Method and apparatus for determining printing exposure amount
AssigneeFuji Photo Film Co., Ltd.
InventorKenji Suzuki
Life of this patent
Estimating the term…
Abstract
A photographic printer for making a trimming print has a zoom lens whose focal length can be changed in accordance with a trimming magnification. Exposure time is corrected based on a reciprocity law failure correction amount corresponding to the magnification of the zoom lens, whereby a density of the photoprint is corrected as to a change in a reciprocity law failure. According to a preferred embodiment, test prints are made respectively at a plurality of magnifications of the zoom lens. The densities of the finished test print are measured to form reciprocity law failure correction data automatically in the photographic printer so that the measured densities coincide with standard densities.
Claims12
A method for determining a printing exposure amount for making a trimming print at a specified magnification M by changing a focal length of a zoom lens in a photographic printer, said method comprising the following steps:
- calculating an exposure time T for said trimming print by an equation
- T=T.sub.0 .multidot.[f.sup.2 (M).multidot.(1+M.multidot..phi..sub.EN /.phi..sub.EX).sup.2 ]/[f.sup.2 (M.sub.0).multidot.(1+M.sub.0 .multidot..phi..sub.EN /.phi..sub.EX).sup.2 ]
- where T.sub.0 is a reference exposure time corresponding to a reference magnification M.sub.0 of said zoom lens, f(M.sub.0 ) is a lens f-number corresponding to said reference magnification M.sub.0, f(M) is a lens f-number corresponding to said specified magnification M, .phi..sub.EN is a diameter of an entrance pupil of said zoom lens, and .phi..sub.EX is a diameter of an exit pupil of said zoom lens;
- obtaining a reciprocity law failure correction amount corresponding to said exposure time T based on data of a relationship between an exposure time and a reciprocity law failure correction amount of color paper;
- and
- determining said printing exposure amount for an image frame to be printed in said photographic printer based on said obtained reciprocity law failure correction amount.
An apparatus for determining a printing exposure amount for making a trimming print at a specified magnification M by changing a focal length of a zoom lens in a photographic printer, comprising:
- means for calculating an exposure time T for said trimming print according to an equation
- T=T.sub.0 .multidot.[f.sup.2 (M).multidot.(1+M.multidot..phi..sub.EN /.phi..sub.EX).sup.2 ]/[f.sup.2 (M.sub.0).multidot.(1+M.sub.0 .multidot..phi..sub.EN /.phi..sub.EX).sup.2 ]
- where T.sub.0 is a reference exposure time corresponding to a reference exposure time corresponding to a reference magnification M.sub.0 of the zoom lens, f(M.sub.0) is a lens f-number corresponding to said reference magnification M.sub.0, f(M) is a lens f-number corresponding to said specified lens magnification M, .phi..sub.EN is a diameter of an entrance pupil of said zoom lens, and .phi..sub.EX is a diameter of an exit pupil of said lens;
- means for outputting a reciprocity law failure correction amount corresponding to said exposure time T based on data constituting a relationship between an exposure time for said trimming print and a reciprocity law failure correction amount of color paper;
- and
- means for determining said printing exposure amount for an image frame to be printed in said photographic printer based on said outputted reciprocity law failure correction amount.
Dependencies are inferred from the claim text.