With my echo program, we were in class for 3 days a week and internship days were varied.
I believe it depends on the site, the lab setting and techs. Some labs only want you to observe. While others it is up to the preceptor to show you what is going on.
At my first internship, I was observing at first, then after a couple weeks, The tech would do the study and then ask the patient if I could take a few more pictures. With in a month, I was scanning and having someone checking my work or they would come to see where I was at in the study.
As I said with lab setting, it depends on the patients. Some settings are more sensitive.. an example is pediatrics. When I did my peds internship, I didnt do as much scanning as the families/patients were more anxious.
Even in some adult lab settings, some people want the study to be done fast and if they know you are student, they will be disgruntled the whole time.