pretty useless unless you are at full aperture already.

Whilst there are a few other advantages to using a Canon EF lens for video it would seem AF while shooting is not one of them.

Hope to be proved wrong about this one, maybe there is a work around.

Dan
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Old May 29th, 2009, 09:24 AM   #2
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Dan,
5 minutes ago I discovered P.123 of the Mk II Manual ...

"Autofocusing during movie shooting is not recommended since it might momentarily throw the focus way off or change the exposure. If the AF mode has been set to [Quick Mode], AF is not possible even if you press the <AF-ON> button during movie shooting."

Who says thanks to Canon for that "sophistication"?

I would not have a shred of video if I had not used autofocus. For birdflight, manual focus is largely useless.

Fortunately, I only have the Mk II on hire for the weekend ...

Last edited by Brendan Marnell; May 29th, 2009 at 10:33 AM. Reason: correction
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Old May 29th, 2009, 12:00 PM   #3
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Personally, I expect Canon to release a new lens interface specification in the next year or two that will be based on the EOS system, but support video features, such as dynamic autofocus and electronic zoom. A new camera that supports that system would be able to use the new ($$$) lenses, as well as older ones. The new video lenses would also work on older EOS cameras, through the new features wouldn't be available.

At least, that would be the direction if I owned the company. ;)

Every indication is that Canon doesn't think much of the current autofocus system for video. My guess is that the little birdie told Dan the truth.
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Old May 29th, 2009, 12:42 PM   #4
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Jon

No change in the EOS mount is required - http://www.dvinfo.net/conf/1146994-post7.html

AF would be possible if Canon would/could use the system from the latest Alpha SLRs which works nicely in live view. Again this has nothing to do with the lens.

Dan
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Old May 29th, 2009, 12:48 PM   #5
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Quote:
Originally Posted by Dan Chung View Post
A little birdie tells me that the use of AF with the new manual operation firmware still causes the aperture to open up when you activate it, the same as with 1.07 firmware. This makes AF while shooting pretty useless unless you are at full aperture already.
Even the phase-detect autofocus systems only work at near full aperture (typically f/4 or faster), so it is not too surprising that the contrast based systems would also want a minimum depth-of-field for detecting changes.
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Old May 29th, 2009, 01:23 PM   #6
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That's cool that AF is lens independent. I still expect to see electronic zoom in a future EF revision.
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Old May 29th, 2009, 01:47 PM   #7
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I have never had a professional video lens with auto focus.

Except.

My current favorite camera EX3 standard lens does have it. It has an auto mode but I never use it. Non auto focus is seen as a great feature by most shooters I work with. I hear lots of editors moan about shooters that use auto iris and/or auto focus, you can always tell.

Auto focus has to many problems with moving images. If a bug flies through a shot lens can go out of focus, or if you are following a person it may shift focus unpredictably.

Focus pulling is an art and computers are lousy artists.
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Old May 29th, 2009, 02:08 PM   #8
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I agree that auto focus is of limited use. That said, an instantaneous focus button can be helpful, but then it needs to revert to full manual operation. It's nice if that button is on or near the lens.

The focus operation on the current set of lenses isn't really ideal for video, is it? First, they breathe. Second, the ring position isn't absolute with hard stops. It's possible to get out of sync with your follow focus marks. That means the focus ring should move during instantaneous autofocus in order to keep things in sync. None of the current Canon lenses work that way. Also, I've heard some complain about latency in Canon's focus-by-wire lenses (the 85mm f/1.2 in particular.)
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Old May 29th, 2009, 02:48 PM   #9
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Quote:
Originally Posted by Jon Fairhurst View Post
I agree that auto focus is of limited use. That said, an instantaneous focus button can be helpful, but then it needs to revert to full manual operation. It's nice if that button is on or near the lens.

The focus operation on the current set of lenses isn't really ideal for video, is it? First, they breathe. Second, the ring position isn't absolute with hard stops. It's possible to get out of sync with your follow focus marks. That means the focus ring should move during instantaneous autofocus in order to keep things in sync. None of the current Canon lenses work that way. Also, I've heard some complain about latency in Canon's focus-by-wire lenses (the 85mm f/1.2 in particular.)
Focus-by-wire lenses could never be used with follow focus. There needs to be a mechanical connection for accuracy.

