I have been playing around with the Focus Bracketing feature on my R6 and I have found that the slowest shutter speed that I can use is 5 seconds. There is no information in the either of the R6 manuals mentioning limitations on shutter speeds when using Focus Bracketing. I was hoping that other forum members that have a R5/R6 might have any information on this matter. I have contacted Canon regarding this but they cannot help. TIA