Added contrib/fujifilm_dynamic_range documentation

content/lua.scripts.manual/scripts/contrib/fujifilm_dynamic_range.md

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+---
+title: fujifilm_dynamic_range
+id: fujifilm_dynamic_range
+weight: 105
+draft: false
+author: "people"
+---
+
+## Name
+
+fujifilm_dynamic_range.lua - 
+
+## Description
+
+Support for adjusting darktable exposure by Fujifilm raw exposure
+bias. This corrects for a DR100/DR200/DR400 "dynamic range" setting.
+
+Based upon fujifilm_ratings by Ben Mendis
+
+The relevant tag is RawExposureBias \(0x9650\). This appears to
+represent the shift in EV for the chosen DR setting \(whether manual or
+automatic\). Note that even at 100DR \("standard"\) there is an EV shift:
+
+100 DR -> -0.72 EV
+200 DR -> -1.72 EV
+400 DR -> -2.72 EV
+
+The ideal would be to use exiv2 to read this tag, as this is the same
+code which darktable import uses. Unfortunately, exiv2 as of v0.27.3
+can't read this tag. As it is encoded as a 4-byte ratio of two signed
+shorts -- a novel data type -- it will require some attention to fix
+this.
+
+There is an exiv2-readable DevelopmentDynamicRange tag which maps to
+RawExposureBias as above.  DevelopmentDynamicRange is only present
+when tag DynamicRangeSetting \(0x1402\) is Manual/Raw \(0x0001\). When it
+is Auto \(0x0000\), the equivalent data is tag AutoDynamicRange
+\(0x140b\). But exiv2 currently can't read that tag either.
+
+Hence for now this code uses exiftool to read RawExposureBias, as a
+more general solution. As exiftool is approx. 10x slower than exiv2
+\(Perl vs. C++\), this may slow large imports.
+
+These tags have been checked on a Fujifilm X100S and X100V. Other
+cameras may behave in other ways.
+
+## Usage
+
+Start this script from script manager
+
+## Additional Software Required
+
+exiftool (https://www.sno.phy.queensu.ca/~phil/exiftool/)
+
+## Limitations
+
+## Author
+
+Dan Torop <dant@pnym.net>
+
+## Change Log