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Adding a new lens

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Luis Díaz Más edited this page Feb 9, 2022 · 8 revisions

  1. Before changing the C++ code to recognise a lens, please consider using the Configuration File as documented in the man page: https://exiv2.org/manpage.html

  2. The code required to recognise a new lens is different for each manufacturer. I've documented the approach for Nikon lenses below. If you update the procedure for another manufacturers, please let me know and I will update this wiki page.

  3. We will not accept a change to the C++ code without a test image. The procedure to create a test file is documented here: Creating a test file

  4. Add a python script to test your change using your test image. Here's an example from a user: https://github.com/Exiv2/exiv2/issues/1368.. I explained the test harness to him here: https://github.com/Exiv2/exiv2/issues/1368#issuecomment-711407187

  5. Run the test suite before submitting your PR. This is documented in README.md.

Adding a new Nikon Lens

The code for nikon lens's is in src/nikonmn_int.cpp:

// lid:   LensIDNumber
// stps:  LensFStops
// focs:  MinFocalLength
// focl:  MaxFocalLength
// aps:   MaxApertureAtMinFocal
// apl:   MaxApertureAtMaxFocal
// lfw:   MCUVersion
// ltype: LensType
// The tcinfo, dblid and mid fields are being ignored.
static const struct FMntLens {unsigned char lid,stps,focs,focl,aps,apl,lfw, ltype, tcinfo, dblid, mid; const char *manuf, *lnumber, *lensname;}
fmountlens[] = {
....
// https://github.com/Exiv2/exiv2/issues/743
{0xc9,0x48,0x37,0x5c,0x24,0x24,0x4b,0x4e,0x01,0x00,0x00, "Sigma", "", "24-70mm F2.8 DG OS HSM Art"},
//  https://github.com/Exiv2/exiv2/issues/598 , https://github.com/Exiv2/exiv2/pull/891
{0xCF,0x47,0x5C,0x8E,0x31,0x3D,0xDF,0x0E,0x00,0x00,0x00, "Tamron", "A030", "SP 70-300mm F/4-5.6 Di VC USD"},
//
{0xf4,0x4c,0x7c,0x7c,0x2c,0x2c,0x4b,0x02,0x00,0x00,0x00, "Sigma", "", "APO Macro 180mm F3.5 EX DG HSM"},
// https://github.com/Exiv2/exiv2/issues/1078
{0x80,0x48,0x1C,0x29,0x24,0x24,0x7A,0x06,0x00,0x00,0x00, "Tokina", "", "atx-i 11-16mm F2.8 CF"},
// https://github.com/Exiv2/exiv2/issues/1069
{0xc8,0x54,0x44,0x44,0x0d,0x0d,0xdf,0x46,0x00,0x00,0x00, "Tamron", "F045", "SP 35mm f/1.4 Di USD"},
// https://github.com/Exiv2/exiv2/pull/1105
{0xCB,0x3C,0x2B,0x44,0x24,0x31,0xDF,0x46,0x00,0x00,0x00, "Tamron", "A037", "17-35mm F/2.8-4 Di OSD"},
// https://github.com/Exiv2/exiv2/issues/1208
{0xC8,0x54,0x62,0x62,0x0C,0x0C,0x4B,0x46,0x00,0x00,0x00, "Sigma", "321550", "85mm F1.4 DG HSM | A"},
// Always leave this at the end!
{0,0,0,0,0,0,0,0,0,0,0, NULL, NULL, NULL}
};

There are 11 metadata items/lens that must match your lens. You can obtain those values from a photo taken with the lens of interest. This is discussed in the issues referenced in the code. We also require a (simple) python test file when we update C++ lens recognition code.

Please note that all fields except LensType have to be looked up in the Exif.NikonLd* prefix and not other Exif.Nikon* prefixes. For example: for modern Nikon bodies with modern lenses, there will be both a Exif.Nikon3.LensFStops and a Exif.NikonLd3.LensFStops entry in the EXIF data. You are looking for Exif.NikonLd3.LensFStops-

In most cases the necessary hex values should be extracted from a test image using the following command:

exiv2 -ph -g NikonLd3.LensIDNumber -g NikonLd3.LensFStops -g NikonLd3.MinFocalLength -g NikonLd3.MaxFocalLength -g NikonLd3.MaxApertureAtMinFocal -g NikonLd3.MaxApertureAtMaxFocal -g NikonLd3.MCUVersion -g Nikon3.LensType test.NEF

Summary of new lens PR

Here is a typical python test. See https://github.com/Exiv2/exiv2/pull/992. The user provided a test python file tests/bugfixes/github/test_pr_992.py

# -*- coding: utf-8 -*-

import system_tests

class NikonSigmaLens_APO_MACRO_180_F35_EX_DG_HSM(metaclass=system_tests.CaseMeta):
    url = "https://github.com/Exiv2/exiv2/pull/992"
    
    filename = "$data_path/Sigma_APO_MACRO_180_F3.5_EX_DG_HSM.exv"
    commands = ["$exiv2 -pa --grep lensid/i $filename"]
    stderr = [""]
    stdout = [""
        """Exif.NikonLd3.LensIDNumber                   Byte        1  Sigma APO Macro 180mm F3.5 EX DG HSM
"""
]
    retval = [0]

The test file is test/data/Sigma_APO_MACRO_180_F3.5_EX_DG_HSM.exv. The tests executes the program exiv2 -pa --grep lensid/i foo.exv and compares the output to stdout. That's it.

In this case, there is only one exiv2 command being executed on a single file. Most tests are more involved. You'll notice that the variables: commands, stderr, stdout and retval are arrays to make it easy to execute several commands in a single test. The most common program to run is exiv2, however other programs from build/bin or system commands can be invoked. You may not pipe data between commands, however you can redefine the stdin/stdout filter decode_output if required.

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