I try to delete as I go...but I tend to keep pretty much everything unless its really poor. I do find however about only 5% I would say is suitable or "worth" further editing (PS,etc)for printing. Many are identicle shots with a differnt exposure or composition. I'll choose the one that looks best all around. Hopefully, as I get more experienced...the more "keepers". I've heard of Pros who go through hundreds until they find "that" shot. What's the verdict here. My case does not include family pics (holidays, etc).
Over 50%
