Fimagena / raw2dng

Linux utility for converting raw photo files into DNG, TIFF or JPEG format
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Baseline values for Canon EOS 5D Mark III #8

Open Fincer opened 7 years ago

Fincer commented 7 years ago

As I'm an owner of the camera model mentioned in the title and noticed that raw2dng don't add correct values for the following tags...

...I decided to get correct values for each ISO setting for this camera model with the Windows GUI version of Adobe DNG Converter.

I analyzed converted DNG files with exiftool, and added required code to raw2dng so it writes exact same values for these tags (5D Mk3) as the Adobe's "official" software. I have merged the commit to my fork of raw2dng repository found here: https://github.com/Fincer/raw2dng

If anyone is interested, values for these tags, according to my tests & Adobe DNG converter, are as follows:

Camera Model: Canon EOS 5D Mark III

ISO Value                Baseline Exposure Value

ISO 100                  0.25
ISO 125                  0.25
ISO 200                  0.25
ISO 250                  0.25
ISO 400                  0.25
ISO 500                  0.25
ISO 800                  0.25
ISO 1000                 0.25
ISO 1600                 0.25
ISO 2000                 0.25
ISO 3200                 0.25
ISO 4000                 0.25
ISO 6400                 0.25
ISO 8000                 0.25
ISO 12800                0.25
ISO 16000                0.25
ISO 25600                0.25

ISO 50                  -0.75     (yes, you read it right)
ISO 160                  0.02
ISO 320                  0.01
ISO 640                  0.01
ISO 1250                 0.01
ISO 2500                 0.01
ISO 5000                 0.01
ISO 10000                0.01
ISO 20000                0.01
ISO 51200                0.36
ISO 102400               0.36

The following EXIF values are same for all ISOs:

Baseline Noise           0.8
Baseline Sharpness       1.2
Bayer Green Split        100

The only negative side effect I noticed is that Max Aperture Value and Firmware tags are missing, contrary to the original raw2dng software. However, this should not be a big issue because the information included in these tags has been written into Max Aperture, Firmware Version tags, respectively. Value for Image Number tag is still missing, but I don't think it's a big issue either. At least it returned only 0 for the test image I used for the Exif tag comparison analysis of patched vs unpatched (original) raw2dng.

Commit:

Fincer@9616dcec1ecafbd4437dce357c398dd4382446fb

About the meaning of Baseline Exposure in RAW file processing using Adobe Camera RAW/Lightroom software:

http://www.martinzimelka.com/homepage/Blog/Entries/2016/12/25_Subtract_Adobe_Camera_RAW_Baseline_Settings.html

https://photographylife.com/adobes-silent-exposure-compensation

Fimagena commented 7 years ago

Great - thanks for doing this! Would want to integrate but the patch needs some more work:

A while ago, I automated the tag-comparison between Adobe/raw2dng for many cameras but haven't gotten around to publish the code yet. The summarised output is here - as you can see, there are more 5DIII-tags that are inconsistent than the ones you mention.

Do you feel like writing a full CanonProcessor and potentially adjusting additional tags/cameras as you go along? (although, we shouldn't automatically assume that Adobe output is 'right')

Fincer commented 7 years ago

No problem, it's good to help a project like this one.

Thanks for pointing out those issues, makes more sense now. I may check/repair the code some day but for the meantime, the program returns all values I need for my photo processing workflow. Baseline values were the ones I was after, and I noticed that raw2dng didn't return values used by Adobe DNG Converter for 5D Mark 3. Surely I miss some values now but I'm still satisfied enough.

If I decide to implement CanonProcessor someday, I'll surely address and take a look on the issues you mentioned.

I agree we shouldn't assume Adobe's values are correct but that's the best reference we have. I lack equipment to measure correct values (field test) for Canon EOS 5D Mark 3.

P.S. Thanks for creating that sheet by the way! It contains surely valuable information for further implementations. Please keep it available.


For anyone who is interested to actually measure Baseline values for any camera model, take a look into this webpage:

https://www.rawdigger.com/howtouse/deriving-hidden-ble-compensation

Extra info for Canon 5D Mark III + Adobe Camera Raw users

Baseline Exposure offset values used in default camera profiles in ACR for Canon EOS 5D Mark III are as follows:

Exposure offset for all Canon EOS 5D Mark III profiles (Standard, Neutral, Landscape etc.): 
-0.25

Exposure offset for Adobe Standard Profile (Canon EOS 5D Mark III): 
0.00

These Camera Profile values are not visible in normal processing workflow in ACR but it's still good to be aware of them.