Originally posted by DominicVII All right, I have difficulties understanding anything beyong basic mathematics, and I will present the problem in as simplistic a manner as possible.
The angle of view on 75 mm focal length on 35mm film is: 32 degrees.
The angle of view on 90mm mm focal length on 35mm film is: 26.9 degrees.
How many steps would I have to take back with the 90mm lens in order to attain the angle of view of 32 degrees?
All the online angle of view calculators only take into account the focal length; the factor of the photographer himself moving is not included in the equation. Are there any online tools that will solve the puzzle for me or does anyone here know of a simple way of calculating this?
You need an infinite number of steps back,
because the angle of view is a function of focal length and sensor size. I suspect, however, what you are really discussing is how many steps back to get the same magnification of a specific subject at a specific distance with a 90mm as opposed to your 75mm lens.
The answer is really simple math.
Image size = subject size x Focal length / subject distance
Since the image size on the sensor wants to remain the same, and the subject size remains the same, you will move back by the ratio of focal lengths, I.e. 90/75 times the subject distance at 75mm