I saw it was about 4 of the widths of the still images, density at the centre close to 1/30 exposure 4in in 1/30 = 120 in/sec The darker edges are due to the period of time during the exposure the sensor see's the black (er) background compared with the target The actual density must be lighter as 4 inches compared to the 1inch actual size means there is a proportion of the background in all of the exposure. Perhaps I should have taken this into more account. Apologise for not putting my thoughts but I didn't want to spoil the puzzle with (mis)information edwin -----Original Message----- From: owner-photoforum@xxxxxxxxxxxxxxxxxx [mailto:owner-photoforum@xxxxxxxxxxxxxxxxxx] On Behalf Of ADavidhazy Sent: Tuesday, November 17, 2009 10:31 PM To: List for Photo/Imaging Educators - Professionals - Students Subject: Re: Sample question FYI Want to share how you arrived at that? The subject has initial size to begin with. It should be accounted for in speed determination by eliminating it - subtraction? Or did you do that? andy Edwin Blenkinsopp wrote: > 120 in/sec? >
