Kilgallb Subscriber Joined Oct 14, 2005 Messages 811 Location Calgary AB C Format 4x5 Format Jan 29, 2024 #126 Alan Edward Klein said: My cellphone has an app that shows a calibrated ruler on the screen. I suppose one could use that in a pinch. Click to expand... If you have a phone you have a calculator so use the formula d^2/f^2
Alan Edward Klein said: My cellphone has an app that shows a calibrated ruler on the screen. I suppose one could use that in a pinch. Click to expand... If you have a phone you have a calculator so use the formula d^2/f^2