Auto Focus, Auto Exposure?

[Mark Goodsell]

Does the auto focus work for video? If so, how well? Also same question concerning the exposure in video mode. Also how well. Obviously we would use manual most of the time, but just curious on the auto modes.

Thanks

[Bill Pryor]

You can press the auto focus button to focus before you shoot, but then you can't shift focus while shooting if you need to unless your lens lets you do it manually without switching the auto off. I don't know about any of the other auto stuff.

[Brian Luce]

It always hunts for focus when I try it. I don't even bother with it, unless it's a still shot of course.

[Andy Wilkinson]

When shooting video on the 7D you CAN re-activate autofocus - by pressing the 'AF-On' button on the back of the 7D - not a lot of people seem to know that as this "you can't autofocus" misconception has come up on other forums. We all know that once you start recording video the half-press of the shutter does not activate the autofocus any longer, and so most people assume that's that! In the UK we call this syndrome RTFM (I won't translate it!)

However, as rightly stated, you almost certainly will not want to do this as it will hunt in and out (and make a noise for a second) and so make the period it's re-focussing totally unusable. It's typically better to focus/refocus manually but sometimes I'll do this "AF-On push to re-focus technique" if I'm in a situation where I don't trust my ability to judge a critical focus on the tiny (i.e. difficult for HD video focus) screen. I'd rather loose a second of useable video as it hunts knowing that everything after that, in the still being recorded video clip, will be focussed accurately on the part of the frame I want (assuming I or the subject does not move too much subsequently).

So the "AF-On button push to re-focus technique" does have a value if you want to keep recording video and you know you'll cut/trim around the point of AF-On activation in editing/struggle with focus otherwise (e.g. when outside in bright sunlight and the screen is difficult to see). It's another clever feature of the 7D (there are so many on this great cam!) to be aware of although I accept many will ignore it and just do focus adjustments for video manually, as indeed I do most of the time.

[Manus Sweeney]

wow, i never knew that, as you say i think many people didnt know that! (dont have any AF lenses yet but really good info to have for the future)

[Liam Hall]

Originally Posted by Andy Wilkinson

When shooting video on the 7D you CAN re-activate autofocus - by pressing the 'AF-On' button on the back of the 7D

It's also worth noting that this feature is user definable and can be assigned to another button under custom controls.

[Bill Pryor]

While you can do it, it's not really feasible, so I consider it not do-able. Try it and you'll see what I mean.

[Scott Shama]

I use the button quite often and it works fine.. Like it's been stated though, I know I won't be using the footage while it focuses.

[Ron Chau]

I find it quicker to magnify and manual focus.

[Keith Moreau]

I actually deactivate the half-shutter button so I know when I press the shutter it doesn't try to focus, I just use the back button focus which is ergonomically located under the thumb.

I often do a push auto during a video shoot if I know I won't use that moment. I think stopping video, pushing magnify, manually focusing, starting video does take more effort but I do that too sometimes.

Problem is the video AF - live mode is kind of slow and hunts a lot. I'm not always sure it gets the focus right and it does ruin a couple of seconds of video.

[Zachary Mattson]

I made a slightly modified version of this guy's follow focus. It cost me a grand total of $2.44, and works great. I modified it a little so it can also be used on my 50mm 1.8. Took about 20 minutes to make.

Cheap follow focus DIY on Vimeo