: Tim Corio wrote: : : > How are "resolving figures" represented? Is there some standard unit of : > measure for sharpness? I've heard of circle of confusion, but was : > confused by it. Perhaps I need to take the time to understand it. From: "ADavidhazy" : The "sharpness" of lenses is expressed in many different ways but a common way : is to characterize them by line pairs per millimetre at the image. ... <clip>.. : Depth of field is usually not connected with lens sharpness. Additional thoughts about other factors affecting sharpness: Motion of the camera during exposure. Motion of the shutter (focal plane being the worst) Diffraction caused by the shutter (focal plane again being the worst) - using flash can overcome this. Diffraction caused by the iris - shooting at the 'optimum' aperture can overcome this. Shooting wide open (generally) Lens flare lowering contrast, therefore sharpness. - cheap fix with a lens hood. The cine guys (who's exposures are generally viewed REALLY big know the benefit of a compendium lens hood which blocks ALL but the image forming light. A dirty front element. This causes flare thus lowered contrast thus lower sharpness. Unnecessary filters. Additional internal reflections causing lowered contrast >lower sharpness. k
