Many photographers have bought two lenses and one shutter with the idea of extending the focal length range. Two 19" ( 476 mm ) elements make a symmetrical lens of 273 mm, and two 25 1/2" ( 646 mm ) elements make a 368 mm lens. The sequence is 273mm/10.75" f.5.6, 311, 368mm/14.5" f/8, 476 f/11, and 646 mm f/16. These focal lengths cover 8x10 inch format with generous movements. This lens was not designed for 11x14 inch format, so the shortest focal length may vignette, but all the rest cover.

DESCRIPTION

The COOKE XVa is a lens made in small quantities, to very high standards, with multicoated surfaces and full COLOR CORRECTION. It makes a brilliant image for color or B&W films and digital backs. The use of high refractive index lanthanum glass in two of the elements allows better corrections and flatter lens surfaces. This also makes the quality of the image from single elements about five times as good as the original series XV. There is no need for yellow filters, minus blue, to sharpen the image in black and white. It projects a sharp, high resolution, high contrast image at f/6.8 on 8 x10 inch film. The individual elements are f/11 and f/16 and they too project a sharp color corrected image on 8x10 inch format film. The Copal No3 shutter fits on a 4" Linhof Technika type lens board. S.K.Grimes makes some very nice inner lens caps, very useful when one element is removed from the shutter.