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
Dancing on Ice (series 6) compete in the skate-off as usual, but their fellow celebrities deciding which of them would stay in the competition instead of the judges. On 6 March, the six remaining celebrities took part in the first ever team challenge. Following their standard performances, they were divided into two groups of three, with each group performing their own routine. The judges then decided which performance was best, with every celebrity in the winning team having their previous scores doubled. Two weeks later, on 20 March, the four remaining celebrities performed a solo routine following their standard performances. The final, on 27 March,