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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Noise in the blacks

E

Eugene Lehnert

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I'm assuming this type of noise is caused by underexposed areas of the image? I debayered this image at 4K and when it is viewed on an HD monitor I get this pattern. When downconverted to 2k the pattern goes away. Is this a low-light issue with the bayer sensor?

Thanks.
 

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Eugene Lehnert said:
I'm assuming this type of noise is caused by underexposed areas of the image? I debayered this image at 4K and when it is viewed on an HD monitor I get this pattern. When downconverted to 2k the pattern goes away. Is this a low-light issue with the bayer sensor?

Thanks.
Click to expand...

That looks like the sensor pattern. I've only seen it when a black shade fails or when a black calibration wasn't performed and was shooting in low light with available light. It's not a fault of the camera, mostly user error.
 
I am viewing this inside of Nuke at the moment. It appears on the HD monitor when outputting 4k but in 2k it looks fine.
 
It only happens when the image is divided between 1.5 and 1.9 in the viewer. I guess at these sizes the noise creates this pattern.
 
This is an artifact that can be introduced by a cheap scaler (such as often used by monitor pipes). You should not see this when rendering out using a high quality scaler.
 
I just started using Nuke for the denoise filter and I noticed it as well, but because I am new to Nuke, I don't know how to export the video yet. If you have any tutorials to point me toward on how to export it would speed things up. ;-)
However, I think it's just a display thing in Nuke, also the denoise seems to work great. I haven't been able to figure out how to use Denoise in RedCineX yet either.
 
Use a write node to export your clip.
 
The denoise in RedCineX only applies to chroma. From my tests, it looks like it applies a subtle blur to the red and blue channels.

Graeme Nattress said:
The denoise in RCX is chroma-NR that works on full demosaic only. As I can't really see chroma noise in the dark shadows, it's not surprising you're seeing little effect. The chroma denoise works well when chroma noise is quite visible, otherwise you won't see it. Those darkest shadows are over 8 stops down from clip, and you're seeing a mild organic grain-like effect. I'm not worried.

Graeme
Click to expand...
 
Under exposed way to far, over sharpened way to much... What did you expect...

Have seen it in internal tests here with the same results when we are pushing 2k images to the absolute extremes an over sharping them to the extreme... Doing silly things that you would never need to do in the real world.

Not sure what the point of this post is...
 
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