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High levels of Noise on videos on Manual mode, at ISO 100, LOG mode and without filters. Please Help.

Raul3d

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I'm confused as even when I shoot video at ISO 100, in LOG mode and without any filters, if the sun has gone down as you can see in the video before, I get a high amount of noise.

https://youtu.be/kx9hIwFD9iY

Can someone tell me why that is? And how i can avoid getting that? I'm shooting in manual mode and should be able to control all aspects of this.

Thanks in advance.
 

Raul3d

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Frame rate is 30 frames per second.... And my shutter speed is at 60 fps.
 

CanadaDrone

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Does it look like that in 100Mbps straight off the drone when you view it on your computer? YouTube usually reduces the quality substantially and introduces artifacts.

In your sample, the foreground is very underexposed, which means you are not filling the photosites on that tiny little 1/2.3" sensor with light, and the result is increased noise - shadows are never going to look perfectly clean in a scenario like this. You can see the areas of the sky that are properly exposed have virtually no noise.

You could try a graduated ND filter for stuff like this, which will help you expose for both the foreground and sky creating a psudo-HDR effect, but then you can't change the horizon line without getting uneven footage. A camera sensor can only expose for one thing at a time, so when you are shooting a scene like this with such a high dynamic range, you can only have one of the two areas exposed properly.
 
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CanadaDrone

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Unfortunately it looks like that when I open it on VLC from the original file so it's not Youtube.
The foreground is underexposed as I was trying to expose for the sky, I didn't realize that underexposing would create noise. I guess I should have used then my 4 or 8 ND filter and exposed for the foreground ?
Yes, underexposing always creates noise. The reason is that each photosite on the sensor has what's called a full well capacity - the ADC will report a maximum value at base ISO when FWC has been reached, or in other words when the photosite has been fully saturated with light/electrons to its maximum capacity. If you are only feeding each photosite half the light that it needs to make an ideal, noise-free exposure, you get noise (noise appears randomly within an image). Alternatively, when you raise the ISO you are essentially telling the ADC to report max code at a lower electron count, which again as we all know increases noise (higher ISO = more noise). For a numerical example, lets assume for argument's sake FWC on the Mavic Air's sensor is 100,000 electrons at ISO 100. At ISO 400, the ADC is told to be satisfied and report maximum code after capturing only 25,000 electrons, and digital amplification is applied. That is the basic physics behind it anyway.

If you used a normal ND filter (or no filter at all) and exposed for the foreground, you would run into exactly the same problem, but the opposite (foreground properly exposed, but sky totally blown out). No matter what you do, the sensor can only expose for one exposure at a time - when you shoot a scene with dramatically different brightness levels (like a sunset over dark foreground) you have to pick one or the other. A standard ND filter would do nothing to help you at all but you can use whats called a graduated ND filter - these allow half the ND filter to expose more, and half to expose less. You would put the transition point on the horizon, and you could even out the scene by darkening the sky while exposing for the foreground. The problem with these filters on drones is that you can't adjust them in the air, so you would have to plan your entire flight around it, and never alter your position relative to the horizon unless you wanted very uneven footage.
 
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Raul3d

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Yes, underexposing always creates noise. The reason is that each photosite on the sensor has what's called a full well capacity - the ADC will report a maximum value at base ISO when FWC has been reached, or in other words when the photosite has been fully saturated with light/electrons to its maximum capacity. If you are only feeding each photosite half the light that it needs to make an ideal, noise-free exposure, you get noise (noise appears randomly within an image). Alternatively, when you raise the ISO you are essentially telling the ADC to report max code at a lower electron count, which again as we all know increases noise (higher ISO = more noise). For a numerical example, lets assume for argument's sake FWC on the Mavic Air's sensor is 100,000 electrons at ISO 100. At ISO 400, the ADC is told to be satisfied and report maximum code after capturing only 25,000 electrons, and digital amplification is applied. That is the basic physics behind it anyway.

If you used a normal ND filter (or no filter at all) and exposed for the foreground, you would run into exactly the same problem, but the opposite (foreground properly exposed, but sky totally blown out). No matter what you do, the sensor can only expose for one exposure at a time - when you shoot a scene with dramatically different brightness levels (like a sunset over dark foreground) you have to pick one or the other. A standard ND filter would do nothing to help you at all but you can use whats called a graduated ND filter - these allow half the ND filter to expose more, and half to expose less. You would put the transition point on the horizon, and you could even out the scene by darkening the sky while exposing for the foreground. The problem with these filters on drones is that you can't adjust them in the air, so you would have to plan your entire flight around it, and never alter your position relative to the horizon unless you wanted very uneven footage.
I see, thanks for the explanation! I will try that next time...
 
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