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Pocket 2 exposure flicker
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2529 55 1-16 11:11
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MKosmo
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I first noticed an exposure flicker when filming inside, but i put this down to the lighting frequency.

However i have noticed that in certain scenes even outside an observable 'blip' in the exposure, almost like a blink of an eye.  If the scene has lots of movement , you dont notice it.

A scene thats fairly still and has areas of the same colour ( like grass ) tends to highlight it.

At 60 fps, it happens every 1s ( for one frame ).  Also seems to happen in all resolutions. However frame rate vary's the frequency.


When editing the clip, it can be seen in the RGB video scopes the exposure does twitch at these 1s intervals.

No i dont know if its unique to my camera, or its on all of them.  Anyone noticed this effect ?   

I have put a youtube clip below, but unfortunatly watching it back - the youtube compression almost removes the issue, however you can still see the RGB scope twitching !


1-16 11:11
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Montfrooij
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By accident rendering in another framerate?
1-18 00:46
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MKosmo
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Montfrooij Posted at 1-18 00:46
By accident rendering in another framerate?

Hi and thanks for suggestion. For this problem, you can see the effect in viewing the footage clip straight out of the camera, so no editing or different frame rates involved at this point.   

I've done some more trials and believe this problem only happens in 4K, 50 and 60 fps. I would be very surprised if this issue is not present on all OP2.

Below is a raw clip straight out of the camera.
(possibly the most dull 12s clip ever.... )

https://www.dropbox.com/s/15ntlv67lob39cz/DJI_0047.MP4?dl=0

*make sure you download the clip and view, otherwise you are viewing through a browser window and this is compressed
1-18 03:05
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Montfrooij
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MKosmo Posted at 1-18 03:05
Hi and thanks for suggestion. For this problem, you can see the effect in viewing the footage clip straight out of the camera, so no editing or different frame rates involved at this point.   

I've done some more trials and believe this problem only happens in 4K, 50 and 60 fps. I would be very surprised if this issue is not present on all OP2.

Downloading as we speak!
1-18 04:41
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Montfrooij
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MKosmo Posted at 1-18 03:05
Hi and thanks for suggestion. For this problem, you can see the effect in viewing the footage clip straight out of the camera, so no editing or different frame rates involved at this point.   

I've done some more trials and believe this problem only happens in 4K, 50 and 60 fps. I would be very surprised if this issue is not present on all OP2.

Very strange.
Every second you see a small 'blink' in the footage.
Never saw this before.
(I don't have a P2, so I can't check myself)
1-18 05:51
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MKosmo
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Montfrooij Posted at 1-18 05:51
Very strange.
Every second you see a small 'blink' in the footage.
Never saw this before.

Hi, yes the small blink is exactly the problem !   But thanks for the thought of checking.


Maybe there is a fault with my camera ?

Do no other OP2 owners notice this problem ?  ( 4K 50, 60fps)

Thanks.
1-19 09:25
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Montfrooij
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MKosmo Posted at 1-19 09:25
Hi, yes the small blink is exactly the problem !   But thanks for the thought of checking.

Always good to have a second pair of eyes to rule out certain reasons!
1-19 12:45
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MKosmo
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After returning my OP2 to Amazon, I swiftly received my replacement.

Disappointingly the 4K image problem is still there.  I have had a friend check the raw image file on a completely different computer system and his observation was its like the image changes its focus every second creating the blink.

Looking further into the issue, it happens in all frame rates in 4K.   At 60 fps it happens every second, at 24fps it happens quicker - probably every half a second.



It is most noticeable in D-cine, 60fps and filming a static scene with lots of the same colour / pattern.

Filming a scene with lots of movement your eye won't notice it, but the video editing scopes show it is still there.  As mentioned my YouTube video didn't show the effect so well due to the compression.

As it stands to me, the OP2 is not a 4K camera.   Any filming I do will be 2.7K where the effect can not be seen. - however not really a good workaround !

