I’ll preface this by saying my experience with the Mavic is quite limited so far, because I have actually had a unit in my possession for only a very short period of time, since I’ve had to send it back to DJI for replacement twice now. That said, here are my thoughts on this whole video image quality thing. I believe it can all be chalked up to two things really: (1) A very noisy sensor, even at lowest ISO, and (2) poor compression / processing algorithms used by DJI. Let me explain.
When I first got my Mavic, I did what most people were recommending online and set the picture style to Art / D-Cinelike and sharpness, contrast and saturation all at -1. After doing this, I also had an issue with the watercolour video phenomenon. It looked like the image was out of focus, but I was religiously tapping to focus, and some parts of some scenes had more detail than other parts. This led me to believe it was a compression or noise reduction problem rather than a focus problem.
So started messing around with the settings, and found that if I moved the sharpness back to 0 or +1, much more detail was present again. But also, even at -1, when I increased exposure, detail reappeared in some cases. I even have one example of footage where some weakly lit trees start off as watercolours, and as I increase the exposure, detail reappears in the trees, in increments exactly corresponding to the clicks on the scroll wheel.
I haven’t yet a chance to do a proper set of tests, but here’s my theory, based on my limited experience and observations so far. The watercolour effect occurs when there’s a certain interaction between exposure and sharpness setting, as dictated by the algorithm DJI uses. As you decrease sharpness, the exposure threshold at which the watercolour effect appears is lowered. For example, if you have some trees that show normal levels of detail with sharpness at 0 and exposure at 0 EV, if you lower the exposure to -1 EV, not only does the scene get darker (of course), but the detail vanishes and is replaced by the watercolour effect. Conversely, if you increase sharpness to +1 and keep EV at -1 in the example above, while the scene remains darker, the detail in the trees comes back. In other words, instead of just applying a sharpness mask to the video (as is done with most other cameras I’ve used that have a sharpness setting), sharpness on the Mavic controls the threshold at which noise reduction is applied.
I think DJI is taking this approach to limit the heavy noise produced by this sensor (it is afterall a tiny sensor). The problem is, it’s not a well implemented approach, as the noise reduction that’s applied is WAY too heavy handed. BTW, if you don’t believe me about the heavy noise this sensor produces, try turning up the sharpness to +1 or +2… the video becomes extremely noisy (even with well-lit scenes). And not in the way you’d expect from a sharpness mask being applied… it’s more like the inherent noise of the sensor is no longer being hidden by noise reduction.
So in order to fix this, I think all DJI needs to do is alter their sharpness and / or noise reduction algorithms... because right now, they kind of suck.
Now, what have I been doing to get around this issue for now (with the footage I managed to take during the brief period where I actually had a Mavic)? Basically, I turn the sharpness UP to 0 or +1. This results in footage that is very noisy. BUT, I then deal with this noise in post-processing, using an awesome noise reduction plug-in called Neat Video. It is most definitely a huge pain in the butt though… not only do you need to spend time tweaking the noise reduction settings, but rendering takes MUCH, MUCH longer, especially on 2.7k or 4k footage (I’m talking an order of magnitude longer). But it’s the only way I’ve found for now to get usable footage from the Mavic.
Another issue I’ve noticed that sort of relates to this and was brought up in an earlier post on this thread is the weird pulsing that I’ve seen in most of the videos I’ve taken with the Mavic so far (it’s especially obvious in darker areas, but also sometimes in brighter areas). After doing a fair bit of research, I learned that this is the result of the compression algorithm used by DJI, which appears to reset the compression keyframe every 8 frames. I’m not exactly sure what that means, but basically there is a drastic change in the image every 8th frame (you can see this by moving through the footage frame by frame). The end result is the pulsing effect that’s observed. Essentially, again, DJI’s compression algorithm sucks.
I’ve learned of a way to deal with this as well, which is to use a plug-in called Flicker Free. It works quite well (substantially reduces the pulsing, even if it sometimes doesn’t completely eliminate it), but again, it takes extra time to refine the settings, and the render times go up substantially again. Using both this and Neat Video, my render times can be about 40 times what they are without these plug-ins!!! Also, the combined cost of these plug-ins is about US$225… a significant chunk of change. And Neat Video doesn’t work well with Davinci Resolve, so really you need either Adobe Premiere or Final Cut to use it, which themselves cost a lot of money.
Obviously, I hope DJI gets their act together on this very soon. I haven’t had a Mavic to use for 2 months now, so maybe they’ve even done it already.
