THE FIRST CONVERTIBLE LENS TO BE OFFERED IN MODERN TIMES It is now possible to buy a fine modern convertible lens set. On a par with and following the tradition which started with the famous Protar made by Carl Zeiss, the Wisner Plasmat is a series of convertible lens sets which may be used in combination or singly to form different focal lengths of wide-field double- or long focus single-cell lenses. These "Convertible Plasmats" are grouped into four sets, complete with shutter and cell case and engraved brass table of f:stops. Each set is suitable for the standard formats of 4x5 (focal lengths of 152mm to 450), 5x7 (182mm to 500mm) and 8x10 (227mm to 600mm) and consists of five, five or four cells, respectively. Each set is capable of forming eight or more practical focal lengths in their respective ranges, resulting from the combination or single use of the various cells in each set, affording considerable savings in weight and expense.

 An example what can be done if you have patience and perseverance...

(If you don't mind to burn a few polaroid sheets :-) ) 

"Thijske" , my MainCoon by JD on Polaroid type 54 , Linhof Super Technika V.

Driebergen- The Netherlands