USB数码相机（ USB cameras） are often offered as eyepiece cameras (video eyepieces) or with a C-mount connection. The components and quality vary greatly between different manufacturers, but all of them have _disibledevent= 2240 Mbit/second

USB 2.0 cameras with resolutions of up to 10 megapixels only provide a data transfer rate of 480 Mbit/second.

Interface  Data transfer rate 
USB1  12 Mbit/second 
USB2  480 Mbit/second 
USB3 (not yet on the market)  5000 Mbit/second 
HDMI 1.2  3960 Mbit/second 
DVI  3700 Mbit/second
The greatly reduced image reproduction rate under 10 images per second poses a problem when focussing the microscopic images.

A strong time lag makes the choice of the optimum focal plane more difficult. If a lower resolution is selected, the focal plane is more difficult to find.

Conclusion: For professional use in microscopy, we can only recommend USB cameras with reservations. However, with a little patience and intuition, good results can be achieved. The new digital HD SLR cameras, such as Canon’s EOS 5D II with “Live View” and HDMI output, offer an alternative to expensive HD video cameras. In video mode, these cameras deliver a real time preview in HD (high definition) quality via the HDMI output. The large format sensor chip of digital SLR cameras has an excellent signal to noise ratio and a photo resolution of over 20 megapixels.