Hello, BTZS suggest to incident meter the shadows and highlights, find the difference and add five stops to it to get Scene Brightness Range. - Look SBR vs EFS charts to find appropriate film speed. - Set the film speed in the meter and use shadow reading to determine the exposure. - Developing time is obtained from SBR vs Development time charts. My understanding is, when metering shadows the incident meter will place the shadows to middle gray then how we can use this to determine the exposure as according to BTZS method. Since, shadows will be on middle gray.