Existing internal processing and adjustment ​using RAW format?

[Gilad Weil]

Hi

As part of a vegetation monitoring program in nature reserves, I examine changes by using a time series of photos. I use a modified rebel i3, in which the internal IR filter has been removed (http://www.maxmax.com/ircameraconversions.htm). I use a series of external filets in order to sample in different wavelength. I use fixed WB, shutter speed and RAW format only.

I dont need a "good looking" picture - I need the original data with minimal Intervention of the camera.

But my question has to do with the image processing – since the results I get aren't good enough:

1.I am interested in the raw values ​​of the radiation – Is there any additional processing in RAW format, such as balancing blue green and red (the sensor was double green detectors, any effect?), or adjustment in the case of saturation of the sensor?
2.Where can I find quantitative data (not picture) about the behavior of the sensor along the spectrum?

Thanks!

Gilad Weil

Remote Sensing,

Nature and Park Authority

 

[Jim Saunders]

This could be interesting...

Jim

 

[dgatwood]

I suspect it depends on the software doing the processing. The camera records lots of data in EXIF (e.g. WB data), which the processing software uses when determining how to compute the color value for a given output pixel from the raw data. And the software doing the processing is, of course, free to ignore that outright and substitute its own interpretation of the values.

How are you pulling the values from the RAW file?

 

[Gilad Weil]

Thanks! :
I have a background in image processing, especially of satellite imagery. I use image processing software such as ENVI and extensions of ARCGIS.
I actually need to understand the process of converting the radiation received on the sensor to the RAW file - is the RAW file really the RAW data?
In addition, data describing the sensitivity of the sensor (R, G, B) through the spectrum would help me a lot, as well as understanding the issue of the effect of the ratio between the CCD RGB receptors (1:2:1).
Gilad

 

[Skulker]

For such a specific application you might get some data from canon. I suspect you will have do some tests to determine sensor performance and raw output. You may well need to read the raw files directly, rather than using a raw converter. Thinking of raw converters they all make the conversions differently (I'm talking algorithms for those that like long technical sounding words : ), so you may need to talk to them as well. I'mwondering what your ttrying to record that needs so much data?

 

[Gilad Weil]

Thanks ???

I use the RAW file itself, without conversion.
I produce NDVI index from the differences between the Red to IR http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index

 

[Skulker]

Thanks ???

I use the RAW file itself, without conversion.
I produce NDVI index from the differences between the Red to IR http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index

so why do you state you use the same WB? I sense a disconnect between reality and forum world.

 

[weixing]

Hi,

I actually need to understand the process of converting the radiation received on the sensor to the RAW file - is the RAW file really the RAW data?
In addition, data describing the sensitivity of the sensor (R, G, B) through the spectrum would help me a lot, as well as understanding the issue of the effect of the ratio between the CCD RGB receptors (1:2:1).
Gilad

Not sure what you looking for, but this website might help you: http://www.astrosurf.com/buil/cameras.htm (some of them not in english). Anyway, I think you should check with the Astronomy forum (such as cloudynights) as many Astrophotographer use mod Canon DSLR for imaging.

Have a nice day.

 

[Busted Knuckles]

My suggestion is go and hang out with Alex1 over on the Magic Lantern website - sorry for the redirection - but diving into what the camera is really doing and fiddling w/ the programs, sensor readings, etc, etc. He is likely to have some insight.

 

[dgatwood]

Well, IIRC, Canon's RAW files contain an embedded JPEG rendering, so depending on how your tools pull data from the file, you may or may not be getting the actual raw sensor data.

 

[Mt Spokane Photography]

Hi

As part of a vegetation monitoring program in nature reserves, I examine changes by using a time series of photos. I use a modified rebel i3, in which the internal IR filter has been removed (http://www.maxmax.com/ircameraconversions.htm). I use a series of external filets in order to sample in different wavelength. I use fixed WB, shutter speed and RAW format only.

I dont need a "good looking" picture - I need the original data with minimal Intervention of the camera.

But my question has to do with the image processing – since the results I get aren't good enough:

1.I am interested in the raw values ​​of the radiation – Is there any additional processing in RAW format, such as balancing blue green and red (the sensor was double green detectors, any effect?), or adjustment in the case of saturation of the sensor?
2.Where can I find quantitative data (not picture) about the behavior of the sensor along the spectrum?

Thanks!

Gilad Weil

Remote Sensing,

Nature and Park Authority

The RAW data is processed into a tif image with additional proprietary canon information about the camera settings. There is processing on the sensor for NR.

You will not get the actual output from the sensor.

However, as someone mentioned, check with magic lantern. The information is probably possible to get at with a custom firmware, since the conversion to a image format takes place in the processor under control of the firmware and not in the hardware.

I believe that some labs and universities have hacked their cameras to get at the sensor information.

 

[Lightmaster]

another thread that doesn´t really belong here.
no rumor, not really about camera bodys.

are the mods asleep? ;D