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Selection of Components

A complete system consists of a lens, an adjusting helical focus mount, a camera adapter and possibly one or more extension tubes.

As a rule, the magnification ß’, defined as the negative ratio of image size to object size, and the object-to-image distance OO’, the distance between the object and the sensor/film, are specified by the imaging task. Consult this chart for more information.

For enlarged images (ß’=-1...-5) it is recommended that the lens is used in its reversed position; that is with the front mounted toward the camera. Please keep this chart in mind.

Based on these charts, a lens can be selected that has a suitable object-to-image distance for the required magnification. The flange-to-image distance (the distance of the mounting surface of the lens from the sensor/film) needed for selecting required extension tubes, is obtained by extending a perpendicular line upward on the current image scale and reading the value on the measurement line of the selected lens.

This value is made up of the flange-to-image distance of the camera (the distance of the sensor/film from the mounting surface of the camera) and the individual lengths of the camera adapter, helical mount and any possibly needed extension tubes. In order to have reserve focus adjustment available, the calculation should start out from a helical mount in mid position (23.4 mm with +/-6 mm of focus travel).

The length of the extension tube is therefore obtained by deducting the known flange-to-image distance of the camera, the length of the adapter, and the average length of the helical mount from the flange-to-image distance.

Contact an optical engineer for help designing your system.

Download the Macro System Brochure.