Hard stops isn't a problem if your focus follower provides them. I'm in the process of choosing a follower at the moment and Indifocus seems to be the only one to advertise hard stops.
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Old May 30th, 2009, 02:30 PM   #10
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Something tells me the chip in the 5D2 is not fast enough to be both encoding h.264 video and constantly analyzing sensor information for stable / fast auto focus.
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Old May 30th, 2009, 05:58 PM   #11
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Quote:
Originally Posted by Jon Fairhurst View Post
I agree that auto focus is of limited use. That said, an instantaneous focus button can be helpful, but then it needs to revert to full manual operation. It's nice if that button is on or near the lens.

The focus operation on the current set of lenses isn't really ideal for video, is it? First, they breathe. Second, the ring position isn't absolute with hard stops. It's possible to get out of sync with your follow focus marks. That means the focus ring should move during instantaneous autofocus in order to keep things in sync. None of the current Canon lenses work that way. Also, I've heard some complain about latency in Canon's focus-by-wire lenses (the 85mm f/1.2 in particular.)
Totally agree with this view. That a a quick auto focus would be useful but full auto focus would not. The only time I've ever used auto focus is when the camera I'm using has such terrible monitoring that you just can't tell what is in focus or not. In some ways the Canon is a bit like this as only being able to use the rear LCD screen makes it extremely difficult to see critical focus most of the time. Using the zoom in button helps a lot but obviously can't be used during shooting. Maybe the Zacuto Z-Finder rig is good enough?

FWIW We have done focus pulls with marks and they haven't slipped out of sync at all. So maybe it's the lens dependant?

Either way I don't see this as much of an issue.
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Old May 30th, 2009, 06:43 PM   #12
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Totally agree with this view. That a a quick auto focus would be useful but full auto focus would not.
Sean, for narrative shooting I would agree with you. But if you shoot a lot of moving subjects then a proper AF system (not like the 5dmkII) can really help, expecially if they are coming towards the camera fast or moving in an erratic way that makes manual pulling hard. This feature has already made it into Canon's very top end broadcast superzoom lens for Formula 1 etc Canon BCTV Lenses: HDgc Lenses: DIGISUPER 100AF

I daily use a functionning quick AF before shooting would be more useful as you say.

Dan
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Old May 30th, 2009, 06:49 PM   #13
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Focus-by-wire lenses could never be used with follow focus. There needs to be a mechanical connection for accuracy.
Mark,

Actually sort of not true, ultimately focus by wire can be more accurate than any manual pulling method. What needs to happen is for a focus pull device to be made that accesses the camera directly and instructs the lens to focus at precise distances. Canon's remote software already allows focus control to a connected computer but it can't do a smooth focus pull, somebody clever could probably programme this though. This system would work very much like the system on the Sony EX-1.

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Old May 30th, 2009, 06:52 PM   #14
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No need for autofocus

In 15 years of shooting video I have never had (nor wish to have) an autofocus lens. Autofocus and auto iris are sure signs of amateur shooting. Grab yourself a decent follow focus and make marks. Or better yet, get a loop and learn the range of your lens so you can instinctually pull on the fly.

-dave
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Old May 30th, 2009, 07:03 PM   #15
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In 15 years of shooting video I have never had (nor wish to have) an autofocus lens. Autofocus and auto iris are sure signs of amateur shooting. Grab yourself a decent follow focus and make marks. Or better yet, get a loop and learn the range of your lens so you can instinctually pull on the fly.

-dave
Dave,

I would generally agree with you. All my work to date has been with MF lenses and I use a Redrockmicro FF a lot of the time. I was also to my knowledge the first person to use a loupe and have spent a lot of time learning to pull on the fly. However, AF would have some real advantages if implemented properly, just check out the latest Sony Alpha SLRs use of live view AF to see what I mean by properly. If you are shooting news or sports where movement is unpredicatable then there may be many times where AF would be a sensible option, that's why Canon have added it to the monster lens in the link above.

Dan
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