Why does ETC mode introduces more noise.

H

hazna

Active member
Every clip I have shot and every clip I have seen has more noise then in regular mode.
Anybody knows why?
 
I did read the article when it came out.
I am aware of the noise in ETC over 320 iso.
I get A LOT of noise in 160iso in dark areas.
 
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I am sure it has nothing to do with the AVCHD which works the same in both modes.
It must be something the sensor is doing when magnifying in to the sensor.
 
my guess is that the noise on the pixels is the same size as the pixels. Because theres no scaling of the image, but when your not using the ETC you see noise after its been scaled down, subpixel noise (kinda). so ETC has larger noise...

but... ive used it and its freaking awesome!
 
I agree it is awesome. Even scaled down to original the noise looks excessive in dark places.
 
what iso are you at?
To be honist ive never used it and had to push it to far... i normally shoot with a lens f2.4 or below. that helps
 
ISO 160 lenses from F1.2 to F4 in different light.
Always bad results. I will try to find samples.
 
It doesnt magnify the sensor, it uses a technique called "windowing" which uses a small area in the center of the sensor, although with programmable cameras the windows can be any size at any area on the sensor. The noise you observe is the same noise you would get if you shot a raw still and then cropped a 1080 window out of it and viewed that fullscreen. If you want the benefits of a smaller sensor size then you will lose the benefits of the binning/sampling that normally occurs when the camera attempts to compress 16Mp into 2Mp.
 
That is what I meant by magnifying.

Noise is way more then the picture and only in dark areas. I am sound mixing today but tonight will uploads some samples.
 
+1 to what I.breyers said. Squishing the image from 16Mp down to 2Mp smooths away much of the noise in the raw signal.

And, to go off topic for a moment, this is why the people who bleat on about the DXOmark score being marginally lower for the GH2 than the GH1 are lame. Our video footage is processed, not RAW, from the sensor. The GH2 has twice or more the processing power of the GH1 and in normal mode it uses that power to tweak image quality. Whereas in ETC mode what we see is closer to the noise level of the raw sensor.
 
there are plenty of denoising algorthms, commerical or for avisynth, that can help the situation. If you really want to use etc instead of just getting a cheap extender then just do some processing to make up for it. Id be curious to see which route is better.
 
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