Sensor characteristics : where are the data for linearity

[christian viladrich]

Hi,

I have SharpCap Pro. I am testing sensor linearity in order to make accurate measurement of filters transmission profile.

With the "sensor characteristics" tool of SharCap, it is possible to measure a number of characteritics of sensor including linearity.

With the Pro license, it is possible to export the resulting data, except data on linearity of the sensor.

Is there a way to export the data on linearity of sensor ? By data, I mean the complete table (ADU/exposure time) as measured by SharCap.

Basically, I would like to analyse further the measurements made by SharpCap, a bit like this :
http://www.astrosurf.com/buil/CMOSvsCCD ... mm-683.png


But for this, I need to get the complete table (ADU/exposure time) as measured by SharCap. Is this table saved somewhere ? Is it possible to export it ?

Thanks for you help !

[Jean-Francois]

Bonsoir Christian,

The sensor characteristics are saved here: C:\Users\xxxxx\AppData\Roaming\SharpCap\SensorCharacteristics
You can copy the files (one per camera type and bit) on different computer without redoing the sensor analysis.

Salutations,
Jean-François

[christian viladrich]

Bonsoir Jean-François,

The file under C:\Users\xxxxx\AppData\Roaming\SharpCap\SensorCharacteristics"is a bin file.
It is possible to read this file with the smart historgram of SharpCap, but the only data available is the table :
- gain value,
- e/ADU,
- read noise,
- FW,
- relative gain,
- dynamic range

So my question, where is the data about linearity of the sensor saved ?

Thanks,

Christian

[Jean-Francois]

Bonsoir Christian,

The files *.json are text files ... you can open it with an editor ... for example:

{
"BitDepth": 12,
"IsAdditiveBinning": true,
"LinearityLimit": 0.90966976,
"CameraType": "QHY Cameras",
"IsMono": true,
"IsRaw": false,
"SensorName": "QHY174M",
"ColourSpace": "MONO16",
"CameraMode": null,
"GainList": [
{
"OffsetInfo": [
{
"OffsetValue": 0,
"MeanADU": 16.157476,
"MedianADU": 16.0,
"SigmaADU": 1.6150199
},
{
"OffsetValue": 51,
"MeanADU": 813.8816,
...
...

If you search only the "upper" limit of the linearity ... it could be the "LinearityLimit" at the beginning of the file.
In my case of my QHY174-GPS camera = 0.91 ... could mean 91% of the full bit depth.

If not ... may be SharpCap recalculate the linearity from the available data.

Good night,
Jean-François

[christian viladrich]

Bonjour Jean-François,

Thanks for your time !

After having a closer look to this *.json file, it seems to me that the only onformation about linearity there is the "LinearityLimit".

I have not seen any data about the table : (ADU/exposure time) used to calculate the LinearityLimit.

Or maybe this data is in another file ?

It would be nice to have this data in order to work on it.

Thanks,

Christian

[admin]

Hi folks,

it should write a csv file to your desktop with the actual linearity measurements in. Do be careful in reading too much into this figure though - the biggest cause of low values is very definitely variations in the illumination level during testing rather than anything related to the sensor itself.

cheers,

Robin

[christian viladrich]

Hi Robin,

Great ! Now you say it, I can see the files on my deskstop. I was blindly looking somewhere else.

No problem with the illumination level, I have a stabilized lamp.

Many thanks for this beautifull software !

Christian