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
Category 6 cable shield, and these currents may in turn induce detrimental noise in the signal being carried by the cable. Soon after the ratification of Cat 6, a number of manufacturers began offering cable labeled as "Category 6e". Their intent was to suggest their offering was an upgrade to the Category 6 standard—presumably naming it after Category 5e, which was a standardized enhancement to Category 5 cable. However, no legitimate Category 6e standard exists, and Cat 6e is not a recognized standard by the Telecommunications Industry Association. Category 7 is an ISO standard, but not a TIA standard. Cat 7 is already