Focal Lenght Extenders
A focal length extender is an optical adapter ring between the (C-) mount of the camera and the C-mount lens. With this Adapter, you are able to increase the focal length of an industrial c-mount lens. As a result with a 2x focal length extender you zoom a factor 2 and with a 4x focal length extender you zoom a factor 4. It’s used for microscopic views on short working distances or looking at small objects at larger working distances.
If you combine a 50mm lens with a 2x focal length extender the new focal length will be 100mm. If you combine a 50mm lens with a 4x focal length extender the new focal length will be 200mm.
Applications where you are looking at microscopic an object with a field of view of 1x1mm and a working distance of 100mm or the inspection of objects with a distance of 3 meters while the field of view is just 100x75mm.
There are a few important remarks you have to keep in mind when using a focal length extender:
- The adapter only works with c-mount lenses, not with M12 lenses
- The maximum supported sensor size is 2/3 inch.
- You cannot combine multiple focal length extenders.
- Some lenses will lose the ability to focus until infinity. The minimum working distance will not change.
- You will lose light intensity. When using a 2x focal length extender you lose 2 aperture stops of light. A F1.4 lens becomes a F2.8 lens. With a 4x focal length extender you lose 4 stops. A F1.4 lens becomes a F5.6 lens.