GH4 Is there anything to be done about banding pixels in blue skies?

A

andrewmfilms

Member
Example:

(I upped the curves so you could see clearly)

banding.jpg

Anything to be done about this? I filmed on a 12-35mm lens and my master pedestal is up +15. Filmed in 4K MP4.
 
Many more expensive cameras will do the same thing If you're concerned about how the GH4 4k is doing with this, use a GH2 for a day and compare! We've come a long way...
 
Reset your master pedestal and see if it helps. Also make sure you're not running any weird image enhancing stuff, like dynamic ir or whatever it's called.
 
Even computer graphics can struggle at that resolution with that subtle of a blue gradient. Just the nature of 8bit images I'm afraid. Even if you could shoot at higher than 8 bits any delivery format is going to potentially bring the banding back again.

Only way to deal with banding in a large area of similar colors like a smooth gradient is to add dithering. Noise is a form of dithering. The dithering effect helps add in random values of the gradient color to break up the banding in the image.

You can dither (add noise) in post but sometimes it is better to shoot the sky with your ISO bumped up a bit to help the camera add some of its own dithering (noise) into the image. This way you have a 14bit dithered image in the DSP that then gets recorded to a rather clean looking 8bit dithered image with much less banding.

I know it seems odd to use a higher ISO outdoors but it really does help. Of course you don't have to go super high with the ISO. Just enough to break up the flatness of the gradient. Sometimes ISO400 helps.
 
David W. Jones said:
+1

absolutely no reason to raise it to +15
Click to expand...

david-

as a gh4 novice i ask in earnest:

(not to start a flame, so thank you in advance)

+15 on the master pedestal seems to be a setting that is often suggested as the "go to".

are you suggesting the +15 master pedestal was inappropriate for an exterior sky shot?

or

are you suggesting that +15 master pedestal "in general" is too much?

lastly, can you share some of your settings and your thinking?

(again, i'm a gh4 lurker trying to understand the cameras strengths.

if this is a topic that merits it's own thread, just say so.

lastly, i apologize in advance if i have inadvertently put you on the spot)

be well.

rob
smalltalk productions/nyc
 
robfilms said:
david-

as a gh4 novice i ask in earnest:

(not to start a flame, so thank you in advance)

+15 on the master pedestal seems to be a setting that is often suggested as the "go to".

are you suggesting the +15 master pedestal was inappropriate for an exterior sky shot?

or

are you suggesting that +15 master pedestal "in general" is too much?

lastly, can you share some of your settings and your thinking?

(again, i'm a gh4 lurker trying to understand the cameras strengths.

if this is a topic that merits it's own thread, just say so.

lastly, i apologize in advance if i have inadvertently put you on the spot)

be well.

rob
smalltalk productions/nyc
Click to expand...

No problems Rob.

Folks are using the ped to try and emulate a log profile to squeeze as much dynamic range as they can out of the GH4, which is fubar.

The master pedestal should be used to match the black level of other cams in multi cam shots, or make minor adjustments. It is not a substitute for a log profile. Just because you can raise the ped to +15 doesn't mean it is a good idea. I have a feeling that if some of these "camera gurus" posted that you should raise your saturation level all the way up when you shoot, and then drop it back down in post, hundreds of sheep would be shooting that way.

It looks like Panasonic is working on a log profile for the GH4, which combined with the 10bit 4:2:2 4K output into say the Shogun should be the tits.
 
David W. Jones said:
No problems Rob.

Folks are using the ped to try and emulate a log profile to squeeze as much dynamic range as they can out of the GH4, which is fubar.

The master pedestal should be used to match the black level of other cams in multi cam shots, or make minor adjustments. It is not a substitute for a log profile. Just because you can raise the ped to +15 doesn't mean it is a good idea. I have a feeling that if some of these "camera gurus" posted that you should raise your saturation level all the way up when you shoot, and then drop it back down in post, hundreds of sheep would be shooting that way.

It looks like Panasonic is working on a log profile for the GH4, which combined with the 10bit 4:2:2 4K output into say the Shogun should be the tits.
Click to expand...

