Phone embeds Sub Sec Time tags (and others) in images arbitrarily?

[balderdash11]

I am conducting metadata testing with a recent Samsung smartphone; my test sample consists of images taken with the main (rear) camera lens in its default shooting mode, which ensures the same lens takes all the images. From what I can tell, the following 14 tags are produced in the ExifTool results for some images:

Flashpix Version
Components Configuration
Scene Type
Custom Rendered
Contrast
Saturation
Sharpness
Offset Time Digitized
SubSecTime
SubSecTimeOriginal
SubSecTimeDigitized
Interoperability Index
Interoperability Version
Orientation (**a second instance of this tag populating**)

Among my test images - either all these tags populate together, or none of them do. I suspect it may have to do with the subset of "Sub Sec Time" tags, which I believe are only embedded in images taken by specific cameras/phones. However, I find it strange that this information would only be embedded intermittently. Are there external factors controllable by a user that could dictate this behavior?

[StarGeek]

This usually wouldn't be controlled by the user, but different apps might write them differently and if the images was edited, a poorly designed app might not copy the data correctly.

And then there are things like WhatsApp which strip away all metadata.  I think images sent through text also get recompressed and lose data.

[balderdash11]

I understand all bets are off when images are processed through different apps, social media, etc. Many will strip metadata or recompress the images, but I am simply observing the metadata for my sample images in their original JPEG format after transferring them onto my Windows desktop via USB cable. 

I suspected that the variations I observed were not a result of user-generated changes, but I am curious what may be influencing this erratic behavior of the camera. Maybe some quirk related to the firmware. I conducted an additional test with an iPhone 13 and unlike the Samsung S22, the iPhone's rear camera consistently produced the Sub Sec Time tags in all the sample images I took.

Thanks for your reply. 

[Phil Harvey]

My guess is that these tags may either be added or deleted if there is an additional processing step in storing the image (eg. if the image is rotated, or some effect is applied).

- Phil

[balderdash11]

Hi Phil - thanks for your thoughts. I actually determined that the phone's orientation has no effect on this, as the Sub Sec Times will populate in images taken with any of the 4 possibilities (Horizontal, Rotate 90 CW, Rotate 180, Rotate 270 CW). Interestingly, I took a series of 18 photos in the same orientation in rapid succession (many taken within the same second), and each one had the Sub Sec Time tags embedded. After this, I took a series of 13 photos in the same orientation in a more deliberate manner, waiting several seconds in between shots - only 10 of the photos had the Sub Sec Times embedded. Strange.