Hi Phil,
This is Panasonic's APEX-System.
Tag 0x1300 is the metered SceneBrightness (Bv)
Tag 0x1301 is the calculated ApertureValue (Av)
Tag 0x1302 is the calculated ShutterSpeedValue (Tv)
Tag 0x1303 is the calculated SensitivityValue (Sv)
all Values sSHORT /256.0f
BV corresponds always to the formula AV+TV-SV.
The formula EV = AV+TV = BV+SV works always fine (with a little compensation ~ -1/6).
The given AV SV TV are corresponding to the resulting FValues ISOs and Speeds given in other sections of Metadata.
There are several patents explaining this system.
One is US-Patent 8558936 B2.
In some newer Cams:
Tag 0x3504 is the result of Tag 0x1301+0x1302-0x1303 (AV+TV-SV)=BV (calculated)
Tag 0x3505 is a copy of 0x1300 (BV measured)
Klaus
Hi Phil,
I'm not sure that BV is correct for Tag 0x1300.
It is the given "Lightlevel of the Scene" measured by the Metering-System.
I think it's called 'incident light' IV? in the APEX-system.
In poor light conditions with activated flash, the value of 0x1300 can be very low,
while the calculated BV from AV+TV-SV can be much higher.
If present, Tag 0x3504 is the correct calculated BV and Tag 0x3505 is a simple copy of 0x1300 IV?.
Klaus
Hi Phil,
Cams like the GX8 have
Tag 0x1306 val/256.0f ==> EV
Newer Cams like G9 have
Tag 0x3504 and Tag 0x3505
They have 0x1306 too but don't use it anymore. Always 0.
Klaus
Hi Klaus,
Thanks. I'll add decoding for some of these to ExifTool 12.02, and add comments for the others.
- Phil