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Support compensation for Canon's Highlight tone priority #21371

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piratenpanda wants to merge 3 commits into from
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Support compensation for Canon's Highlight tone priority #21371

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37c0c0a
Support compensation for Canon's Highlight tone priority
piratenpanda Jun 20, 2026
f5aee45
Move HTP to override position
piratenpanda Jun 21, 2026
09b6c3c
Make HTP additive
piratenpanda Jun 22, 2026
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11 changes: 11 additions & 0 deletions src/common/exif.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1146,6 +1146,17 @@ static void _check_highlight_preservation(Exiv2::ExifData &exifData,
img->exif_highlight_preservation = 0.0f;

Exiv2::ExifData::const_iterator pos;

// Canon Highlight Tone Priority: checked independently of ALO since both tags
// can be set simultaneously on modern Canon bodies.
// D+ (1) and D+2 (2) both apply ~1 EV sensor underexposure; D+2 is scene dependent
// according to Canon but start with 1 EV here as well.
if(FIND_EXIF_TAG("Exif.CanonLiOp.HighlightTonePriority"))
{
const long state = pos->toLong(0);
if(state > 0)
img->exif_highlight_preservation = 1.0f; // D+ or D+2: ~1 EV underexposure
}
if(FIND_EXIF_TAG("Exif.Canon.LightingOpt")) // Active Lighting Optimization
{
// tag consists of an array of long values
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