Can Canon cameras support pixel binning? - page 2 - RAW Shooting and Processing - CHDK Forum

Can Canon cameras support pixel binning?

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Re: Can Canon cameras support pixel binning?
« Reply #10 on: 17 / August / 2016, 02:02:02 »
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I follow your thread with much interest….

So for this camera where I have measured standard deviation as 54.1 for ISO6400 (after black level subtraction), it would be reduced to 19.3, which is about the level of ISO3200.

Where do you get the black level? Do you get the black level from RAW?
As I know from my G1x, the black level changes on higher ISO.

What about dead pixel? Does dcraw remove this pixel?

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Re: Can Canon cameras support pixel binning?
« Reply #11 on: 17 / August / 2016, 10:46:47 »
Code: [Select]
    white    black
iso    max    min    max    avg    std    max    blk lvl
80    3969    0    48    .940    1.14   
200    3967    0    49    1.60    2.26    4092    126
400    3964    0    103    2.78    4.03    4091    127
800    3960    0    119    5.16    7.38    4089    129
1600    3954    0    175    9.83    14.2    4084    131
3200    3941    0    409    18.3    27.1    4074    134
6400    3954    0    746    36.7    54.1    4095    143

What this table means
ISO - The ISO of the picture. Tv was 1/50s.
White - the max decoded white pixel, under a bright lamp.  This is the max raw value minus the black level.
Min black - the darkest pixel found in the active area.  When it reaches 0, it means the variance from black level is so extreme, that the pixel tries to go out of range.  You should be careful of estimating any statistics in this condition as the distribution is cut off.
Max - the max pixel value with the lens cap on. We call this a dark frame.
Avg - the measured mean of the active area. This is not the same as the estimated mean of the distribution, in the case that the minimum value is zero, because the tail is cut off.
STD - the standard deviation. This is a measure of noise mathematically, but not how your vision perceives noise.  What it means is how much +- from the mean, that 68% of the pixels will differ.
Max - the 2nd max is where I added the white max to the black level to find the raw sensor max.  This should never exceed the bit depth of the sensor, so 4095 but a 12-bit sensor.
Blk Lvl - the black level as found by rawdigger. Probably just the mean of the masked area.

How to use this table
For example, averaging pixels through binning has a formula for how it reduces noise, as std/sqr(n).  So if my std is 54.1, and I average 16 pixels, the new noise level is 54.1/4=13.5.  Now you can look in the table and see that's the same level as ISO1600, so you can say more simply that binning of 4 superpixels reduces (mathematical) noise by 2 stops.

There is a slight effect that increasing ISO is less noisy than expected.

I'd rather suggest that we talk about this over at
https://chdk.setepontos.com/index.php?topic=12926.0

because I've answered the question about binning. 

About binning: my impression is that it's kind of a myth, people hear about it and it's a feature in some cameras that are supposed to do amazing things, so they are looking to replicate that benefit somehow.  What I'm hoping to do with experiments is show that binning is nothing magical, it's almost the same as resizing any image in any software to half/quarter etc. of the size.  This benefit is rather obvious, as merging any n pixels together in someway always reduces noise.  But is this any better than wavelet, NL Means, or other famous algorithms?  At the moment, I don't even see what benefit it has from doing it in hardware, except for no quantization errors in adding the pixels.


Re: Can Canon cameras support pixel binning?
« Reply #12 on: 17 / August / 2016, 10:54:49 »
My camera has no dead pixels or stuck pixels, as you can see from the statistics table, the min/max values are in a reasonable range and increase always with ISO, so all pixels are responding.  The worst pixels are in the masked area, where some are stuck to certain values.

How does dcraw handle deadpixels? Just look in the manual for some clue:
Quote
-P deadpixels.txt Read the dead pixel list from this file instead of ".badpixels". See FILES for a description of the format.

Raw therapee and other programs have options to automatically detect them and interpolate around them, so nothing to worry about.

Re: Can Canon cameras support pixel binning?
« Reply #13 on: 17 / August / 2016, 11:14:54 »
Working out this imagemagick command was actually pretty important, so I don't need rawdigger anymore, to measure raw stats.  I needed to separate the pixels by colour to see how WB affects the noise levels.  I can do all the things I needed rawdigger for now, for free.


 

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