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Unlike an SLR, it is not possible to remove the lens from compact digital cameras or camcorders. This means that you cannot use eyepiece projection when connecting to a microscope or telescope. Camera attachments for microscopes and telescopes designed for use with an SLR are unlikely to be suitable for use with digital compacts or camcorders. A different technique to eyepiece projection is required, and you have to adopt a procedure known as a-focal photography, whereby the lens of the camera has to be positioned as close as possible to the instrument eyepiece. This requirement may well preclude the mounting of a digital camera/camcorder on a microscope trinocular head or camera port, unless the internal optics or eyepiece are at the end and easily accessible. With a-focal photography, it is quite likely that the image will suffer from vignetting, and will be circular in shape. This can be minimised by choosing a low power, wide field eyepiece. You are having to photograph through the exit pupil of the eyepiece, and this can be very small in diameter. If the camera has a zoom lens, this can be used to minimise the vignetting, but in doing so, the image becomes magnified. Very good results can be obtained in this way, but particular attention must be paid if viewable field width and magnification have any relevance to the results. As the resultant image may vary dramatically from that through any other visual eyepiece in the system, it is important that all the work is done through the camera. At the very least, you will need to use the LCD screen on the camera, or better still, if the camera has a live video output, you can work directly from an external monitor. Camcorders should connect to an external monitor with no problem.
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