Search the Community

I have read ARRI's whitepaper on dynamic range and how the EI is used to assign which signal value we want to choose as middle grey, which ultimately allows us to control the exposure latitude around middle grey. I've also read that the way ARRI does this is by only allowing us to shoot at its native ISO 800 (or maybe as some say its 400) and that changing the EI is like adding an exposure LUT on our image. This would make sense to me, because it would explain how the dynamic range (SNR=1 to full well capacity) is able to stay constant at different EI, because it doesn't operate by increasing the gain of the signal. (It would also explain why its they use the nomenclature EI) Nevertheless, I would like to know how they do this and if what I have read is correct?

Hey, I was reading through Kodak's 'The Essential Reference Guide for Filmmakers' and came across the following: A word about film speeds You probably know that motion picture films use exposure index (EI) to indicate speed. Although similar, EI is not the same as the ASA or ISO speed used for still films. EI denotes a somewhat conservative figure related to the higher quality requirements of motion picture film that must be projected onto a large screen. Typically the EI speed is about one stop lower than ASA or ISO. EI 500 film, therefore, is the equivalent of ASA/ISO 1000. Is anyone able to develop further on this? It is the first time I've come across the concept that EI is not the same as ISO. If I take what is written literally, does this mean that I should be setting my light meter to read at 500 instead of 250 (assuming I am shooting on say 250D stock) to get correct exposure? All the best, Connor