auto focus on 500d in movie mode

Hi we have been researching cameras and cases for a bit now, and we have been currently using a lumix fx35 for a cheap camera its been pretty good, but we want to upgrade to a dslr to get better stills

thing is we shoot videos and photos, and we were hoping that our new camera would continue to allow us to use one device for both functions so we have been looking at the canon 500d with a sea and sea housing but reading more about the camera it says you have to pretty much manually focus during movie mode, I also noticed that in any demos of the video from that camera, I have seen the camera is holding still

we do most of our video while freediving, and take video of freedivers, pelagic fish, sharks etc. Often both the subject and the shooter are both moving. It doesn't seem that manually focusing would be an option while moving around so much. I mean what could you do , try to manually manually focus, in between equalizations on the way down? all we are looking for is a dslr that can also match the video of our cheap fx35, is it pretty much a given that a dslr will not be able to refocus once it is recording a movie?

You can autofocus using the AF-ON button. You just can't do it WHILE recording.

You can autofocus using the AF-ON button. You just can't do it WHILE recording.

so if something swims up to the camera and the swims away it would only be in focus at the point when the video started?

QUOTE (Drew @ Feb 12 2010, 07:56 AM) You can autofocus using the AF-ON button. You just can't do it WHILE recording.

Yes you can while recording. But the autofocus is too slow and noisy to be usefull.

Autofocusing while taking video isn't really feasible.

You can, however, use the properties of the optics so that you have a large range in focus. For example, if you were to shoot video using a 5D MkII camera with a 17-40mm lens @ 17mm, you could use an aperture of f/8, and everything from 2.84 feet and further would be in focus. This means you could effectively focus before you start recording and almost everything would stay in focus.

Depth of field calculator: http://www.dofmaster.com/dofjs.html

Also have a look at this article: http://www.backscatter.com/5D2

Autofocusing while taking video isn't really feasible.

 

You can, however, use the properties of the optics so that you have a large range in focus. For example, if you were to shoot video using a 5D MkII camera with a 17-40mm lens @ 17mm, you could use an aperture of f/8, and everything from 2.84 feet and further would be in focus. This means you could effectively focus before you start recording and almost everything would stay in focus.

 

Depth of field calculator: http://www.dofmaster.com/dofjs.html

 

Also have a look at this article: http://www.backscatter.com/5D2

You can shoot wide and prefocus on something like your fins. And if you use these fins, Scubapro Novas, you can probably knock out your white balance while you're at it.

Yes you can while recording. But the autofocus is too slow and noisy to be usefull.

I should clarify that you can AF but it will not track a subject but acts like a one-shot or momentary AF. If the subject isn't contrasty enough, then you'll be recording the focus search, which to me may as well be not recording at all.

You'll find any autofocusing while shooting movies with an SLR means you record 2-5 seconds of the camera's autofocus searching desperately to locate and lock on a subject (and then when they move you have to do it again) it will have the same slow focus problems for you when using the "liveview" mode as well for shooting.

This is pretty typical for all SLR cameras with a liveview/ movie mode right now, to my understanding the only camera that has managed to get around this is the new top-of-the-line Sony SLR which has drastically improved their liveview technology and it is now almost an instant focus like using the viewfinder. Another year or two and the technology of the liveview/ movie mode on the SLR cameras will match an HD Camcorder but for now they are no substitution.

The technique posted by Ck/SF is pretty much the only way you can really do movies with your SLR. The sound is also complete crap unless you have an external mic (something that you can't add to a 500D).