+1

Cinelike D isn't log. It's pretty good and I shoot 90% of the time with it. Trying to make it log is a mistake and just messes up the image. V-LOG will be interesting but to make it a real log profile Panasonic has to update the color science of the camera and I think they will. Hopefully it will improve the color on all the profiles too.
 
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I'm really not a fan of shooting ultra-flat profiles on 4:2:0 8-bit unless the camera has been designed to do it.

You've got very limited dynamic range in the encoding, no matter what's coming off the sensor.

Proper log profiles use a known, well-defined way of mapping the sensor output to an intermediate packed state knowing that an inverse transform is going to be used at the other end to recover maximal information.

Whapping up the master pedestal by +15 just adds a constant offset to the signal and further squeezes your limited range. In this case presumably taking it from 255 grey levels down to 240.

In no way is that a good idea.

If you shoot clear blue skies a lot, I'd suggest a day of testing profiles. See what the contrast, curves and profiles give you. Try higher ISO- the lowest ISO settings are sometimes artificially "squashed", losing a stop or more of dynamic range. A little bit of noise is your friend, it can offset banding as others have said.

When I had an AF100 I never really cracked a profile that matched my RED or avoided hideous banding on plain walls.

I'm glad to say it's been a completely different story with the GH4. Natural profile with Contrast -3, Sharpness -4, Shadows +1 seems to be a good match to Redcolor3/Redgamma 3. So I end up only doing gentle corrections or overall looks in the grade, rather than trying to undo an ad-hoc attempt to create a log profile first.

I've not had major problems with banding so far. I've seen hints a few times, but NOTHING like the scale of the AF100. Granted I'm shooting 4K for HD delivery, which helps. A lot.

But hooray, rejoice in the GH4's 10-bit 4:2:2 output to external recorder. If banding becomes a major issue, at least a proper solution is imminent.
Cheers, Hywel.
 
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Yea, your JPEG-like 8 bit image is starved of bit-space as it is, and don't forget the tone curve is already baked in unlike a raw file. Please don't make it super flat. Get 80% right in the camera then do the 20% in post. Doing it the other way around requires a raw process.
 
Looking at this from an underwater perspective. (Banding in the blue/green)

It appears to be mainly on the Blue Channel - is there anyway in FCPX to apply filters/corrections (dithering / then blur etc) to certain channels? (not talking color masks)
 
Master pedestrial affects black level and dark tones. It does very little to colored parts of image like blue sky. If using +15 blacks become gray of foggy due to raised black level. Sometimes it is handy but usually it is not a good idea to limit black level much.

Shooting 0-255 can reduce banding, also NR -5 and little reduced color helps.
 
TheTrickster said:
Looking at this from an underwater perspective. (Banding in the blue/green)

It appears to be mainly on the Blue Channel - is there anyway in FCPX to apply filters/corrections (dithering / then blur etc) to certain channels? (not talking color masks)
Click to expand...

Use a filter. As in, a physical filter over the lens/housing.

I'm not a diver so I'm less knowledgeable about what filter to use, but I believe you may need to match the strength of the filter depending on your dive depth.
 
yslee said:
Use a filter. As in, a physical filter over the lens/housing.
Click to expand...

Alas, this isn't anything to do with the use of filters, which you are correct, you need different ones for different depths. This just helps with colour balance not banding.

This is the same issue as blue sky gradients, but just darker bluer/green.
 
Back when I used JPEG-only digital cameras a colour correction filter helped with bit-depth issues.
 
When I watch TV programs with very low bitrate there is less banding in skies than in GH4 100 Mbs 4k files. I think 4:2:0 is not limiting color steps, it just reduces color resolution. If I render a photo slideshow in 8bit 4:2:0 video there is no banding.

Samples: http://www.dpreview.com/forums/post/57394235


Has the Panasonic codec less "colors" than others? Or is there a differences in color channels? Does the sharpen 0 cause banding? How about contrast setting?


I have heard that Panasonic cameras records green colors better than other cameras but has difficulties in skin tones (reds) and skies. GH4 renders nature greens beautifully and sharply. Also the red "spill" or spread over real details is minimal in GH4. A friend said that his Nikon makes less banding in sky than GH4.


It is impossible to know what camera makers do when they down scale their sensors and tries to get small enough data rate for video.
 
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