From simple lens to complete system
A how-to of perfect combinations 

The flange-to-image distance, i.e. the distance between the contact surface of the lens and the camera flange, required for the selection of the extension tubes and the helical mount, can be calculated as follows: In the table in the attached data sheet the fl ange-to-image distance for infinity is named, to which the displacement for the magnification factor is also added. The displacement is calculated as focal length multiplied by magnification factor. If, for example, a lens with 40 mm focal length at a magnification factor of 0.1X is to be used, the displacement from infinity is 40 x 0.1 mm = 4 mm.

The flange-to-image distance (distance between lens and camera) consists of the flange-to-image distance of the camera (distance of the sensor to the attachment surface of the lens) and the total length of the camera adapter, helical mount and any necessary extension tubes. In order to have adjustment reserves in both directions, the calculation should assume a mean length of the helical mount. This is, for example, 23.4 mm for the UNIFOC 12. The length of the extension tubes is determined by subtracting the known quantities flange-to-image distance of the camera, length of the adapter and the mean length of helical mount extension from the flange-to- image distance.

Differences between a V-Mount and a thread
Due to the 360° circumference V-groove a lens with a V-Mount connection can be fixed securely and quickly in any position using set screws. This also makes it simple to align the best azimuth position, which is marked for the lenses for line scan applications, with regard to the sensor. With a thread, on the other hand, it is practically impossible to set the best azimuth position due to the thread cut and the defi ned pitch.

Special aperture setting characteristics
As the starting apertures of the individual macro lenses with V-mount differ, the aperture ring of the lenses uniformly carries the numbers 1 to 6. In position 1 the aperture is fully opened. With each further number the aperture is closed by one f-stop. Half f-stops are indicated by a dot. 

Conversion to the reverse focus position
To switch from normal to retro position, an adapter is required which is screwed into the filter thread of the lens.

V38-System