Ross 15" f3.8 Gauge Projection lens

Background:

The Ross Optical Company lost their will for innovative lens designs by the 1950's producing neither new developments nor keeping up 

with the latest trends.  In some respects, it is unusual to see the Ross Guage Projection lenses from as recent as 1950's being offered.  Pre-war optical advances in physics led to enhanced designs of projection lenses with the guage projection lens gaining specialist attention via research at the National Physical Laboratory.

The Gauge Projection lens was manufactured as a specialist process lens, namely for engineering examination of projected images 

against outlines of standard drawings.  This required a low distortion across the plane of the image and higher speeds for projection 

purposes.   When produced, the British Almanac identifies these specialist lenses as expensive, costing £35.50 for a 2.25 inch lens.  The Vade Mecum lists up to a 300mm Gauge Projection lens.  This sample has an estimated focal length of 15" with a corresponding aperture of f3.8.

Summary:        A very sharp specialist process lens, reproduction <1:5 scale   optimised for studio, portraiture or still lifework.

Features:      

The Ross Projection lens is a considerable weight of glass at over 2kg.  Neutral Density filters can be used via adaptation of a 115mm Sinar filter holder.  Front mounting on a standard is a particular challenge: the proximal aspect of the lens just fits an international Sinar lens panel.

The lens creates a shift of the centre of gravity when focussed using the internal slide mechanism. Viewing image is superlative and bright.

Lens in slide focussing tube (extended) shown with a 35mm film cassette for comparison.

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