Both my OP2 cameras have a date stamp 2020/9 - so maybe it is a batch issue ?
1-28 07:47
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DJI-ytao
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I MKosmo, I looked into this issue and what you come across does happen on pocket2.
I shall explain the details:

1.The brightness blink u you post can be observed by oscilloscope. However this blink will be no larger than 0.7/256 (I will talk about this number later) and it is beyond the scope of human eyesight.
2.explain where is the blink from:
video frame is encoded by a certain algorithms. The video generated by pocket2 begins with I frame and then follows several P frames.
(reference: https://en.wikipedia.org/wiki/Video_compression_picture_types)
For a fixed video bitrate, I frame takes more data info and P frame takes less, which causes the image difference between I and P frame , say the brightness.
For complicated scenes, the brightness of I frame will be slightly different from P frame, which causes the blink u observed.

It is OK make video bitrate very big to handle the case (For low resolution& fps, it hardly can be seen ) , the trade-off is made between the file size (bitrate) and the image quality (in this case: brightness difference).
we tests the brightness blink will be no larger than 0.7/256 under sufficient calculations and tests, which is not noticeable via human eye from watching the video.

4k60 is the most video bitrate consuming mode and it is why u may observe it via oscilloscope when the video is about some complicate scenes, e.x. flooded with grass/ plants.

This usually happens at any kind of bitrate sensitive camera, especially for the portable camera ISP. Each camera may have its standard. it is not noticeable bacause the difference is controlled to be beyond human eyesight.
hopes this might help.
2-1 07:56
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MKosmo
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DJI-ytao Posted at 2-1 07:56
I MKosmo, I looked into this issue and what you come across does happen on pocket2.
I shall explain the details:

DJI-ytao thank you for your reply and I appreciate you looking into this matter.

The I and P frame compression do make sense, since in fact when you step through frame by frame - you can see the 'blink' frame is a slightly different image.  So rather than an exposure shift on its own its a product of this different image frame.

I agree in some footage you will not notice this 'blink' with the human eye, even though it is observable on the oscilloscope.

I am not worried about this scenario - but I would disagree with it not being noticeable by the human eye in other scenes.

I was never looking at the scopes in the first instance, what caught my eye - was the distracting visible 'blink' I could see when reviewing footage.

What I find curious - is the same bit rate and scenario - the issue is not observable on the OP1 ?

Is there a different encoding on the OP1, or is this hopefully an issue on the OP2 that may be improved in a future firmware update ?

Thanks.
2-2 15:14
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Blellow
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Did you check anti flicker?  My anti flicker was locked and defaulted at 50.  I use auto assuming it chooses 60 which is the right amount for my country.  I've studied it and I have no flicker from the pocket 2 in 4k 60 and 24 frame rate.
2-3 10:37
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DJI-ytao
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MKosmo Posted at 2-2 15:14
DJI-ytao thank you for your reply and I appreciate you looking into this matter.

The I and P frame compression do make sense, since in fact when you step through frame by frame - you can see the 'blink' frame is a slightly different image.  So rather than an exposure shift on its own its a product of this different image frame.

We will collect more feedback about this case and consider whether to do the modification.
2-3 22:20
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MKosmo
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Blellow Posted at 2-3 10:37
Did you check anti flicker?  My anti flicker was locked and defaulted at 50.  I use auto assuming it chooses 60 which is the right amount for my country.  I've studied it and I have no flicker from the pocket 2 in 4k 60 and 24 frame rate.

Hi, thanks for suggestion.  yes I did try 50, 60Hz and Auto - unfortunately same problem.
2-6 07:58
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MKosmo
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DJI-ytao Posted at 2-3 22:20
We will collect more feedback about this case and consider whether to do the modification.

Ok, thank you.
2-6 07:59
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Dalibor.bosnjakovic
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I have the same problem and frankly it is unacceptable.

