I believe that photo:getFormattedMetadata ("brightnessValue") is the APEX average scene luminance recorded in the EXIF metadata:
According to the EXIF spec:
I don't really understand any of the details.
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Rob Cole wrote:
* brightnessValue: (string) The brightness value (HELP: need an example)
I could use an example too, and/or an explanation.
I suspect brightness value isn't really used by Lightroom any more. This is why the tech writer didn't have an example to include for this field.
I have checked a number of images (NEF, JPEG, DNG) from different camera types using a metadata tagset including the com.adobe.brightnessValue field. Not one of the sample images displayed a value under Lightroom 4. These same images when checked in exiftool had a "Brighness Value" of "Normal".
Opening up LR 2.7 I managed to find one sample image in that catalog with a brightness value. The metadata tagset field com.adobe.brightnessValue displayed a value of 4.96. This seems to align with the doco John managed to find.
I'd suggest ignoring the field. But I will see if the doco can be updated.
Thanks John, and Matt .
In a catalog of 20K photos from perhaps a dozen different cameras, I found just 150 photos with non-empty Brightness Value fields, mostly from my new Sony RX100, which seems to always insert the field. Skimming the values, they appear to range from about -3 to +7.