Hi all, just returned from a car boot sale with a Petri Computor 35 in gooid nick. The rangefinder appears to have become decoupled but thats not an issue as I plan to use it in pre focus mode based upon approximate distance. it has a 40mm lens. Now my question is: what sort of depth of field am I likely to get at say f5.6 when focussed at 7 feet? On my 28mm lens I set at about 7 feet and everything is in focus between about 5 feet and 15. is there any resource to give me a clue?