The biggest problem I have with DOF charts is estimating distance such as 171.45 feet of 97.34 feet. I have never been very good at that stuff. Wide angle lens es are not a problem. It the longer lenses that are hard to estimate DOF. Whil e looking at a sporting good catalog I noticed that they have some very good ran ge finders that can also function as binoculars (sp). Nikon makes one which wei ghs 10 oz and can provide measurements form 30' to 2400'.

Is this a silly thing to consider? Has anyone every resorted to using such a to ol in the field? Or perhaps using Polaroid type 55 film and louping the negativ e to check for sharpness is sufficient (which is what I currently do now with va ring degrees of success).