Possible Duplicate:
How much distance should one move so that a shot that can be framed at xx mm be framed at yy mm?
I think the question is clear but I will provide an example.
To fill the whole frame with a subject using 60mm lens I have to be X
meters from it. With 35mm lens I have to be Y
meters from it. It's obvious that X > Y
but how to calculate the actual distance (let's say that with 60mm lens, the distance is 1 meter)?
y = x*(35/60)
? Not sure about this, hence not posting this as an answer. \$\endgroup\$