Actually, that's a very good question and one I'm more than happy to answer. It could be beneficial to a lot of people new to video. I'll try to keep it basic and not get into the nitty gritty because there is a lot to consider.
First off, I base it off of 27 years experience. I've worked in television since 1993. That's my background. ? Newb to drones, but video is my thing.
There are two important considerations. Bitrate and framerate. I'm not sure how the
MA2 handles this in different recording situations, but I'll be testing it out the moment I've got a full charge on the battery to see exactly what each recording mode gives. But for today, without that info available to me, I'm going to assume that the UAV records at 120 megabits per second in both 60fps and 30 fps. 120 megabits of information are recorded each second. Not each frame. That means at 60fps, each frame only has an average of 2 megabits of information. At 30fps, that average goes up to 4 megabits of information per frame. Note I didn't say each frame HAS only 2 or 4 megabits of information, because it doesn't work that way. Its an average. That's where the codec comes in and calculates what information from one frame can be carried over to the next one (and further along) to save on space. That's as basic as I can make how bitrates and frame rates work together along with the compressor/decompressor. Keep in mind that the container file (MOV or MP4 in this case) has zero bearing on any of this. Its simply a container for the data, which is the codec (H.265 or H.264).
In 4K, H.265 is considerable more efficient at making a better picture from lower bitrates compared to H.264.) You can google exactly how much and why if you're curious, I'm just trying to keep it basic here, like I said. So if the
MA2 gives you the option to record 4K30 using H.265 or H.264, I would always pick H.265 because of the better compression algorithm which will result in a better picture to the eye. Its a smart move that DJI only allows H.265 at 4K60 because even at 120 megabits a second, H.264 would start falling apart a bit.
Essentially the bitrate is the amount of information (a cup full of water) and the frame rate is how often that information is taken. (How often do you drink from that cup.) The faster you drink from it, the faster it will be empty. But if you have a larger bitrate (larger cup), it will take longer to empty at a faster frame rate.
*Unless* 30fps is limited to a lower bitrate than 60fps at the appropriate ratio for the H.265 codec that would result in things being equal. I don't have the
MA2 yet, so I can't do a side by side comparison or get the exact numbers for the bitrates.
This of course also doesn't take account variable bitrate... I'm assuming it's CBR (constant bitrate). It may very well be VBR. In which case, things get even more complex and interesting.
Even with VBR, the answer is essentially the same, but if there's less motion, the bitrate goes down and if there's more motion it goes up to the theoretical max allowed. Either way, the more information you have per frame, the crisper it will be.
Ever wonder why your slow motion videos look janky compared to 30, 24 or 60 fps even though it says it's 120 megabits a second? There's less info to go around in those 240 frames a second.
So if you're color grading using an 8-bit codec, you want as much data per frame available and as such, want as high of a bitrate as possible. If you record a slower fps and can maintain that bitrate, you will have more information to process those grading choices.
Anyway, I did my best to keep it basic and explain it in laymen terms. Hopefully it helps you out a bit to understand why filming in 60fps result in lower quality video compared to 30.