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Slow flicker/dark lines in sunlight
154 24 4 days ago
BumblerBee
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I was flying the other day at sunset, and noticed at one point dark horizontal lines going up and down the frame. One would usually see such lines in artificial lighting when the frame rate does not agree with the power line rate, e.g. 50Hz. However, here I was filing in daylight.

In the attached image I increased the contrast to make them more noticeable, and placed two orange lines at the center of two of the more prominent lines.

Can it have something to do with facing the sun?

I had a DJI ND8 filter on. Camera was in PAL mode, 2.7K 25fps and 1/100 shutter speed.

I also got some Moire effect in the waves, and I don't know if it was because of the filter. I can also se camera ring reflection in the filter, which I should rememebr when flying with ND filters in the futue.

DJI_0039.MP4_snapshot_00.02_[2017.08.12_21.27.34].jpg
4 days ago
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Bekaru Tree
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hi bumbler - even with yr orange lines it is tough to see anything wrong in yr picture.

Lense flare also appears for me when i have filters on - slight light curve in lower half/quater of image - can be eft or right side.
I find this happens when i am flying at about 45 degrees away from the sun (either side) -
when it does appear for me now i simply turn a bit more away from the sun and then it dips out again.
4 days ago
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QuadKid
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Bekaru Tree Posted at 2017-8-12 13:21
hi bumbler - even with yr orange lines it is tough to see anything wrong in yr picture.

Lense flare also appears for me when i have filters on - slight light curve in lower half/quater of image - can be eft or right side.

I agree, looks like a little flare ring, it doesn't travel to the top of the frame so seems to be a light reflection ring.
Your not flying with the Bubble cover on are you?
4 days ago
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Bekaru Tree
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No - i am not flying with bubble cover on - only nd filter.
it is the light from the sun reflecting off the ring around the lense which then reflects onto the inside of the nd filter and back into the appeture.
4 days ago
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Bekaru Tree
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tonight i foubd some interesting information about temperature and radio signal - i am not sure if it applies to mavic but the radio frequency is the same.
In summary it says that the variation of signal strength can best be explained  by the variation in temperature.

I think that drone pilots often fly through pockets of varying temperature air - if the above statement is correct then this might be a possible candidate for causing that problem in yr picture - which i cant see but by yr description is something i have encountered but not found any likely reasons for - until possibly now.? Screenshot (9).png
4 days ago
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Tombolian
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Yes!!! I have it too, I think I know exactly what you are talking about.  For me, it seems to only happen in the hours before sunset, when the sun is low on the horizon and I'm flying at a 90 degree angle to it, I seem to notice it the most.  Let me try to find one of my examples, or maybe I can even create one and try to link to it (what do I use, Dropbox?  Gonna have to figure it out).
4 days ago
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Tombolian
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United States
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Does this work?  If it does, you can see it at approximately 3.5 seconds if you focus on the lower left area of the screen.  Horizontal dark lines that move downward in an interference sort of way.  I'm looking for better examples, but this was just a test to see if I could post one.
4 days ago
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eyecapture
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Canada
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Prop shadow?
4 days ago
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Tombolian
Student Pilot
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United States
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Nope, not prop shadow.  Here is another better example, as is this.
4 days ago
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Tombolian
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OK, well, when I view those, at least from my iPad, you really can't see it very well, way too much compression in the final result.  I'll have to do a screen grab for the perfect example.  Sorry if I'm stomping on this OPer...
4 days ago
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Tombolian
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United States
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ok,
4 days ago
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Tombolian
Student Pilot
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United States
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aargh... here
4 days ago
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dronist
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United States
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It is a prop shadow. This usually happens when you suddenly trun fast and the sunlight will hit the props on an angle. You can try the same but turn slowly!
4 days ago
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DJI Thor
Administrator
Japan
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It is the lens flare, did you fly it the gimbal cover? Please try to fly it without the gimbal cover. And other suggestion is to avoid direct sunlight to the camera.
The influence of the Moire patterning can be relieved by decreasing the sharpness of camera. Go to camera settings and decrease the sharpness. It is recommended to lower the levels of sharpness one by one to observe the effect.
4 days ago
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Tombolian
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Thanks again Thor, I was flying without the gimbal cover, I will try the recommended adjustments to sharpness and report back if I can fix the effect.
And Thank you EyeCapture and Dronist, having now googled 'Prop Shadow', indeed, that's what it is.  Ahh. Smarter every day!
4 days ago
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dancopter
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Yes, simple prop shadow, nothing too serious.
4 days ago
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BumblerBee
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Tombolian Posted at 2017-8-12 16:21
Nope, not prop shadow.  Here  is another better example, as is this.

