Malakai_UK
lvl.4
Flight distance : 536115 ft
United Kingdom
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Just my opinion here, an ND filter wont fix the artifacting you are seeing, it will allow you to set your shutter-speed to the 180 degree rule (double shutter over fps e.g. 25fps shutter at 50, 30fps shutter at 60) This will create the "cinematic" look but for the true "cinematic" feel you need 24fps and a shutter speed at 48 (or 50 if its closest). This will create a small amount of motion blur in your video. This works because of the way the brain processes our dreams and it was found that video shows at 24fps with the 180 degree shutter gave the video a dreamlike feeling.
The issue you are seeing is down to the bitrates that the Mavic captures video footage at and funnily enough, just last night I was looking at the Mavic's video bitrates and doing a little analysis. Taking a short 5 second clip at each resolution and frame-rate I was able to calculate the bits per pixel to try and figure out what is the most optimal resolution to prevent artifacts and capture the cleanest video. Take a look at the data below.
This shows the resolutions, total number of pixels, frame-rates and bitrates. In my basic analysis I calculated the bitrate per frame (bitrate divided by the fps) to give the available bitrate per frame. I then divided this bitrate per frame with the total number of pixels, giving the available bitrate per pixel per frame. I understand that there are compression algorithms that are taking place however these are based on the fact that where there are a lot of pixels changing quickly this is where the bitrate wont be able to keep up during compression. So taking those numbers I produced a chart to show the bitrate per pixel per frame. In a nutshell this shows the available bits per pixel, meaning a longer bar means more data can be captured, meaning less artifacting.
Looking at the chart you can see that 1080p@30fps is the longest bar, this is because 1080p@30fps has a bitrate of 40Mbits/per second, you might say, oh, well, 4k cinematic@30fps has a bitrate of 60Mbits/ps, sure it does, but it also has four times the resolution to compress using that 60Mbits/ps bitrate compared to 1080p. Because of this, 4k video, no matter what resolution are outputting at, the captured footage will still have more artifacting compared to any of the other resolutions.
So my results are that 1080p@30fps will capture the cleanest video footage however it doesn't quite get that cinematic feel using 30fps. 1080p@24fps comes in second and will produce that cinematic feel.
4k, while it looks great and is nice and sharp the bitrate is too low. My personal opinion is that the 4k should be a minimum of 100Mbits/ps but its finding a memory card that can do sustained write at this speed is going to cause issues that DJI wont want to deal with.
Going by the results I would suggest that if you are outputting at 1080p want the cleanest video, use 1080p@30fps and if you want the cinematic feel, go for 1080p@24fps
If you are outputting at 4k use 4k cinematic@24fps
Also remember to use the lowest ISO you possibly can, ideally 100. This will help prevent digital noise, higher ISO's introduce digital noise, this additional noise will the make the compression algorithm have to sacrifice information in some areas of the frame to compensate, the end effect being visual artifacting.
Hope this helps
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