Taylor Hobson Cooke Apotal 14" f9 Process Lens

Of the many Cooke process lenses, the Apotal series included focal lengths most commonly seen between 300mm to 450mm.  These are thought to be a popular post-war Tessar type design offering coverage at 10x8".  Apertures were given from f9 - f16 between focal lengths of 9" to 35"

Features: The Apotal lenses were noted to be brown coated.  Annotation in centimetres rather than inches seem to be associated with dark purple or blue coatings however a transition period may explain the presence of brown coated glass marked in centimetres whose glass generally appears white.   Older lenses are straw yellow to deep brown in colour.    This sample is straw yellow in winter, and clear in summer, mostly likely due to radioactive earth metals in the glass which alter state in the presence of ultraviolet light (UVb).  This can be attributed to the rear grouping of elements, of which at least one possesses mildly radioactive behaviour.

In 12" & 14" versions, a No.4 Acme shutter using a thin ring to adapt the 57mm thread to the shutter's original 59.4/58.7mm is possible.  In use these lenses hold a strong reputation for even illumination and sharpness.   Identical mounting threads front and rear of the lens enables reverse mounting.

There are similar lenses derived from TTH whose design appears identical yet mounted differently.  Cooke Copying Lenses manufactured for Photostat Ltd. and Taylor Hobson Copying Lens manufactured for Kodak also exist in focal lengths which cover whole plate format (e.g. 10.16" Taylor Hobson copying lens.   Klaus Urbons also records that the 10.16" TTH copying lens was first made for the Haloid Model D variable ratio copier.

Summary:  Moderate weight telephoto process lens with excellent performance characteristic of a Tessar lens  for its vintage.

With thanks to Dan Fromm for supplementary data

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Comments, revisions and suggestions welcome.

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Comments, revisions and suggestions welcome.