Color breathing

[RaptorMan]

I shoot in manual and mostly with a 4-stop ND filter unless it's closer to sunrise or sunset where I'll use a lower ND filter or just a UV filter when it's dark. Originally I was shooting at 24fps but I prefer the smoother feel of 30fps so that's what I use now. I always shoot in 4K as I can downres to HD in PP.

The one artifact I still get is a kind of breathing color change that can change about every second or so but tend to change when the lighting conditions change. I'm thinking this is due to auto white balance and for my next tests I plan to lock it in manual but would appreciate any ideas on how best to do this. My background with photography and shooting in RAW means there isn't much need to worry about white balance as that's all going to change when you go to PS so I just don't worry about it with stills. Video, however, looks to be a different beast and seems to require a locked WB.


Brian

 

[InterMurph]

It's almost certainly auto WB that is changing the color on you. I can't think of what else it might be.

 

[Harryscopic]

Yes, whether you correct the color or not, I find it generally best to record it constant. Besides, correcting variable colour in post can be tedious.

 

[RaptorMan]

Yeah, I guess I should have done this earlier but my workflow with stills didn't require using anything other than AWB. Lessen learned I hope.

So, perhaps this week or next I'll make a trip to test the locked down WB. Sadly I need to travel in order to do any flying.


Brian

 

[Quadpilot]

One way to get consistent color is to use manual WB and take a short exposure of a color chart like a Passport prior to launch. Makes color balancing between clips where the light has changed much easier. This is assuming you haven't changed color mode, obviously.

 

[RaptorMan]

Normally you use a grey card to manually adjust WB, but for stills photography I just shoot AWB and adjust as needed in PS/Lightroom.

For me the bigger problem is the WB pulsing/breathing very quickly on a second by second basis that makes for a very obvious effect and impossible to fix in post without making hundreds of separate adjustments. Locking things should eliminate the breathing effect and make adjustment far easier.


Brian

 

[RaptorMan]

I've looked into this issue a bit more as I've been editing the video I shot last week and I'm now not so sure this is an AWB issue. And, a better description of the problem than breathing is a pulsing of flickering effect that happens several times per second.

While playing the video from withing Adobe PP with the 'Lumetri Scopes' up and specifically the 'Waveform (Luma)', 'Parade' and 'Vectorsope YUV' displayed this pulsing effect is visible in the scopes. Interestingly, the values over about 50 IRE don't seem to be effected but everything below 50 IRE is. There are times where it looks like everything below 50 IRE is flickering down then up more than once per second and at other times it looks like the upper end of the below 50 IRE pulses upwards while the lower end appears to be pulsing down.

So, the effect is worse when there's video content below 50 IRE and that portion of the video above 50 IRE appears to be unaffected. I'm not sure how AWB could cause that though I will test this as soon as I can. It really looks to me that the camera is doing something with dynamic range that's effecting the lower end up to the middle but not the top of the IRE spectrum.

Sadly, the edited video, where I've adjusted the contrast such that the bottom of the video IRE is brought further down to improve contrast only make this pulsing/flickering effect worse. I'm truly bummed by this...


Brian

 

[Quadpilot]

The flickering is the inevitable result of the H.264 codec using inter frame mode which means that only about 3-4 frames per second are fully recorded, while all frames in between only record the change. When moving fast or flying low, this means that there is a more dramatic change in the frame at each fully recorded point, which when played back at normal speed results in a noticeable flicker.

This has been reported to be less noticeable on the X5R vs the X5, even in the compressed proxy mode recorded to the microSD card, and is of course totally absent on the RAW CinemaDNG footage since every frame is fully recorded.

 

[The Editor]

The flickering is the inevitable result of the H.264 codec using inter frame mode which means that only about 3-4 frames per second are fully recorded, while all frames in between only record the change. When moving fast or flying low, this means that there is a more dramatic change in the frame at each fully recorded point, which when played back at normal speed results in a noticeable flicker.

This has been reported to be less noticeable on the X5R vs the X5, even in the compressed proxy mode recorded to the microSD card, and is of course totally absent on the RAW CinemaDNG footage since every frame is fully recorded.

I 'kind' of agree but have to say that it is more than likely caused by DJI's lack of understanding of codecs and the interplay and importance of bitrate-v-intra frame encoding-v-GOP structure.
The big boys (Sony/Panasonic etc) have been using H264 for a few years now and know what they are doing when it comes to codecs. There is no flickering on their offerings even in the domestic camera world.
DJI are still totally cluless in the imaging arena and it has really shown in the latest efforts at producing cameras.
Even their most recent product the X5R is not really even in the same room as a professional camera and gets by purely on horsepower alone and being able to record raw. However, it lacks a whole plethora of true professional tools that are evident on pro cameras that I would like to see.
To name but a few.......

• Adjustable knee point in both cut off and slope
• Fine tuning of sharpening in both horizontal and vertical axis including frequency and resolution
• Paint control/color matrix profiles
• White balance tracking options
• White balance off-set
• Iris tracking speed adjust
• User definable timecode options
• Angle of shutter selectable over shutter speed

I so wish DJI had got together with one of the big players (and I don't mean their Hasselblad collaboration as they are totally cluless when it comes to video capture) to roll out a professional video imaging device that was a real game changer.
Unfortunately, they appear to have relied on a raw workflow and tried to make people believe that is the utopia of video camera features.
There need to learn....that is only part of the puzzle in putting together a great camera.

 

[RaptorMan]

E and Quad, thanks for the input even if it means there's little one can do to prevent this. I wonder, however, if there are settings that one can use to minimize the problem.

I have noticed that some video looks REAL bad while other video, with seemingly similar content and tonal qualities, appear much better. The video I put up a few days ago called "Johnson Canyon" exhibits some of this but is not a show stopper, but a video I'm now working on is killing me with horrendous flicker. I wish I understood what makes things worse and what makes things better.

I do hope DJI pulls there head out of the *** and either figures this out themselves or pays someone to do so. If you can't control this and don't know when it's going to show its ugly head how can you plan any work with confidence.


Brian

 

[Vladimir]

This note may not be related directly to your flicker problem, but if you get what I call strobing, it may come from lights in the vicinity that pulse at a different rate to your frame rate.

 

[RaptorMan]

This note may not be related directly to your flicker problem, but if you get what I call strobing, it may come from lights in the vicinity that pulse at a different rate to your frame rate.

No, this isn't from lights as it's full on daytime in areas with no people. It's not due to the frequency of a light source unless one counts the periodic fluctuations of the Sun.

It is very likely what the Editor has described about DJI's utter failure to comprehend how to code for video compression. It's also possible that control of white balance and exposure are beyond DJI's skill set as well.

So, we may well be stuck with this garbage forever...


Brian