poliakov
 lvl.2
Flight distance : 94639 ft
United States
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Hello,
Much has been written about the Mavic Blurry Edge / Uneven Focus issue. My unit appears to be affected. I wanted to collect more information and hopefully get more clarity on this from DJI and or others who might be more familiar with the problem.
By way of background,
There was a good thread here: http://forum.dji.com/thread-69767-1-1.html
A good whole blog here: https://www.capedigital.com/journal/my-mavic-has-a-lens-issue
And more here: http://mavicpilots.com/threads/h ... d-uneven-focus.717/
Symptoms
Most of those affected report a "blurry edge" or a "washed out" portion of the image - sometimes on the left, sometimes on the right. A few have figured out that if you tap on the blurry area, it will come into focus but at the expense of another area becoming blurry. Unlike the "blurry background" effect that is natural when taking a closeup (and sometimes desired), this issue involves blur affecting objects that are roughly the same distance away from the camera. Some have described it as a "tilt-and-shift" effect. In clinical parlance, it's as if the Mavic has somewhat of an astigmatism.
What causes it?
Alas, I haven't seen a "real" explanation from DJI staff as to the root cause of the issue. It would be really nice to know! Absent any official explanation, some have proposed that, perhaps it's a manufacturing defect in the camera. The lens is, possibly, installed at a slight angle relative to the sensor; not perfectly parallel. This is explained well in this thread, around Page 3: http://forum.dji.com/thread-69767-1-1.html That explanation makes the most sense to me. However, perhaps others have similar symptoms for other reasons too.
I've done a few "tests" if you will which seem to confirm the hypothesis. My results are below.
The "Table Test"
Place unit on edge of table, camera looking down over the edge. Keep drone completely stationary. Aim camera straight down at (old) hardwood floor. Set camera mode to RAW. Tap to focus in the upper-left corner. Take a picture. Press "center focus" button and take another picture. Don't drop drone. Tap to focus in the lower-right corner. Take another picture.
All three images look roughly like this:
But zooming in on the top-left and bottom-right corners we notice stark differences in focus:
All of my RAW DNGs are on DropBox here:
https://www.dropbox.com/sh/8kjwfv5hybv6wyj/AADFhVp6loODMrfWVrVL-G0Na?dl=0
What this means is, just as we suspected, the camera is incapable of keeping the whole frame in focus. Thus every time you take a picture, something is bound to be blurry. Good news is, we have at least some control over where the focus will be. Another important point to make here is that the drone is kept completely stationary during this test. Thus we can say with relatively high confidence that the problem isn't caused by gimbal vibration, propeller vibration, compass and so on. One thing I haven't done is calibrate the IMU. I'll be extremely surprised if that fixes the issue! But will try soon.
The " ark Test"
Same idea but now we are hovering with some altitude above ground, looking well-textured objects below. Also shoot 3 pictures, focusing on top-left, center, and bottom-right:
And we get similar results:
Again, all the original DNGs are here:
https://www.dropbox.com/sh/8kjwfv5hybv6wyj/AADFhVp6loODMrfWVrVL-G0Na?dl=0
The alarming bit is, now in the "focus on center", the right side appears much more blurry than the left! It looks like the blur is now less centered, more biased towards the right. Does this have to do with being a further distance away from the subject? I'll admit its only an initial impression. Perhaps someone can with more imaging experience can look at my DNGs and have more to say.
Many Questions
I'll say it again - DJI - it would be really nice to get a technical statement from you as to what the cause of the problem is. Going with our assumptions, the next natural question is - can the blur be centered symmetrically?
That is, by tapping on a certain sweet spot (between center and bottom right?) or by playing with manual focus, can we get an image where the edges appear blurry to about an even degree on each side. That would probably be most visually appealing and perhaps even livable. I haven't managed to achieve that with stills, but only tried a couple of times. With video, I got mixed results. Of course, video frames are much more problematic, prone to blur from vibration, compression and so on. I tried a few things and here are some video frames:
Of course, very often when flying a drone, blur on the top (where the sky is) may not even be apparent.
Next question - if the blur indeed can be "centered", then can this issue be addressed with software? That would be nice... I can't tell...
So what do we do?..
I've read a few stories of people complaining to DJI, sending their Mavics back, waiting 10 days or more, and then receiving a different unit that's also blurry! That is a bummer . DJI folks, your silence on this isn't really helpful. Most of all right now I'd appreciate more information:
1. If I send my drone back, how do I know I won't be one of those unlucky customers that receives another blurry drone?
2. You guys must've seen this many times and you must know what the problem is. Can you tell us definitively?
3. Maybe you're working on a way to fix it in software? Is that possible? Can you tell us that?
As far as other customers - anyone manage to solve this manually? Any advice for me? For what it's worth, thanks a lot for reading. Cheers!
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