Dallmeyer AM 14" f/5.6

During the two world wars lens makers were contracted by the Air Ministry to make lenses for aerial surveillance.  Air Ministry lenses are invariably painted black and have a little arrow symbol and/or the letters AM stamped on them.  They rarely carry the manufacturer’s name, but the serial number has code letters added.  In this case they’re UU, recognised as the Dallmeyer prefix, one of the finest makers of the era. The remains of an imprint, JHD, are also just visible on the barrel.  

This is a 14″ f/5.6 lens of unknown design, but possibly a “Serrac” type, a very well-regarded formula of the inter-war years.  It’s in typical AM condition – a bit battered on the outside, but the glass is pretty clear.  AM lenses tend to be cheaper than shiny brass civilian copies because they’re not as pretty, but optically the ministry demanded top quality.  Sharpness was a critical factor in getting high resolution aerial photographs.  14″ is around a 52mm equivalent focal length, a versatile standard lens, ideal for portraiture.  An open aperture of f/5.6 is the goldilocks zone for large format lenses, wide enough to be nice and bright on your glass screen, but not excessively large and heavy.  In use it’s sharp wide open, with a hint of softness, but stopped down it sharpens up and the contrast improves.  The bokeh is a little edgy, even bubbly, definitely not as smooth as some, but all in all it’s a fine and useful lens for very little money.  It has an integral mounting flange and is attached to a simple behind-the-lens shutter block.