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Originally Posted by Itchy
Paul and Scott
I have just got word back from Mike Unsold (author of ImagePlus). He says (as I thought) that the digic camera settings have no effect on the image with Linear RAW conversion.
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Hi Itchy,
I beg to differ, page 55 of my Canon Manual appears to say the opposite. It says "the image you capture can be processed automatically by the camera in accordance with the parameter settings.... Contrast, Sharpness, Saturation and Color Tone..."
Linear conversion has nothing to do with the camera parameter settings, it is two different subjects. The in-camera parameter settings are applied to RAW and JPEG images before they are stored on its memory card. This is easy to test as I did by doing some raw images with one Param Set turned up to Maximum and another Param Set to Minimum levels. You can see the diffence in the resulting RAW images when you load them (with Linear representation of the image). So I use Param Set 2 because it has all Param Settings set to zero.
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Originally Posted by Itchy
This is why I continually push my Linear barrow. If you want to convert your RAWs to achieve what the sensor recorded, you need to perform a linear conversion. If you convert to normal tiff (or Jpeg), the In-camera processing is going to do the stretching for you. The consequences are, as Paul has pointed out, the calibration will not be accurate. Parameter 2 may apply less processing, but it still mucks things up.
With ordinarly Linear conversion to tiff, the only processing that is applied is the Bayer colour interpolation and some white balance. This is OK, but there is still a better way.
What I now do exclusively is convert my RAW's to no white balance, pre-Bayer CFA (Colour Filter Array). Only after dark, flat and bias calibration are they converted to colour. This is the best way to get to the RAW data from the chip.
Cheers
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Linear conversion is what every astrophotographer uses ( I hope ) so that the intensity of light in the resulting image is directly proportional to the light that fell upon the sensor.
Where you say "If you convert to normal tiff (or Jpeg) the In-camera processing is going to do the stretching for you", again I do not agree with this. If you convert to Tiff/Jpeg then it is the image processing that does the stretching for you (not the camera).
In fact the camera will not stretch a histogram (even with JPEG images), instead it applies a Logarithmic stretch to the intensity of light that fell upon the sensor - this has the effect of "livening up" dull areas of a normal daylight image.
Anyhow, it's all fun and games eh?
Paul