Mechanical/Rolling Shutter Tests

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First, let me clarify -- my intent here is to just present facts (and perhaps cut through some of DJI's marketing and general internet hype that preceded the P4p's release). It's not to bash on the Phantom 4 Pro. Despite the issues, I think it's still a significant upgrade over the standard p4 in terms of image/video quality and features.

Now, some tests to determine how bad the rolling shutter is during pans. I tested using an extreme case (spinning the drone around at full speed) at 24fps, 60fps and 120fps using h.264 and h.265. The 60fps/120fps footage was slowed down to conform to 24fps timeline, which is why it appears the craft is spinning slower (it's not).


Conclusion? Rolling shutter effects are obvious, especially in the 24fps footage. Vertical lines bend, where they should be straight. This indicates the mechanical shutter isn't being used for video. Rolling shutter is less obvious at 60fps and 120fps, likely because the entire sensor isn't being read -- DJI does 60fps and 120fps by line skipping.
 
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I can't seem to play the video but... is that a reasonable test? What if you spun a professional camera at that speed?
 
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First, let me clarify -- my intent here is to just present facts (and perhaps cut through some of DJI's marketing and general internet hype that preceded the P4p's release). It's not to bash on the Phantom 4 Pro. Despite the issues, I think it's still a significant upgrade over the standard p4 in terms of image/video quality and features.

Now, some tests to determine how bad the rolling shutter is during pans. I tested using an extreme case (spinning the drone around at full speed) at 24fps, 60fps and 120fps using h.264 and h.265. The 60fps/120fps footage was slowed down to conform to 24fps timeline, which is why it appears the craft is spinning slower (it's not).


Conclusion? Rolling shutter effects are obvious, especially in the 24fps footage. Vertical lines bend, where they should be straight. This indicates the mechanical shutter isn't being used for video. Rolling shutter is less obvious at 60fps and 120fps, likely because the entire sensor isn't being read -- DJI does 60fps and 120fps by line skipping.

Yeah, I didn't quite see how they could do a mechanical shutter for video -- for stills sure, but for video ... I don't think so. A mechanical shutter for a sensor of 1 inch would be fairly large and therefore require a substantial movement at least 30 times a second. A typical DSLR will have a shutter lifetime rating around about 200K actuation's which would last less than 2 hours at 30fps.

The mechanical shutter on DSLR's and Mirrorless cameras are, to the best of my knowledge, only used for stills.


Brian
 
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I can't seem to play the video but... is that a reasonable test? What if you spun a professional camera at that speed?
Video link should be fixed now -- youtube was still processing.

If the professional camera had a global shutter (which is what the hype after the P4P's announcement was suggesting) then you would get straight vertical lines even if you spun the camera at that speed. Mind you, video cameras with CMOS global shutters are pretty damned expensive -- we're talking $30000 +

Which is why the P4P's use of a mechanical leaf shutter to achieve the same result would've been very impressive indeed at it's price range. But alas -- just hype.
 
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Yes I can see it now. Actually looked a lot better than I thought it would.
 
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Yeah, I didn't quite see how they could do a mechanical shutter for video -- for stills sure, but for video ... I don't think so. A mechanical shutter for a sensor of 1 inch would be fairly large and therefore require a substantial movement at least 30 times a second. A typical DSLR will have a shutter lifetime rating around about 200K actuation's which would last less than 2 hours at 30fps.

The mechanical shutter on DSLR's and Mirrorless cameras are, to the best of my knowledge, only used for stills.


Brian
The P4P has a leaf shutter, not a more traditional plane shutter as used in DSLRs. On the other hand, we should've known better. Compacts like the sony rx100 line also use a leaf shutter, and never made any claims about using it in video.
 
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I don't think any video cameras use a mechanical shutter of any kind, not practical. I have read that very high end stuff (Arri, etc.) use a rotating mirror as a shutter.

But getting back to the P4P, in the ad copy DJI states:

Aerial imaging is not only used to capture landscapes; it brings new perspectives to everything from action scenes to motor racing. Capturing objects moving at high speed has always been a challenge for flying cameras using an electronic shutter. This is why the Phantom 4 Pro is the first DJI Phantom to use a mechanical shutter and a large-aperture prime lens.

A mechanical shutter with a max speed of 1/2000s eliminates rolling shutter distortion which can occur when taking images of fast moving subjects or when flying at high speed. The electronic shutter has also been improved with a max shutter speed of 1/8000 seconds, and a new Burst Mode shoot capable of shooting 14 fps at 20 megapixels to catch the perfect moment.


Where does it claim that a shutter is used for video? I guess they don't explicitly state that it isn't used for video, but as many have pointed out, how could it be?
 
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I don't think any video cameras use a mechanical shutter of any kind, not practical. I have read that very high end stuff (Arri, etc.) use a rotating mirror as a shutter.

But getting back to the P4P, in the ad copy DJI states:

Aerial imaging is not only used to capture landscapes; it brings new perspectives to everything from action scenes to motor racing. Capturing objects moving at high speed has always been a challenge for flying cameras using an electronic shutter. This is why the Phantom 4 Pro is the first DJI Phantom to use a mechanical shutter and a large-aperture prime lens.

A mechanical shutter with a max speed of 1/2000s eliminates rolling shutter distortion which can occur when taking images of fast moving subjects or when flying at high speed. The electronic shutter has also been improved with a max shutter speed of 1/8000 seconds, and a new Burst Mode shoot capable of shooting 14 fps at 20 megapixels to catch the perfect moment.


Where does it claim that a shutter is used for video? I guess they don't explicitly state that it isn't used for video, but as many have pointed out, how could it be?
DJI never stated it (though the language above is pretty ambiguous, to be honest). However, plenty of initial previews on the web did.

E.g., from Cinema5d (a site focused on semi-professional-to-professional video and really ought to know better):

For those of us without the change to put down on a DJI Inspire 2 ($3,000 – $6,000), we have the next best thing: the new DJI Phantom 4 Pro. The camera on the drone comes equipped with a new 1-inch 20-megapixel sensor and roughly 12 stops of dynamic range. It is 4K-capable up to 60fps with a maximum bitrate of 100 mbps in H.265 compression, and it has a mechanical shutter, so no more skewed rolling shutter videos. (DJI Phantom 4 Pro - Impressive Upgrade for Semi-Professional Aerial Films | cinema5D)


The mechanical shutter of the P4P being used in video is a pretty widespread misconception out there.
 

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