@DJI-ytao:  I rally don't see how this explanation that was composed to be so technical can help my image? Should I paste that under my videos and ask my viewers to disregard the flickering that is so annoying. By the way it so noticeable to human eye that I googled it and than landed here on this post. It is so visible and annoying. You should have fixed it already and not wait to collect more data just to decided if your are going to fix it.

I am just going to return my pocket 2.
2-19 07:34
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MKosmo
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Dalibor.bosnjakovic Posted at 2-19 07:34
I have the same problem and frankly it is unacceptable.

@DJI-ytao:  I rally don't see how this explanation that was composed to be so technical can help my image? Should I paste that under my videos and ask my viewers to disregard the flickering that is so annoying. By the way it so noticeable to human eye that I googled it and than landed here on this post. It is so visible and annoying. You should have fixed it already and not wait to collect more data just to decided if your are going to fix it.

Dalibor I agree it is an unacceptable problem, and also like you I am now considering just to return the OP2 - not sure its an issue I want to put up with.

My concern is the possibility its a hardware issue and no firmware will ever fix it.

I would be interested for other people reading this post why they are not commenting ?   Do you not see the problem in your OP2 ? or maybe you feel its insignificant ? or maybe you dont shoot in 4K ? or perhaps the image content type doesn't show up the problem ?
2-20 02:43
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Karl53
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Here the same problem !
2-20 02:55
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Blellow
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I either don't see the problem on my op2 or I don't have it.
2-20 06:52
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MKosmo
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Blellow Posted at 2-20 06:52
I either don't see the problem on my op2 or I don't have it.

Blellow thanks for feedback,  could I ask what manufacture date of your OP2 ?  The ones I have tried were both 9 /2021.   Also which editing software do you use ?   Thanks !
2-20 08:54
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chririva
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Same problem here.
Did this camera really passed your quality tests, DJI?
This camera has no sense
2-23 00:51
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chririva
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Have you tried to zoom into details when flicker occurs?
2-23 12:25
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MKosmo
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chririva Posted at 2-23 12:25
Have you tried to zoom into details when flicker occurs?
[view_image][view_image]

If I zoom into the video I have taken, I can see the level of detail changes noticeably on the flicker 'frame', which does reflect a compression issue.

I notice on your images, the central post in that tower thing is not visible on both, I presume that is your  flicker frame ?
2-23 14:27
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RobCass
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I have the issue as well.
Out of camera files that are unedited and it showed the:

I m not sure if this is because there is so much snow *(2/3) of the screen since it seems to be less when there is more contrast in the shot.
2-23 16:53
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CemAygun
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RobCass Posted at 2-23 16:53
I have the issue as well.
Out of camera files that are unedited and it showed the:Flicker original file - unedited

The flicker on this one is insane, totally unacceptable. But I noticed that it sometimes disappears. Can someone please test with full manual settings to rule out "exposure hunting"? Osmo action had some big auto exposure jumps up until the latest firmware, although it did not oscillate back and forth. It just had some silly, sudden exposure changes under seemingly unchallenging conditions; which a lot of people did not even notice or complain about at all. This is totally something else...
2-23 20:49
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RobCass
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CemAygun Posted at 2-23 20:49
The flicker on this one is insane, totally unacceptable. But I noticed that it sometimes disappears. Can someone please test with full manual settings to rule out "exposure hunting"? Osmo action had some big auto exposure jumps up until the latest firmware, although it did not oscillate back and forth. It just had some silly, sudden exposure changes under seemingly unchallenging conditions; which a lot of people did not even notice or complain about at all. This is totally something else...

I will try today to do a 2 minute video with snow. I also want to test if the snow is throwing it off so I will test 10! 25, 50! 75 snow covering the frame.

