I think I have worked out my problems, but I am in doubt if my solution is founded on the right perception.
I would like to knpw this: if you have a dataset with, amongst others, a couple of images and user changes 1 img, that one is uploaded and saved into the collection using the .Save in code, on the dataset. But what about the other, unchanged, images on the form? Are they uploaded again or not?
I cannot test this, since the other pics, if uploaded again, would visually be the same. And on a normal, stable, connection you could prob. tell by upload time, but here we sometimes have upload speeds that vary from a couple of bytes per sec to 100k.
Could someone please shed some light into this?