35mm Equivalent Focal Length

Saying a lens is 50 mm only describes the framing if the sensor size is known. Since the 35 mm frame became the reference everyone carries in their head — 50 mm is normal, 24 mm is wide, 200 mm is telephoto — converting the real focal length into its equivalent in that format is what lets you compare different equipment.

Enter the focal length and your sensor's crop factor and the page returns the equivalent. The arithmetic is a simple multiplication, and the result answers the practical question: a 35 mm lens on an APS-C sensor frames like a 52.5 mm on full frame, which means it stops being a wide angle and becomes a normal lens.

It pays to be clear about what the number does not say. It describes the angle of view only — perspective, blur and background compression remain those of the real focal length. A 35 mm on APS-C frames like a 50 mm, but the background blur is that of a 35 mm, which is less. That is why photographers speak of framing equivalence and depth equivalence as separate things.