Accurate timing with DSLR cameras. Recorded time in the RAW file.

[han59]

Several programs can read the observation time from DSLR raw files. For example Pixel Insight, Siril and the latest ASTAP can convert the RAW file to FITS and report the time of observation behind the keyword DATE-OBS. Something like this:

DATE-OBS= '2016-12-31T19:36:38.000' / [UTC] The start time of the exposure  

The time behind DATE-OBS is normally the start time of the exposure as recommend by the FITS 4.0 standard. While implementing this in ASTAP, I have doubt this is always true for the time extracted from a RAW file (exif info). I got one report this is true for one camera producing CR2 raw files. But raw files made with my S7 smartphone the recorded time is the end time of the exposure. I like to check this for other DSLR cameras and I'm looking for help by DSLR camera owners to test this.  Testing is in principle easy. Set the time correct in your camera, make a long exposure like a dark and manually record the start time. Then check if the reported time in the RAW is at the beginning of the end of exposure. Or if the file date is correct compare it with the file date. Feedback on this topic is most appreciated.

Han

 

 

Edited November 25, 2022 by han59