That's the sun flare inside the camera optics.
I'll try to upload my horizontal flicker problem...
3 days ago
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BumblerBee
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Norway
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Here is a 4 second video sample. Posting from mobile. This is a chached version, but the same effect is no the SD card footage, so this has nothing to do with signal strength.

The flickering effect is most visible in the lower left.

https://drive.google.com/file/d/ ... 2M/view?usp=sharing

@DJI Thor: "The influence of the Moire patterning can be relieved by decreasing the  sharpness of camera. Go to camera settings and decrease the sharpness.  It is recommended to lower the levels of sharpness one by one to observe  the effect."

I am using sharpening +1 to disable the in-camera noise reduction. With sharpening at 0, NR function becomes enabled and removes a lot of shado detail in for example foliage. A suggestion for DJI is to separate sharpness and noise reduction functions into 2 different settings.
3 days ago
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calmari
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BumblerBee Posted at 2017-8-13 01:30
Here is a 4 second video sample. Posting from mobile. This is a chached version, but the same effect is no the SD card footage, so this has nothing to do with signal strength.

The flickering effect is most visible in the lower left.

I see the lines you are talking about.
3 days ago
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Bekaru Tree
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Hi Tombolian - there are 7 lines in yr picture - there are also 7 stepped rings around the camera lense - Coincidence?
You are also flying at about 45 degrees to sun - which are the conditions we keep seeing when reflection issues occur.
I do not think it is prop related - does not look like it and props are always visible in top quater not image throughout per yr example.
3 days ago
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Tombolian
Student Pilot
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United States
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Bekaru Tree Posted at 2017-8-13 05:22
Hi Tombolian - there are 7 lines in yr picture - there are also 7 stepped rings around the camera lense - Coincidence?
You are also flying at about 45 degrees to sun - which are the conditions we keep seeing when reflection issues occur.
I do not think it is prop related - does not look like it and props are always visible in top quater not image throughout per yr example.

Hey Bekaru Tree,
It wasn't obvious to me at first, but it makes sense that the props are simply casting a shadow on the lense, they aren't in the lense themselves, just their shadow, as occurs when the camera is somewhere between 45-90 degrees perpendicular to the sun.
I'm going to set out to replicate this today (tonight).  I'm convinced it's prop shadow unless I can't replicate it.
3 days ago
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Bekaru Tree
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South Africa
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Tombolian Posted at 2017-8-13 09:37
Hey Bekaru Tree,
It wasn't obvious to me at first, but it makes sense that the props are simply casting a shadow on the lense, they aren't in the lense themselves, just their shadow, as occurs when the camera is somewhere between 45-90 degrees perpendicular to the sun.
I'm going to set out to replicate this today (tonight).  I'm convinced it's prop shadow unless I can't replicate it.

cool - i will be interested in the outcome - let us know
3 days ago
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BumblerBee
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Any ideas on my horizontal line flicker (video snippet posted above) - that does not seem to be props-related?
3 days ago
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Tombolian
Student Pilot
Flight distance : 117053
United States
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BumblerBee.  Pay attention.  Those lines are prop shadow.  I just reproduced it.  it's super easy.  See here.  The props are casting a shadow onto the lense.  Simple as that.  Everybody else, stop calling it lense flare.  That is present too, but it's not what causes the dark lines...
3 days ago
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BumblerBee
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Tombolian Posted at 2017-8-13 17:32
BumblerBee.  Pay attention.  Those lines are prop shadow.  I just reproduced it.  it's super easy.  See here.  The props are casting a shadow onto the lense.  Simple as that.  Everybody else, stop calling it lense flare.  That is present too, but it's not what causes the dark lines...

Good catch! Thank you. I thought that reply was pertaining to something else. As you said, "flair" cropped up in the conversation, while I referred to it as flicker...

Interestingly, I was flying with a hood like this one:
http://www.ebay.com/itm/PGY-Lens ... c-Pro-/182628682936
Thought that it would shade for prop shadows, and probably it did, seeing as the lines only appeared in the lower corners and not across the whole of the frame.
In any case, one more thing to pay attention to when flying and framing a shot!
2 days ago
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