![]() ![]() The Academy welcomes feedback regarding SSI. We believe this is also applicable to other areas in which quality reproduction rendering or perception of color is important. SSI was later revised to add the ability to use other reference illuminants such as blackbody illuminants of arbitrary color temperature and CIE standard illuminants.)Īdditional general information on solid state lighting and how it affects color rendering can be found on the main SSL page:Ĭinematographers see value in an index that provides a level of confidence in color rendering independent of the camera used. We’ll start by adding a few useful classification metrics to the MNIST example we started with earlier. (Note: In that presentation, the only reference illuminants postulated were ISO daylight and studio tungsten. SSI is fully described in a presentation that was given to the Society of Motion Picture and Television Engineers (SMPTE) at its technical conference in 2016 (accessible by SMPTE and IEEE members at ). Instructions for using the calculator can be found at: SSI has been adopted and published by the Society of Motion Picture and Television Engineers as a SMPTE standard, ST 2122.Īdditional information on basic lighting and color principles, lighting metrics currently used in motion picture production, why SSI was developed, and how it is calculated, is available in this white paper:Ī tool for calculating the SSI is also available: SSI is useful for cinematography, television, still photography, and human vision. High values indicate predictable rendering by most cameras (as well as “quality” of visual appearance) low values may produce good colors with a particular camera but not with others. Rather, it quantitatively compares the spectrum of the test light with that of a desired reference light source, expressing the similarity as a single number on a scale up to 100 (which would indicate a perfect match). The TLCI measures rendering by an idealized three-chip camera, which does not adequately account for the differing spectral sensitivities of single-chip cinema- or still-camera digital sensors.įor these reasons, SSI is not based on human vision, nor any particular real or idealized camera, and does not assume particular spectral sensitivities. Existing color metrics were not designed for cinema cameras CRI, for example, is based on human color sensitivity rather than camera sensitivities. These spectral distributions can wreak havoc with color rendition (by both film and digital sensors), since film and digital cameras are all expressly designed to work with, and are indeed optimized for, standard tungsten and daylight. In contrast to the relatively smooth, broad-spectrum power distributions of blackbody emission, tungsten incandescence, and daylight (and the ISO standardizations of these sources), many solid-state lights are characterized by peaky, multimodal, or narrow-band spectral distributions. Lightning This is a non-interactive table because there are no stats to be input. The Spectral Similarity Index, or SSI, addresses issues with existing indices such as the Color Rendering Index (CRI) and the Television Lighting Consistency Index (TLCI) that make them inappropriate to describe lighting for digital cinema cameras - issues that have become more evident with the emergence of solid-state lighting (SSL) sources such as LED’s. The speed of sound depends on several variables, but the only independent variable we need to calculate the speed of sound is the temperature of the air. multiply by the number of units of the time component in a day (i.e.The Academy of Motion Picture Arts and Sciences, working with cinematographers, cinema lighting experts, lighting manufacturers, and lighting, imaging, and camera scientists and engineers, has developed a new index for the spectral evaluation of lights.Ok, so Salesforce's example date/time formulas reveals a less painful way to extract the hours/minutes/seconds. This is something I'd do in Apex (and store in a dedicated field that you can bring into your report), where we have variables and thus wouldn't need to repeat the hours calculation again to get the minutes calculated (and then both the hours and minutes calculations to get the seconds calculated). While this is possible to do in a formula in theory, I imagine it would be a pretty painful formula to write (and it might go over the formula compile size limit). Which with some simple math you can turn that into hours/minutes/seconds (12 hours, 54 minutes, 8 seconds) 5376 is the number of seconds (represented as a fraction) in a partially elapsed day if your two operands aren't exactly x days apartĨ6,400 seconds in a day would mean 0.5376 = 46,448 seconds (approximately) The 2 (or rather, everything to the left of the decimal point) is the number of whole days between the dates. ![]() This'll give you a result like 2.5376 where: You can simply subtract one date/time/datetime from another (e.g. ![]()
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