Why is there such lag in USB microscope camera?

I bought a microscope camera from AMScope like the one here Here is the specs of the mac I use it with:
2.3 GHz Intel Core i7
16 GB 1600 MHz DDR3
Intel HD Graphics 4000 1024 MB

I was hoping the feed from the camera would be live, but there is enough lag in that it makes it a pain to use. I use the microscope to identify aquatic insects, and it requires quite a bit of manipulation (using small picks, forceps to move around specimens) and also adjusting the focus. I bought it so I could not only take photos of specimens, but also use a large monitor to view through the scope instead of my face at the eye pieces. The lag in the feed however slows me down to the point where it is not very useful. I wanted to figure out if the lag is due to the camera itself (it wasn't top quality) or if it's my computer's hardware that's slowing the feed. The camera's specs show it has 15fps at the highest resolution, which is what I thought the cause was. If so, what would be a good fps for a new camera that would give a good, fast, live feed?

 

Your application is different but I have noticed some games with the frame rate displayed that @ 15-20 fps your mouse moves faster than the screen reacts, and about @ 25-30 motion is continious, more smooth. 10 more fps could be noticable.

 

Could it be that the time is required to build up enough of a picture ? Can this be controlled by the software supplied ? (ie it may take the time to build up an image on the CCD rather than it being an issue with transmitting the data or you computer)

I have always understood the human/brain cannot respond faster than ~25Hz, so 15fps could seem a bit laggy. I have believed that this was the reason that (older) TVs operate @ 50-60Hz picture rep rate (well, 25-30Hz if you count alternate linescan). Search for 'eye response time' on the internet - it seems to subjective/depend on the individual

I bought a cheap USB microscope x50 - x500 and there didn't seem to be any lag problem, but I haven't used it much. I can control the illumination level though (not remotely)

What's the minimum magnification (if it makes any sense to ask that) and what is the field of view at that magnification ? My device gives me less than about 5mm @ "x50"

Dumb_Question
18.October.2014