[Elphel-support] 答复: 答复: 答复: 答复: 答复: 答复: sync stereo with lidar

[Allen Yin]

Hi Andrey,

If I want to get gamma conversion parameters from EXIF data , can I use “identify” command in Linux?  Or I can only use ImageJ plugin.

I try to use ImageJ and plugin, it’s difficult to setup the environment.

Attached is  EXIF data get by “identify”, how to get the gamma value?

Thanks,

Allen Yin

发件人: Elphel Support <support-list at support.elphel.com>
发送时间: 2018年3月8日, 星期四 10:37
收件人: Winston Zhang <winston.zhang at blacksesame.com.cn>
抄送: Elphel Sales | Olga Filippova <sales at elphel.com>; Tao Zhang <tao.zhang at blacksesame.com.cn>; Qun Gu <qun.gu at blacksesame.com>; Pioneer Li <pioneer.li at blacksesame.com.cn>; Allen Yin <allen.yin at blacksesame.com.cn>
主题: Re: 答复: 答复: [Elphel-support] 答复: 答复: 答复: sync stereo with lidar

Hello Winston,

Tomorrow Oleg will try to reproduce your settings - so far we did not have such problems.

BTW, you can set same parameters on multiple ports simultaneously, using "Broadcast Mask" (hex number 0..f)
Port 0: 1
port 1 - 2
port 2 - 4
port 3 - 8,

So broadcast mask 3 will set the same mode on ports 0 and 1.

About bits I tried to explain in the previous messages and the "How many bits..." in the article.

Sensor provides 12 bits, and each bit is important in the shadows. But not in the bright light because of the shot noise that is caused just by the fact that each pixel can store only integer number of electrons. And so while all bits are important, there are not 4096 meaningful levels for each pixel, but significantly less (see "How many bits..."). Gamma conversion uses non-linear scale to represent pixel values with steps proportional to the shot noise (steps are smaller). The gamma conversion parameters are saved in the Exif header of the JP4 file, and if you open files with ImageJ plugin, it takes care of the Exif data and restores linear data proportional to the pixel raw values, then you can save it as  32-bit Tiff file.

Andrey




> Hi, Andrey
> I met a new question. I set ‘Color’ parameter with the five(it could get the jp4 format image)on one camera, and this camera image format was converted. But when I set the other one, this camera image format was not converted. Please help me test for it.
> Another question
> What is the raw jp4 format image with 100% compression bit wide? I read it and the result show the bit wide is uint8. But you web shows that the bit wide is 12bit.
>
>
>
>
> Best Regrad!
> Yicheng-Zhang
> Email: winston.zhang at blacksesame.com.cn<mailto:winston.zhang at blacksesame.com.cn>
> Teil: 18516291005
> Addr: 707 room, 7th floor, building 4th, No.1761, Zhangdong road, Pudong area

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