Focal Length Distance Equivalency?

[chris00nj]

I was wondering whether there was a calculation where you determine the distances where focal lengths are equivalent. For example, if I am looking through my viewfinder with a 50mm lens and I am 15 feet from the subject, how far away from the subject would I have to be with a 135mm lens to get the same frame?

 

[pvdhaar]

It's actually rather simple: (135 / 50) x 15 = 40.5 ft.

 

[payasam]

With an M Leica there's the practical method of using the different frames. However, I don't see why you should want to record a subject or object at the same size on your film with different lenses.

 

[chris00nj]

It's actually rather simple: (135 / 50) x 15 = 40.5 ft.

Thanks for the tip. I'm trying to judge what size I may need for shots on my trip (to Rome).