This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Cooke Lens, Series III. Full aperture F. 6.5. The Series III. lenses are the best for persons desiring all around anastigmats of the very highest grade. They are designed for general photography, landscapes, interiors, street scenes, and for difficult photographs on dull days. For use as wide-angle lenses on relatively large plates they are perfect. They may be focused wide open and afterwards stopped down, without spoiling the image. Briefly, they are universal lenses suitable for all accurate and rapid work requiring uniformly fine definition. Lenses of this series are the best for kodaks. The No. 3 lens can, if specified, be fitted to the No. 3 kodak, the No. 4 lens to the No. 3a, and the No. 6 to the No. 4a kodak.
Cooke Lens, Series IV. Full aperture F. 5.6. The Series IV. lenses are designed for high-speed photography with focal plane shutters; for groups; for difficult photographs in exceptionally poor lights. The definition is perfect throughout THE SIZES OF PLATE SPECIFIED, even with the full aperture of F. 5.6. In that respect the lenses equal those of the Series III. and V., but they cannot be used with such good effect upon plates larger than those for which they are listed.
838. The advantages of a simple construction are fully developed in this series, and result in objectives of greater rapidity and defining power, with a more uniform excellence than has hitherto been possible in lenses having such large aperture.
839. The right choice of a shutter is of vital importance. The Series IV. lenses can be fitted to the ordinary between-lens pattern, if specified, but the highest efficiency in the photography of rapidly moving subjects can be secured only with focal-plane shutters. For protraiture, a suitable studio shutter is best.
Cooke Lens, Series V. Full aperture F. 8. The Series V. lenses are similar to the Series II., except for their smaller apertures and more compact mountings. Optically, the two series are identical and give equal results at similar apertures.
841. Especially suitable are the Series V lenses for copying, enlarging, machine photographing, and for everything demanding miscroscopically fine definition under average conditions of lighting. Success in government departments and astronomical observatories has been largely with lenses of this series.
Cooke Process Lenses. The illustrations in the leading magazines throughout the world are now made with Cooke Process Lenses. The reason is that for such work they give uniformly well defined images, free from distortion, from fog, and other common defects of lenses; while for three-color work they have the unique property of being adjustable so that in final tests color images of equal size are secured.
843. The lens-hood which receives the cap is removable, and a screw-thread receives inter-changeably any prism or mirror suitably mounted and always in the correct position. An iris diaphragm is provided, in front of which is a slot to receive process diaphragms, if necessary. This slot may be closed or opened at pleasure, merely by revolving the inscription tube.