I was given a chart by a friend for Efke 100 & found Andrew O'neil's times for Efke 25 on the web ( believe at LargeFormatPhotography.info ). Here's a link to a previous discussion on Efke reciprocity. Matt Miller's times of 60 sec -> 8 min 45 sec for Efke 100 shows comparable findings. My limited experience with low-light situations suggests that Efke 100 as well as J&C Pro 100 are very unreponsive whereas Efke 25 may be a good choice if you want sharp detail without the grain of faster films.