what is the correlation between mm and field of view.

[Victor Nhat Nguyen]

I always wonder this. When you have maybe a 24mm and you switch to maybe a 50mm, does your field of view ( in degrees ) divide by half? and when you have a 100mm, your FOV divide by half again? What if you go from 24mm to 12mm. Then does your FOV increase by double? if yes, does that mean when you go to super ultra wide angle, each mm matters more than those mm in super telephoto?

 

[Samuel H]

In the "normal" and "telephoto" range, yes, it is roughly like that. As you go to the wide-angle side of things, it is less than linear. You can play with this: http://www.similaar.com/foto/dof/dof.php?f_x=1.6&f_r=1.77&f_mm=100&f_f=2.8&f_d=1.5 http://www.similaar.com/foto/dof/dof.php?f_x=1.6&f_r=1.77&f_mm=50&f_f=2.8&f_d=1.5 http://www.similaar.com/foto/dof/dof.php?f_x=1.6&f_r=1.77&f_mm=25&f_f=2.8&f_d=1.5 http://www.similaar.com/foto/dof/dof.php?f_x=1.6&f_r=1.77&f_mm=12.5&f_f=2.8&f_d=1.5 but even the formulas I used to make the calculator are just an approximation in the ultra-ultra-wide-angle range (in real life, things get weird in that end, and things like the type of image projection matter even more than focal length)

 

[Bruce Watson]

I always wonder this. When you have maybe a 24mm and you switch to maybe a 50mm, does your field of view ( in degrees ) divide by half?

Not exactly. You can calculate field of view thusly: angle_of_view = 2arctan(sensor_dimension / 2(focal_length))

Where sensor_dimension is whatever is the most important measure of the sensor to you. Many people use the diagonal measure, many use the horizontal measure. Do the math and see what answers you get.

 

[j1clark@ucsd.edu]

Not exactly. You can calculate field of view thusly: angle_of_view = 2arctan(sensor_dimension / 2(focal_length))

Where sensor_dimension is whatever is the most important measure of the sensor to you. Many people use the diagonal measure, many use the horizontal measure. Do the math and see what answers you get.

The two iPhone apps I use, give both Horizontal and Vertical numbers either degrees or feet/inches (meters) depending, on whether I'm looking for FoV or AoV... in most cases FoV in feet/inches is for either Horizontal or Vertical that is the really important numbers to come up with...