F-number lengths. Therefore, reduced–depth-of-field effects will require smaller f-numbers when using small-format cameras than when using larger-format cameras. Image sharpness is related to f/number through two different optical effects: aberration, due to imperfect lens design, and diffraction which is due to the wave nature of light. The blur optimal f-stop varies with the lens design. For modern standard lenses having 6 or 7 elements, the sharpest image is often obtained around 5.6–8, while for older standard lenses having only 4 elements (Tessar formula) stopping to 11 will give the sharpest image. The larger number of elements in modern lenses allow the
BR Standard Class 3 2-6-0 on a project to build a new Standard Class 3 2-6-2T. This class was the last class of steam locomotive on British Railways to remain complete before suffering its first withdrawal. Number 77014 was transferred from Northwich depot on the London Midland Region to Guildford depot on the Southern Region in March 1966; it was withdrawn in July 1967. BR Standard Class 3 2-6-0 The BR Standard Class 3 2-6-0 was a class of mixed traffic steam locomotive designed by Robert Riddles for British Railways. It was essentially a hybrid design, the chassis being closely based on and sharing a