ND filters necessary for filmography at fixed f/2.2 with drone?

[paintingwithlight]

Hi all,

I recently purchased a Mavic Pro. I've been watching tutorial videos. The camera is a fixed f/2.2 so your variables are ISO and shutter speed. The tutorial videos I've watched indicate that if you want to produce a video at 30 frames per second (fps) then the capture frame rate should be at least twice that, or 60 fps. So far it all makes sense to me. However, next the claim is made that in order to get a smooth cinematographic look the frame rate should not be significantly higher than 60 fps, hence the need to use ND filters on a bright day. The idea is to have each frame slightly blurred so that the transition from frame to frame is not jarring. Would one really notice at a 30 fps rate if the images were each captured at, say, 1/2000 s? I don't feel like spending a few hundred dollars on ND filters as an experiment just to see...

Cheers

Michael

[Manfred M]

If you are shooting at 60 fps and play back at 30 fps your video will run at half speed. The cinematic look of feature films were shot at 24 fps. You should be shooting at whatever frame rate you are planning to play the video at. The 30 fps is usually associated with standard definition television in North America where the NTSC speed was 29.97 fps.

[dje]

I wonder if there might be some confusion in terminology here. I think when Michael refers to a "capture frame rate" of 60 fps he is probably referring to a shutter speed of 1/60 sec.

In the days of film cameras with rotating mechanical shutters, I believe it was common to have the shutter open for about half a rotation (ie half of the frame period) and at 24 fps this would give a slight blurring of motion.

I would say that the effect of shutter speed on video appearance depends on the amount of motion in the scene and also i suppose how much the camera is moving (on a drone). I have never shot using a drone but for general video shooting i don't get too hung up over shutter speed and am quite happy to use shutter speeds somewhat faster than the double the frame rate.

I suggest you do some tests with the higher shutter speeds to see how the video looks before investing in ND's. If you are shooting panoramic video with the drone it may not matter too much. Incidentally I assume the camera has auto exposure?

Dave

[Manfred M]

You could be right Dave. I have done a lot of video work with higher end video cameras and the discussions on the film-like look were centered around the points I made above. The timing issues of the rotating mechanical shutters were indeed more complex than the speed that the electronic shutters in modern video cameras use. Unfortunately I don't know how the shutters on the relatively low cost cameras like a drone or GoPro work. On higher end video cameras there is a degree of variability in shutter speed, but in addition to changing the aperture, these cameras will tend to have a turret fit with ND filters (0, 4, 16 and 64 stop densities) as well as a gain control (similar to ISO settings on a still camera) were used to control exposure.

[paintingwithlight]

Manfred and Dave,

Yes, by "capture rate" I should have said shutter speed. Presumably the reason for a shutter speed not to be less than 1/60 s when shooting 30 fps is because then one has 1/60 s to record the image and another 1/60 s to export the image to storage and ready itself for the next exposure?

Yes the Mavic Pro has a fixed FL, fixed aperture f/2.2 12 MP sensor. You can vary the shutter speed and the ISO. There are no built in ND filters. It can be shot in manual or auto mode for both focus and exposure. The "pros" whose videos I saw indicated a preference for manual focus and exposure when shooting video.

I suppose that you are right Dave - I should make a series of "high-speed" passes over a field of canola on a bright day at various heights and examine the resulting video.

[dje]

Presumably the reason for a shutter speed not to be less than 1/60 s when shooting 30 fps is because then one has 1/60 s to record the image and another 1/60 s to export the image to storage and ready itself for the next exposure?

Michael there is certainly some time required to read the captured frame from the sensor before the next frame capture starts and this time would depend on the camera to some extent. I shoot 50 fps progressive with my Sony a6000 and I find that as I reduce the shutter speed below 1/100 sec, at some point the camera starts skipping a frame capture eg it might record three frames and then just repeat the third frame to produce the fourth in the processed video. Interestingly this camera allows me to use a shutter speed slower than 1/50 sec when shooting 50fps but in this situation it starts repeating every second frame. It's worth experimenting!

Dave