Extension ring
In the case of small objects, the working distance is often shorter than the minimum object distance (MOD) of the selected lens.
To be able to focus the lens nevertheless, the minimum object distance has to be reduced. This can be achieved by putting one or more extension rings between lens and USB camera, FireWire camera or GigE camera. The Imaging Source offers a low-priced set of extension rings and tubes for this purpose.
In contrast to a common belief, extension rings do not increase or decrease the depth of field of the lens. However, it is true that the image quality suffers, if the extension rings (or better tubes) are very long. In the vast majority of applications, however, only rings of 0.5 and 1 mm are used. They do not have a negative impact on the image quality.
