Do not interpret OlympusEq.LensType 0 0 0 0 0 0

[sarunasb]

Olympus/OMDS cameras use '0 0 0 0 0 0' LensType, when mechanical lense is used. Currently Exiv2 interprets this into localised string ‘None’. However Olympus cameras traditionally allow to enter a custom string for lens name and then add that to Exif LensModel of images taken. Image processing software can take None from the LensType and ignore LensModel. Having LensType of '0 0 0 0 0 0' would allow for an easy if statement and then use LensModel instead.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.62%. Comparing base (77915ad) to head (eccf82c).
Report is 41 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3036      +/-   ##
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- Coverage   64.62%   64.62%   -0.01%     
==========================================
  Files         104      104              
  Lines       22239    22253      +14     
  Branches    10911    10923      +12     
==========================================
+ Hits        14371    14380       +9     
- Misses       5626     5628       +2     
- Partials     2242     2245       +3     

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[kmilos]

Image processing software can take None from the LensType and ignore LensModel. Having LensType of '0 0 0 0 0 0' would allow for an easy if statement and then use LensModel instead.

Any clients are also free/should compare if the uninterpreted LensType value is {0,0,0,0,0,0} as the translated string can indeed be localized. Both the lib API and the CLI tool already let you get the uninterpreted value, so not convinced this is absolutely necessary...

Also note that the current behavior is consistent w/ exiftool: https://exiftool.org/TagNames/Olympus.html#LensType

[sarunasb]

Any clients are also free/should compare if the uninterpreted LensType value

Is that possible, when using API? (#3019)

[kmilos]

Is that possible, when using API?

value.toString() just a few lines above does exactly that. Works the same on Exifdatum object corresponding to the desired key (just passes to its internal value_->toString()):

exiv2/src/exif.cpp

Lines 336 to 338 in 44bc543

	std::string Exifdatum::toString() const {
	return value_ ? value_->toString() : "";
	}

Only Exifdatum::write() calls through the special "pretty printer" functions that do the interpretation/translation.

[sarunasb]

Thanks for answering re. API.

I still don't think translating 0 lenstype to localised word is worth it. Especially in case of Olympus, where lensmodel can have lens name even with lenstype remaining 0, but appearing as None… ;)