I am trying to figure out how big an object of, say, 50cm height at 100m distance and 600mm focal length would appear on a camera's sensor. The ubiquitous formula object size in image = focal length ...
I have to photograph 15cm high printed text from 500 meters away. The text has to be human readable in the result. What kind of focal length do I need? Can i compromise, and get a camera with less ...
So, I mount a 200mm lens on my Canon 450D. It effectively becomes a 320mm lens. Is this the equivalent of 320mm on a full frame camera? That is, from what I've figured out I get an equivalent field of ...