Auto focus DSLR in video?

[NateNLogansDad]

I have a Nikon D5000 that does very nice video in my opinion (720) but if you zoom in or out it will not focus automatically. I'm assuming it's because the focus is in the lens and not the body. Is this correct? If so, would something like the D90 focus while recording and zooming in?

 

[Code]

Nope, it's not because the body doesn't have a focus motor, the D90 can't AF during recording either. The reason is that the mirror is flipped up during recording so the AF sensor can't be used.

On the Canon 500D and 5D Mark II you can push a button to do a one-off contrast-detection focus adjustment during recording, but it is jerky and the AF motor sound is picked up by the microphone.

The Panasonic GH1 is the only dSLR-like camera (not technically a dSLR because Micro 4/3 cameras have no mirror) that can do continuous AF during video recording at the moment, and its mic is separated from the camera body so it doesn't pick up AF noise. For now it's the only one that even comes close to replacing real camcorder functionality.

 

[Groucho]

Apparently the D300S can do autofocus during movie recording (though you're stuck with 720p/24 fps - sorry, I don't think less than 30 fps should really count!)...

DPReview has the following to say about it:

However, although movie mode still feels a little tacked-on, it is significantly improved over existing Nikon DSLRs. The biggest difference it that the camera can now use its contrast-detection autofocus system while shooting movies (by setting Liveview mode to 'Tripod'). We'd recommend using an external microphone if you're likely to use this features, since the noise of the camera or lens autofocusing can be heard on the movies. It's also worth noting that, even when using lenses with Nikon's ultrasonic AF-S motors, focusing isn't particularly snappy, so will have to be worked into videos as an 'effect,' rather than an annoyance.

I think they may have edited that, I could swear that when I read it when it was first posted, it was a bit harsher on the AF noise that was picked up, something about "grumbling and groaning"...

 

[zackiedawg]

Apparently the D300S can do autofocus during movie recording (though you're stuck with 720p/24 fps - sorry, I don't think less than 30 fps should really count!)...

Interesting you say that...most of the film-heads would say just the opposite - 24fps replicates film (movie) frame rate.

Though I agree - DSLR video is not ready for prime time yet - while it can look good with the DSLR's low light ability, shallow DOF, and creamy backgrounds, functionally it is a far cry, with bad sound, poor AF (or no AF), recording limits...not to mention that shallow DOF that looks good but is a lot harder to shoot with in a movie than folks think.

I'm of the 'keep video out of my DSLR' camp, though I know that's a losing battle...if eventually I have to buy a DSLR with it, I won't use it, mostly because I don't have any interest in shooting video. But I'm sure it's being worked on so that future DSLR video will be more properly functional and close the gap with video camera functionality.

 

[Groucho]

Interesting you say that...most of the film-heads would say just the opposite - 24fps replicates film (movie) frame rate.

24 fps is total nonsense IMHO. That is a spec that comes from hand-cranked cameras from 100 years ago! (Well, around 100; IIRC the hand-cranked standards were either 16 or 24 fps but I don't know when those "standards" were officially chosen, and I think most motorized movie cameras were almost always 24 fps.) Unless you are planning on converting your DSLR-created video to actual film and running it through a projector, 30 fps is a much more sensible choice because it will correctly match what virtually every playback device is designed to do. (Yes, some more advanced TVs can now correctly play back 24 fps thanks to film-sourced BluRays being correctly encoded at 24 fps not 30 like DVDs, but they will give smoother results at 30 fps.) I'm quite sure that the only reason the Nikons are doing 24 fps is because they don't have the video-specific horsepower to run at 30 fps. Their video capabilities came along a year or so after the K20D was able to produce 21 fps in jpgs; Nikon just went a hair faster and put in rudimentary sound and video encoding and they apparently haven't updated their video processing too much, with even the big-bucks D300S producing the same resolution and audio. (I say rudimentary as they only record 11 kHz, which is pretty low-fi - the other video-capable DSLRs do 44.1 kHz, which is CD quality. Of course, IMHO they ought to do 48 kHz, which is what DVDs are and PCs deal with that better, but oh well!)

Though I agree - DSLR video is not ready for prime time yet - while it can look good with the DSLR's low light ability, shallow DOF, and creamy backgrounds, functionally it is a far cry, with bad sound, poor AF (or no AF), recording limits...not to mention that shallow DOF that looks good but is a lot harder to shoot with in a movie than folks think.

I'm of the 'keep video out of my DSLR' camp, though I know that's a losing battle...if eventually I have to buy a DSLR with it, I won't use it, mostly because I don't have any interest in shooting video. But I'm sure it's being worked on so that future DSLR video will be more properly functional and close the gap with video camera functionality.

I don't mind it; in fact I'm kind of happy with it because I can take short videos of the kids (which is really about the only kind of video I take) without carrying along a full camcorder (which is overkill) or a PnS. Focusing is an extra step but modern 3" LCDs give nice feedback so it's not too bad, with a little practice, to get good results. (Of course, I'm partial to manual focus anyway, so there you go.) I even saw one guy who attached a full focus puller rig to a K-x to give you a big external crank to adjust focus with.

