Hi

Why is the Mavic Air changin FOV (a lot) when going from 30fps to 60fps?
I could understand why the FOV would change if I changed the resolotion like on the GoPro depending of how much of the CCD you use.
But I can't understand why the FOV changes that much just because I change the fps.

I am only filming in 1080p btw.

I hope for an explanation, and what is the best advantage of the CCD.

BR
Steen

I think it's down to how it uses the pixels on the sensor to handle the change in frame rates. It will use a different type of pixel binning technique for any given frame rate and resolution. The video actually uses all of the sensor to capture video. It just bins pixels to bring the resolution down. This is why at higher frame rates you get bad aliasing and jaggies because it bins more pixels to sustain the higher fps.

Malakai_UK Posted at 2018-4-4 13:11
I think it's down to how it uses the pixels on the sensor to handle the change in frame rates. It will use a different type of pixel binning technique for any given frame rate and resolution. The video actually uses all of the sensor to capture video. It just bins pixels to bring the resolution down. This is why at higher frame rates you get bad aliasing and jaggies because it bins more pixels to sustain the higher fps.

Good info to know.   

Malakai_UK Posted at 2018-4-4 13:11
I think it's down to how it uses the pixels on the sensor to handle the change in frame rates. It will use a different type of pixel binning technique for any given frame rate and resolution. The video actually uses all of the sensor to capture video. It just bins pixels to bring the resolution down. This is why at higher frame rates you get bad aliasing and jaggies because it bins more pixels to sustain the higher fps.

I doubt if that is the reason the FOV changes (is reduced) when you the framerate.
The framerate should not have anything to do with FOV. The only thing that does is increasing the amount of information that needs to be processed. It won't change the pixel binning, when the resolution you use is still the same. .

So if the FOV really changes (I can't confirm that) when you move up to 60fps the only reason I can think of is that the bitrate gets too high.
But that won't make sense as the Air can do 4K 30fps, which is twice the size of FHD 60fps.
I am really puzzled.

Montfrooij Posted at 2018-4-4 22:02
I doubt if that is the reason the FOV changes (is reduced) when you the framerate.
The framerate should not have anything to do with FOV. The only thing that does is increasing the amount of information that needs to be processed. It won't change the pixel binning, when the resolution you use is still the same. .

It's not a change of FOV the OP is experiencing. The image you see will look like its zooming in or out slightly due to the differences in the pixel binning process. its similar to digital zoom.
As a basic example for pixel binning.
The whole sensor is used to capture the video frame but due to the size of each frame there is way too much information for the processor to cope with, so a process called pixel binning is used to reduce the amount of data being sent. Imagine if you had a grid of 10x10 pixels (100 pixels) and your processor can only handle 20 pixels 30 times a second. You still need to capture enough information so see the square but not so much that the processor is overloaded. So to do this you only read every fifth pixel, skipping or binning the ones in between. Now you have your 20 pixel square and this can be processed at 30 times a second. That's ok. Now you bump the frame rate up to 60fps. The processor can process a 10 pixels 60 times a second and to do this will need to read every tenth pixel in grid. Binning the rest. Now when you play this video back it may have slightly more jagged edges or create moire in some areas. Due to the number of pixels it has had to bin from the original image. The other effect it may have is a change in the size of the image captured by a few pixels. Giving the appearance of being zoomed in or a perceived change in FOV.

Hope this makes sense.

Malakai_UK Posted at 2018-4-5 09:02
It's not a change of FOV the OP is experiencing. The image you see will look like its zooming in or out slightly due to the differences in the pixel binning process. its similar to digital zoom.
As a basic example for pixel binning.
The whole sensor is used to capture the video frame but due to the size of each frame there is way too much information for the processor to cope with, so a process called pixel binning is used to reduce the amount of data being sent. Imagine if you had a grid of 10x10 pixels (100 pixels) and your processor can only handle 20 pixels 30 times a second. You still need to capture enough information so see the square but not so much that the processor is overloaded. So to do this you only read every fifth pixel, skipping or binning the ones in between. Now you have your 20 pixel square and this can be processed at 30 times a second. That's ok. Now you bump the frame rate up to 60fps. The processor can process a 10 pixels 60 times a second and to do this will need to read every tenth pixel in grid. Binning the rest. Now when you play this video back it may have slightly more jagged edges or create moire in some areas. Due to the number of pixels it has had to bin from the original image. The other effect it may have is a change in the size of the image captured by a few pixels. Giving the appearance of being zoomed in or a perceived change in FOV.

That does make sense, although I would not call that 'a lot' as the OP was experiencing.
But he (or she) did not provide an example, so I'm not sure what 'a lot' means

Thanks for a good explanation. Now when you say it, I can see difference in the quality. I didn't notice that before.

I have just made a little video, showing the difference



BR
Steen

Montfrooij Posted at 2018-4-5 09:51
That does make sense, although I would not call that 'a lot' as the OP was experiencing.
But he (or she) did not provide an example, so I'm not sure what 'a lot' means

I have posted a video now in the thread so you can see what i mean :-)

SteenPedersen Posted at 2018-4-5 11:17
Thanks for a good explanation. Now when you say it, I can see difference in the quality. I didn't notice that before.

I have just made a little video, showing the difference

Wow, that actually is a lot.
And I have not seen that on other camera's before (not that I have a lot of them   )

I agree, that is significant and interesting to know.

The most interesting thing is, that it zooms out again with 120fps. This doesnt make any sense...

Does anybody has news in this strange behavior?