Doug Kerr
Well-known member
The Exif file specification provides for three "subsecond" timing tags, one for each of the basic timing values: file modified date/time, image capture date/time, and image digitized date/time.
According to the specification, the subsecond timing value is to be interpreted as decimal digits in the seconds value of the time. Thus, if one of the date/ time tags shows:
and the corresponding subsecond tag shows 17, the date/time is:
If the date/time tag shows:
and the corresponding subsecond tag shows 170, the date/time is:
(the same time, actually, to the second decimal place).
Now, as I examine the Exif metadata for my EOS 40D files, I find that the preponderance of them show "00" for the three subsection values. (I would expect them to be uniformly distributed between 00 and 99.)
But a few have other values. I have in fact seen a 99.
Now, when I recently fired some a sequences of shots, I find that the subsecond tags typically are 00 for teh first shot in the burst and then advance by perhaps 15 to 17 from shot to shot (0.15 to 0.17 sec). These seem reasonable considering that the rated maximum burst speed of that body is 6.5 fr/s, which would be an increment of 0.153 sec (15 units in the subsecond tags).
But when I fire single shots, the preponderance give subsecond tags of 00. But not all.
Do we know what this means?
Perhaps the subsecond clock does not run all the time - only once a burst begins. After all, its only real significance is probably in connection with bursts of frames - sorting out in what sequence they were taken (if the filename somehow does not tell us that, or is not accessible).
Best regards,
Doug
According to the specification, the subsecond timing value is to be interpreted as decimal digits in the seconds value of the time. Thus, if one of the date/ time tags shows:
2011.06.04 21:52:26
and the corresponding subsecond tag shows 17, the date/time is:
2011.06.04 21:52:26.17
If the date/time tag shows:
2011.06.04 21:52:26
and the corresponding subsecond tag shows 170, the date/time is:
2011.06.04 21:52:26.170
(the same time, actually, to the second decimal place).
Now, as I examine the Exif metadata for my EOS 40D files, I find that the preponderance of them show "00" for the three subsection values. (I would expect them to be uniformly distributed between 00 and 99.)
But a few have other values. I have in fact seen a 99.
Now, when I recently fired some a sequences of shots, I find that the subsecond tags typically are 00 for teh first shot in the burst and then advance by perhaps 15 to 17 from shot to shot (0.15 to 0.17 sec). These seem reasonable considering that the rated maximum burst speed of that body is 6.5 fr/s, which would be an increment of 0.153 sec (15 units in the subsecond tags).
But when I fire single shots, the preponderance give subsecond tags of 00. But not all.
Do we know what this means?
Perhaps the subsecond clock does not run all the time - only once a burst begins. After all, its only real significance is probably in connection with bursts of frames - sorting out in what sequence they were taken (if the filename somehow does not tell us that, or is not accessible).
Best regards,
Doug