Unscrewed rear cells for 4 full turns and then refocused
F4.5
F11
The "Cooke" Portrait Lens.
THE "Cooke" lenses, manufactured by Cooke/Taylor, Taylor & Hobson are well known for their efficiency. Series II Cooke lenses combine the advantages of the modern anastigmat-flatness of field and freedom from anastigmat at full aperture---with an adjustment enabling the photographer to introduce at will spherical aberration evenly over the whole plate. By unscrewing the back lens exactly three turns, the maximum definition is obtained. The lenses work at F4.5 and are designed more especially for the use of professional photographers.
