I'm trying to work out whether a particular shot is feasible or not with my kit. I have an image taken at 24mm from the the spot I'd be shooting from. For the new shot I'll need a much narrower field of and I'm trying to calculate the effect of various focal lengths. I'm assuming that if I reduce an image by 50% on both height and width that will give me the equivalent field of view for a lens with twice the focal length. Is this right? If not, how can I can work this out? My method so far has been to reduce the original image size as above, double the focal length for an equivalent field of view, note the new pixel dimensions, and then repeat. Returning to the original, I've used the above dimensions to create white boxes at 15% opacity to give me an idea of how the shot would look with a longer focal length. Also, I need to work out how far I'll be from the subject so that I know whether my remote triggers will work. I can't simply measure it as the shooting position is in an elevated spot with restricted access). In my original 24mm shot, the subject was a certain size in the frame. How can I easily work out what the distance would be to have the subject the same size in the frame at a longer focal length? I was roughy 2m from the subject in the first shot, but it would be much better if I had a more precise figure. is it me or did Lightroom used to show the distance to subject (based on focus) as part of the EXIF information? If not, is it recorded in EXIF and if so what's the best way of reading it (for a Mac OS). Right, after all that I need a lie down!