0% MTF corresponds to zero contrast and means that a transition from 100% intensity to 0% intensity – white to black – will be rendered as 50% gray and it will be impossible to tell the two apart. This formula will return the spatial frequency in cycles per millimeter (lp/mm) at which the MTF is 0%. Where λ is the wavelength of light in µm. Of course as you will see below a bigger aperture grows some aberrations so there is a “competition” at play the winner of which will be determined by the skill of the designer and constraints placed on the design. This limit is known as the diffraction limit, and it may be calculated in terms of the modulation transfer function via the formula below. The lower the f number, the higher the resolution limit becomes. The only limitation in a “perfectly” corrected system is how fast it is - the maximum possible resolution of a lens is determined by its f number. If a lens is “perfectly” corrected for all aberrations and has even transmission across the entire spectrum of interest, it is completely “transparent” and will impart no character to the image. All of these things stem from imperfections (aberrations) within the optical system. Photographers will get into great debates about lens character, lens rendering and a whole host of other points of discussion. Brandon Dube for under exclusive licenseĬamera lenses are wonderfully imperfect devices.
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