Hi Andrey,

Could we bypass the “gamma” module in the FPGA?  We want the original raw data 
from sensor.


Allen Yin

发件人: Elphel Support <support-list@support.elphel.com>
发送时间: 2018年3月22日, 星期四 23:23
收件人: Allen Yin <allen....@blacksesame.com.cn>; Elphel List 
抄送: Pioneer Li <pioneer...@blacksesame.com.cn>; Tao Zhang 
<tao.zh...@blacksesame.com.cn>; Qun Gu <qun...@blacksesame.com>; Winston Zhang 
主题: Re: [Elphel-support] 答复: 答复: 答复: 答复: 答复: sync stereo with lidar

~/.imagej/Eyesis_Correction.xml is not really needed - it just hides/reveals 
some experimental buttons on the interface
This is the contents of such file:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd";>
<comment>last updated Thu Sep 08 14:09:47 MDT 2016</comment>
<entry key="ADVANCED_MODE">False</entry>
<entry key="DCT_MODE">False</entry>
<entry key="MODE_3D">False</entry>

result.jpg looks correct. It should be super-contrast as it is linear, so it 
CAN NOT be saved as JPEG - it needs either 16 bits or 32 bit TIFF as when you 
save it from imageJ (save as tiff). And it is "monochrome" - each pixel 
corresponds to the sensor pixel value. For you application I would recommend to 
use just green subchannel (checkerboard pattern, half of all pixels) - in that 
case you do not need to have aberration correction.

Your plots for gamma seem correct too, to be sure I need to look into the code 
again - I wrote that part several years ago.

Gamma is not changed automatically in the camera, but you may change it using 
one of the interfaces - camvc of just parsedit. In addition to the power (0.57) 
there is another parameter - dark level - the sensor adjusts its ADC to have 
output level of 160 (on 4096 scale) or 10(256) for the complete darkness, 
so-called "fat zero".

Gamma is applied inside the FPGA and parameters are saved in the Exif header, 
so for processing it is possible to "undo" gamma and restore linear scale.


---- On Thu, 22 Mar 2018 00:58:53 -0700 Allen 
Yin<allen....@blacksesame.com.cn<mailto:allen....@blacksesame.com.cn>> wrote 
Hi Andrey,

There seems to be an another error, “2.jpg”.

I have some doubts, could you please help me?

1.     Does gamma value remain unchanged when camera works ?  Who realize this 
gamma mapping, sensor or ISP?

2.     When gamma0 = gamma1 = gamma2= gamma3 = 0.57, gamma_scale0 = 
gamma_scale1 = gamma_scale2 = gamma_scale3 = 1024,

gamma mapping  is  Vout = a*Vin^gamma, a = 2.23  gamma = 0.57 , is it right? If 
not right, could you tell me the right? I use this gamma curve to convert the 
12bit raw data, “result.jpg” is the result.

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