Abstract: There is disclosed herein a slide calculator for determination of flash-to-background distance for studio photography when using color filters over the flash. By use of the calculator, known factors, such as lens f-stop, film speed, flash guide number (GN), background density (darkness), desired degree of color (including shades of gray and white) saturation of said background and filter exposure factors can be used to determine the working distance of a background-flash with a color filter over the flash. An electronic flash meter is not required.The calculator includes a front panel with a window-like aperture and a back panel. Two slide members are positioned and movable between the front and back panels. Indicia is provided on the front panel and is generally arranged adjacent the window like aperture. Indicia is also provided on the slide members and is arranged for exposure at the window.

Abstract: The object of the invention is to provide a slide calculator to make the determination of flash-to-subject working distances (WD) easy and accurate for amateur and professional photographers. Light sources other than flash can be used. The calculator uses known factors such as lens f-stop, film speed, light ratio, flash guide number (GN), flash power setting and filter exposure factors to determine working distances even when using multiple flashes simultaneously. The indicia on the slides and the indicia adjacent the appropriate windows on the panels are arranged in a predetermined manner and relationship to each other to permit the desired working distance to be determined accurately. Working distances for several flashes (each flash having a different purpose) can be determined and their affect on each other is compensated for in the calculations. Then the several flashes can be used in combination to achieve a desired lighting effect with correct exposure.