Thanks
2-24 05:06
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MKosmo
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CemAygun Posted at 2-23 20:49
The flicker on this one is insane, totally unacceptable. But I noticed that it sometimes disappears. Can someone please test with full manual settings to rule out "exposure hunting"? Osmo action had some big auto exposure jumps up until the latest firmware, although it did not oscillate back and forth. It just had some silly, sudden exposure changes under seemingly unchallenging conditions; which a lot of people did not even notice or complain about at all. This is totally something else...

Yes, have tested with manual setting, with / without nd filters , d cine / normal colour, 50/60hz always there in 4K.

I dont believe its exposure ramping up and down, because going through by frame - you can see the detail changing and not the exposure, its the large change of detail that causes the apparent exposure shift - but only in certain parts of the image. An exposure shift would be the whole image.

Interestingly a few video's like the snow one above, are really bad and obvious - whereas I see it less so in my footage ( but haven't filmed in snow )  However there is a wonderland video filmed in snow in this forum, and even though its YouTube compressed it doesn't look like its present.

2-24 12:42
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RobCass
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RobCass Posted at 2-23 16:53
I have the issue as well.
Out of camera files that are unedited and it showed the:Flicker original file - unedited

I tried different scenarios, but cannot replicate what I had happen the other day.All these files were directly upload to YouTube from the camera card. NO PP.

Test #1:  4K 60 fps, Pro mode, Auto exposure, Auto ISO, no lens filters.
This is exactly how my Pocket 2 was setup when I saw the major flickering a few days ago.

Test #2:  4K 60 fps, Pro mode, Manual exposure, Manual ISO, no lens filters


Test #3: 4K 60 fps, Pro Mode, Manual exposure, Auto ISO , no lens filters


Test #4: 4K 30 fps, Pro mode, Auto exposure, Auto ISO, no lens filters


When I originall saw the issue, I was filming this next to the Sony ZV-1 and a6400 at the same time for a comparision video...possible electronic interference?



2-24 16:44
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MKosmo
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I'm not going to keep pursuing this issue, but I will just leave this clip I found.  It actually shows how good the OP2 can be with regards to detail and nice colours - but it also highlights better than my video the flickering that you can see at points throughout the video.

The very beautiful colourful Madeira,



Note - especially after the first few seconds the green grass scene.
2-25 10:17
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djiuser_RFjLKvah92qe
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I've seen the same effect more inside than outside, however, two things for me reduced flickering, first the upgrade of SD card from Extreme to Extreme Pro, and secondly removing wide angle lens. So it seems that there are more than one factor affecting flickering, and I just ordered a spare lens to see if something wrong with the one I have (all tests I've done on 4k/60 as that is where I've seen it the most).
2-25 11:51
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CemAygun
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Thanks for all the info and tests. So it is not exposure hunting.  The DJI cameras I own (Pocket 1, Action and The Mavic Air) have warnings about card speeds and they stop recording if the card speed is slow for some reason. Maybe pocket 2 tries to adapt instead, by  lowering the bitrate too much. This theory also fits DJI-ytao's explanation. Basically the I frames are full picture, original image frames, where as P (and B) frames are "Delta" frames derived from those I frames. An unsuccessful compression can produce a perceivable quality difference between a fully stored and derived frames.  Depending on GOP length, this might come across as visible flicker.

Well, hopefully it will be fixed soon...
2-25 17:39
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chririva
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Can somebody wake up dji?
They f---- up the video of my trip with this flickering. I will post my video soon.
Next month I may be back in my home country, I will finally send this camera back to amazon. And bye bye, not my business anymore
2-27 02:33
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MKosmo
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djiuser_RFjLKvah92qe Posted at 2-25 11:51
I've seen the same effect more inside than outside, however, two things for me reduced flickering, first the upgrade of SD card from Extreme to Extreme Pro, and secondly removing wide angle lens. So it seems that there are more than one factor affecting flickering, and I just ordered a spare lens to see if something wrong with the one I have (all tests I've done on 4k/60 as that is where I've seen it the most).

Hi,

I think its maybe a red herring to look at flicker inside due to the mains lighting flicker that a camera will capture.  Its a fairer comparison to use outside footage.

