Canon EOS 40D RAW CR2 loss of dynamic

[georg.viehoever]

Hello,

I have a Canon EOS 40D. Trying to load its RAW files into Pixinsight, I see the following problems: (Converter Settings used: VNG (smooth gradiants) and "Interpolate as 4 colors" (otherwise small artefacts visible))

- with default white balance settings of the RAW Loader, all images have a red base color - even in regions that should be black
- Use of "Camera White balance" in the Format Explorer does not help
- Use "Auto White Balance" does help, but everything is grey, even in regions that should be black.

I compared this to the results when I using Canon's Digital Professional to convert it to 16bit TIFF (linear contrast, no change to histogram), and then reading the result into Pixinsight:

- black is black (and not read)
- image appears to be even smoother
- visually, there is much more dynamic range, especially in the very bright parts of the picture.
- I tried to substatiate this observation by using the dynamic range script posted earlier in this forum. The results partially support the loss of dynamic range, but certainly not to the extent observed visually. See below.

Any ideas what is going wrong here?

Thanks,
Georg


Reading 1 file(s):
C:/Users/Georg/Pictures/2007_12_24/IMG_0371.TIF
Reading TIFF: 16-bit integers, 3 channel(s), 3888x2592 pixels, chunky: 100%

run -x=auto C:/Users/Georg/Pictures/2007_12_24/dynamic.js

Processing script file: C:/Users/Georg/Pictures/2007_12_24/dynamic.js
Calculating effective dynamic range...
IMG_0371
Channel |   Values |  Bits |
--------|----------|-------|
    0   |    15423 | 13.91 |
    1   |    14479 | 13.82 |
    2   |    15927 | 13.96 |


Reading 1 file(s):
C:/Users/Georg/Pictures/2007_12_24/IMG_0371.CR2
Decoding Canon EOS 40D file (3944x2622 pixels, ISO=800, Exposure=1/64s): 100%
Loading raw image: 100%

run -x=auto C:/Users/Georg/Pictures/2007_12_24/dynamic.js

Processing script file: C:/Users/Georg/Pictures/2007_12_24/dynamic.js
Calculating effective dynamic range...
IMG_03711
Channel |   Values |  Bits |
--------|----------|-------|
    0   |    10941 | 13.42 |
    1   |    14118 | 13.79 |
    2   |    10282 | 13.33 |

[Juan Conejero]

Hi Georg,

Indeed we have seen this problem before with 40D raw images. I'll try to find a workaround and will post it here ASAP.

Thank you for your patience.

[georg.viehoever]

Juan,

in the meantime, I found this website: http://www.lebsanft.org/blog/?tag=dcraw: It basically states that Canon EOS 40d support has been added in the dcraw version just after the one included in Pixinsight. I dont know if this is the root cause, but maybe....

Georg

[Juan Conejero]

Wow, you are fast!  

Yes, you nailed the problem. I've just finished integrating dcraw 8.81 in the DSLR RAW module. Now 40D raw images load with the correct color balance using the camera white balance. They also load correctly with no white balance at all, at least in all tests I've made.

In general, you'll see that raw images look dark once loaded in PixInsight. Remember that PI's RAW module loads true raw images without applying any transformation, other than the selected interpolation/debayerization (if any) and white balance. The correct levels can be achieved very easily with HistogramTransform. If the raw image doesn't use the whole available dynamic range, usually the correct illumination levels can be set by just moving leftwards the histogram's white point (without clipping any pixel of course; watch the Clipped Pixels Count).

I have already compiled the RAW module for Linux. It's here:

http://pixinsight.com/export/DSLR_RAW-pm32.so-20071226.tar.gz

Just replace the previous file on the bin installation directory. In a while I'll recompile the Windows module. I'll post a note on the Announcements section.

Thank you for you help.