The Adon is unusual in that it could be used as an attachment fitting in front of an existing prime lens or as a complete telephoto lens. It was intended to make tele-photography available on hand cameras with fixed lenses. It could also be used as a complete lens with the camera lens removed and in this form it proved most popular. The Adon consists of two groups, a positive achromat at the front and a negative group at the back, the separation between the two groups can be varied.

When used as an attachment the separation of the two lens groups is normally set to be equal to the difference in the two focal lengths, in this arrangement incident parallel rays will emerge parallel. The camera will therefore focus at infinity with its normal bellows extension. The magnification (compared to the image produced by the camera's prime lens) when in this set-up is equal to the ratio of focal lengths of the two Adon lens groups.

If the separation is set to be less than the difference in focal lengths i.e. the two lens groups are brought closer together, the Adon will present divergent rays to the camera lens which will produce an enlarged image (larger than when in the normal position) when brought to a focus at a distance greater than the normal bellows extension.

If the separation is greater than the difference in focal lengths, parallel incident rays will emerge convergent. The magnification will then be less than when in the normal position and the focus will be closer to the camera lens.

When used without a prime camera lens the Adon becomes a normal telephoto lens of variable magnification.

The Adon was made in one size for fixed lens cameras of quarter-plate or 4" x 5" size. When used on its own it was capable of covering a 15" x 12" plate. A rack and pinion was provided to alter the separation of the two components.

In 1910 the tube was made shorter and for use the front lens pulled out on an inner tube. The following year the optics were improved. At this time the fixed magnification Large Adon was introduced. In 1926 the tube design was again altered, the rack and pinion being replaced by a helical movement and the lens being given a modern look with a black painted finish. By this time it could not have been a popular lens. This version could be screwed into the front of a Compur shutter. Early models had an iris scaled 1 - 32, later, before 1910, it was scaled 1 - 8.

The rear negative group had a focal length of 2 ¼", the front positive group was 4 ½". A 1" negative component was available giving greater magnification for which an extension tube was needed.

The Junior Adon was for use with fixed lens cameras, it was made in three models:

• No. 1 for the No. 3 F.P.K. with a standard rapid rectilinear lens.
• No.2 for the No. 3A F.P.K. with rapid rectilinear or anastigmat lens.
• No.3 for Cartridge Kodaks and other double extension cameras.