Andreabetlem
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Joined: Mon Jun 14, 2021 11:22 am

Meaning of ISO-6

Mon Jun 14, 2021 11:29 am

Hello,
I am doing a research project and I comparing different ISOs in the picamera. After having my code executed, which had the ISO set to automatic (ISO-0), I could see the picture with the maximum exposure time has an ISO-6 but i don't understand what this means. Could anyone please help me figure it out?

Thank you so much,

Andrea

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B.Goode
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Re: Meaning of ISO-6

Mon Jun 14, 2021 11:47 am

Andreabetlem wrote:
Mon Jun 14, 2021 11:29 am
Hello,
I am doing a research project and I comparing different ISOs in the picamera. After having my code executed, which had the ISO set to automatic (ISO-0), I could see the picture with the maximum exposure time has an ISO-6 but i don't understand what this means. Could anyone please help me figure it out?

Thank you so much,

Andrea
Perhaps doing meaningful research needs learning to pose meaningful questions?

What camera? What Operating Sytem? What is "my code"? How are you measuring the reported ISO?

Official Raspberry Pi documentation here - https://www.raspberrypi.org/documentati ... /README.md and https://www.raspberrypi.org/documentati ... /camera.md

drgeoff
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Re: Meaning of ISO-6

Mon Jun 14, 2021 6:25 pm

Andreabetlem wrote:
Mon Jun 14, 2021 11:29 am
Hello,
I am doing a research project and I comparing different ISOs in the picamera. After having my code executed, which had the ISO set to automatic (ISO-0), I could see the picture with the maximum exposure time has an ISO-6 but i don't understand what this means. Could anyone please help me figure it out?

Thank you so much,

Andrea
Writing things such as "the picture ... has an ISO-6" suggests that you haven't bothered to search for or read information such as https://photographylife.com/what-is-iso-in-photography
Quis custodiet ipsos custodes?

Jack Hogan
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Contact: Website

Re: Meaning of ISO-6

Tue Jun 15, 2021 9:36 am

Andreabetlem wrote:
Mon Jun 14, 2021 11:29 am
Hello,
I am doing a research project and I comparing different ISOs in the picamera. After having my code executed, which had the ISO set to automatic (ISO-0), I could see the picture with the maximum exposure time has an ISO-6 but i don't understand what this means. Could anyone please help me figure it out?

Thank you so much,

Andrea
I don't know why your question was taken to be such an offence: I also saw that ISO-6 popping up and always thought it was probably a misnomer or a mistake.

Most consumer cameras are designed so that the sensor will just start to clip around 1 lx-s of Exposure at base gain, which is often indicated as ISO100. ISO6 would in that case imply that the camera needs an Exposure of 16.67 lx-s (100/6) to reach full scale, which is a physically unreasonable amount of exposure for typical photographic applications.

Unfortunately the relative ISO standard (ISO 12232:2019) is not helpful, so you will find no solace there. If you would like to better understand how the sensor responds I suggest that you turn all automatisms off and take manual control of Exposure and gain, ideally with raw captures. From memory, in raspistill you can start with -ex off, -awb off -ag 1 -dg 0 and choose a suitable shutter speed for your scene, in picamera there must be similar options. Then vary -ag, which is the active ingredient of what is referred to as ISO in photography. I did something similar here:

https://www.strollswithmydog.com/pi-hq- ... rformance/

Jack
Last edited by Jack Hogan on Tue Jun 15, 2021 10:31 am, edited 1 time in total.

jamesh
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Re: Meaning of ISO-6

Tue Jun 15, 2021 9:40 am

drgeoff wrote:
Mon Jun 14, 2021 6:25 pm
Andreabetlem wrote:
Mon Jun 14, 2021 11:29 am
Hello,
I am doing a research project and I comparing different ISOs in the picamera. After having my code executed, which had the ISO set to automatic (ISO-0), I could see the picture with the maximum exposure time has an ISO-6 but i don't understand what this means. Could anyone please help me figure it out?

Thank you so much,

Andrea
Writing things such as "the picture ... has an ISO-6" suggests that you haven't bothered to search for or read information such as https://photographylife.com/what-is-iso-in-photography
Please keep it civil.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Working in the Application's Team.

drgeoff
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Joined: Wed Jan 25, 2012 6:39 pm

Re: Meaning of ISO-6

Thu Jun 17, 2021 1:37 pm

A picture does not have an ISO number. Originally it was a measure of film sensitivity but later the concept was adopted for digital sensors/camera. Reading anything semi reliable on the internet should have made that clear.
Quis custodiet ipsos custodes?

Jack Hogan
Posts: 118
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Contact: Website

Re: Meaning of ISO-6

Thu Jun 17, 2021 4:11 pm

drgeoff wrote:
Thu Jun 17, 2021 1:37 pm
A picture does not have an ISO number. Originally it was a measure of film sensitivity but later the concept was adopted for digital sensors/camera. Reading anything semi reliable on the internet should have made that clear.
I think what is clear is the reference to the ISO value recorded in the file that produced the 'picture', not everybody's first language is English. His question is valid, perhaps you would like to address it:

Where do ISO values written by the Pi software in camera files come from?

'Cause ISO-6 does not make any sense to anyone who understands what ISO stands for in digital photography, including me.

6by9
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Re: Meaning of ISO-6

Thu Jun 17, 2021 5:25 pm

Without a file to analyse, or the code being used to generate those files, it's near impossible to say what is going on.

It could be a parsing error in EXIF reader, or some weird combination of settings that cause the firmware to write an odd value. However playing guessing games as to what is going on is a waste of time.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

Jack Hogan
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Contact: Website

Re: Meaning of ISO-6

Thu Jun 17, 2021 7:32 pm

Here's an easy question that you should be able to answer and will probably lead you in the right direction: how is the ISO value generated in raspistill with manual exposure? With the - r switch?

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