Interesting you found the pro card better. I presume that it didn't get rid of it though from your comment ?
2-27 03:46
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MKosmo
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CemAygun Posted at 2-25 17:39
Thanks for all the info and tests. So it is not exposure hunting.  The DJI cameras I own (Pocket 1, Action and The Mavic Air) have warnings about card speeds and they stop recording if the card speed is slow for some reason. Maybe pocket 2 tries to adapt instead, by  lowering the bitrate too much. This theory also fits DJI-ytao's explanation. Basically the I frames are full picture, original image frames, where as P (and B) frames are "Delta" frames derived from those I frames. An unsuccessful compression can produce a perceivable quality difference between a fully stored and derived frames.  Depending on GOP length, this might come across as visible flicker.

Well, hopefully it will be fixed soon...

Its interesting about the speeds, as the other poster mentioned above.

However if OP1 has the same bit rate as the OP2, that would tend to exclude this as a reason if this flicker was never seen on the OP1 , but has been seen o the OP2 ?

Just to be sure though, I am doing a card scan - and I can see all of mine are V30 U1-U3, A1,A2 speeds . So will do a test with the absolute fastest card.

On the DJI specs one of their recommended cards is the Samsung EVO PLUS 32GB, U1.   I have the exact card and the problem exists on this one, however this is one of the slower cards ( but still within the Mb/s requirement )
2-27 03:52
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Ranjan
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To the Original post
Was this clip shot on battery saving mode which uses lower bit rate or high quality which uses higher bit rate in 4k 60p?
2-27 05:02
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MKosmo
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Ranjan Posted at 2-27 05:02
To the Original post
Was this clip shot on battery saving mode which uses lower bit rate or high quality which uses higher bit rate in 4k 60p?

Hi, alway used 'BATTERY SAVER' mode in the quality setting.   Since anything above 30fps you dont have the choice.

I seem to remember there was a thread about the quality mode, and I'm not sure the bit rate changed and the consensus was better to leave it in battery saver mode regardless.
2-27 06:41
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Blellow
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It may be a unique combination of factors involving steadyshot and exposure settings reaching a flickering threshold.  
2-27 07:56
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Ranjan
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MKosmo Posted at 2-27 06:41
Hi, alway used 'BATTERY SAVER' mode in the quality setting.   Since anything above 30fps you dont have the choice.

I seem to remember there was a thread about the quality mode, and I'm not sure the bit rate changed and the consensus was better to leave it in battery saver mode regardless.

He talked about low light video 4k 30p gives better results when shot in high quality. There is no such issues in his footage which is available in video description to download.
Try this test hope your flicker problem is gone.
2-27 08:33
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MKosmo
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Ranjan Posted at 2-27 08:33
https://www.youtube.com/watch?v=PNW1bmQD0k8
He talked about low light video 4k 30p gives better results when shot in high quality. There is no such issues in his footage which is available in video description to download.
Try this test hope your flicker problem is gone.

Hi Ranjan,   Thank you for the suggestion.

I have now tried 4K 30fps, HIGH quality mode - the problem is still there. It is not as noticeable as 60fps due to the different frequency bit it is is still present at 30fps, HIGH QUALITY mode and BATTERY saver mode.

I dont use my OP for low light footage , and I can imagine shooting low light is a different technical scenario - hence why you don't see the effect in the footage for the video attached above.

2-27 09:23
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MKosmo
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Blellow Posted at 2-27 07:56
It may be a unique combination of factors involving steadyshot and exposure settings reaching a flickering threshold.

Hi, I believe trying the camera in manual mode would take out the effect of reaching a limit close to a threshold.   With it being mechanically gimbal stabilised there should be no steady shot artefacts such as might be present in a  digitally stabilised image.
2-27 09:26
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chririva
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Here my video taken in mountain, affected with flickering issue. You can see it in the beginning of the video


3-4 06:15
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