As for sound, on the 44.1 kHz ones with an external microphone, the sound can be quite good; as good as your mike at least.

 

[MarkBarbieri]

I won't say that 24fps is total nonsense, but it's close. Stuff filmed at 24fps looks different than stuff filmed at 30fps. Most filmmakers seem to think it looks better. My guess is that they are more accustomed to the look. Its similar to the way that people who grew up with tube amps prefer the sound of tube amps, even though it is less accurate. That's my take.

The other thing that makes 24fps nice is that much of the world uses 25 fps for their TV standard. It's easy to go from 24fps to 25fps. Going form 30fps to 25fps looks a bit dodgy. The US is 30fps. Europe is 25fps.

As for focusing, its hard. I have a semi-pro video camera with a separate dedicated focus port and it is still hard getting the focus right for HD stuff with relatively shallow DOF. Serious video shooters use an external high def monitor. They also pre-plan their focus points using magnification and peaking (sort of a B&W extreme contrast enhancement) to get the focus correct. They also have devices added to their lenses to give them more precise control over the focus and to allow them to present focus points. My advice is to use a really narrow aperture or to only shoot when the camera and subject aren't moving and you can make your focus precise.

As for audio on a DSLR, it sucks. Even with an external mic, I don't know of a DSLR that doesn't do auto-gain. Use an external audio recorder for your audio and use the audio on the DSLR for syncing.

Video on a DSLR isn't useless. It's actually really useful in two extremes. It's great for simple convenience shooting when you don't want to lug a video camera. It's also great for specialty video shooting when you want to do things that a regular video camera struggles with (shallow DOF and extreme low light).

I use mine as a B camera for school production shoots. I'm recording audio on a separate audio recorder, so I don't have to worry about the sucky sound. I'm shooting at a relatively static stage from a tripod, so I can lock down my focus. It has been a lifesaver to have an extra camera to use while my main camera is transitioning between shots.

 

[Groucho]

PAL is a whole different set of problems that I decided to ignore in my first reply... yes, you can play back 24fps at 25fps but you get a minor speed-up - movies are shorter and the audio pitch is higher. The change is not dramatic but it is definitely there. The usual 3:2 pulldown to go from 24 fps film to 29.97 fps NTSC is messy but at least the playback speed is accurate.

Fortunately many of these problems are starting to go away with modern HD equipment, where the movies are stored in the framerate that they were shot in and the playback device can display it accurately without too many tricks. This is nice for people like me who import a fair number of movies; with DVDs, you always had to deal with the PAL movies that were slightly off in terms of speed and sound. Ugh!

Ultimately, IMHO, video on a DSLR is about as handy as video on a PnS. Neither one will replace a proper camcorder but as long as your expectations are realistic, you can have fun with it.

 

[NateNLogansDad]

I want to keep quiet because I'd love for the conversation to keep going but I wanted to say I am listening

 

[MarkBarbieri]

yes, you can play back 24fps at 25fps but you get a minor speed-up - movies are shorter and the audio pitch is higher.

That's easy to correct is post production. The audio can be kept the same and the 24th frame an be shown twice. When done with even amateur video production software, the effect is virtually unnoticeable. Converting 30fps video to be shown at 25fps does work nearly as well.

Ultimately, IMHO, video on a DSLR is about as handy as video on a PnS. Neither one will replace a proper camcorder but as long as your expectations are realistic, you can have fun with it.

I definitely agree that a DSLR won't replace a video camera. It can, however, be a great supplement for special situations.

 

[Groucho]

Unfortunately, most DVDs don't do that, and there's really not a clean way to adjust the audio. Most PAL film-sourced DVDs are a victim of PAL speedup, so the movie runs 4% faster than it sound. Sometimes voices are pitch-corrected to be brought back down but the music is still sped up, which can be very distracting if you are used to the correct speed, then hearing it in a different key. You can tell by running times; most PAL movies will have shorter running times due to the speedup.

WinDVD has a Truspeed mode that is supposed to slow down the playback of PAL movies so that they play at the correct speed and audio pitch, if one wants to get things right... but it's probably easiest to stick with NTSC. On the other hand, the PAL discs have a slightly higher vertical resolution.

 

[DisneySuiteFreak]

I have a Nikon D5000 that does very nice video in my opinion (720) but if you zoom in or out it will not focus automatically. I'm assuming it's because the focus is in the lens and not the body. Is this correct? If so, would something like the D90 focus while recording and zooming in?

Honestly, I prefer the manual focus with nice creamy bokeh and excellent low light capabilities (that my regular 3CCD camcorder can only dream of achieving) to the AF hunting that occurs with said 3CCD camcorder in low light (think dark night clubs). I have an HD camera and even that tends to hunt for focus in low light situations. Much better to use manual focus, imo. It's not that hard; Just have to practice.