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 4 2-6-0 76084 safety technologies - TPWS Mark IV, OTMR, and GSM-R - were fitted and tested after raising a further £100,000 from shareholders and supporters. The engine worked its first charter train on Sat 25th February 2017, the tour being The Railway Touring Company's "Buxton Spa Express" which she double headed with 45690 Leander. BR Standard Class 4 2-6-0 76084 BR Standard Class 4 2-6-0 76084 is a BR Standard Class 4 2-6-0 locomotive built at Horwich in March 1957. Owned by "The 76084 Locomotive Company Limited" she is one of only four surviving members of her class in preservation. 76084 was