As I have mentioned before, the standard Angle-of-View (AOV) of the human visual system (HVS) is about 60° (horizontally) – the central field of vision, so to speak. So why do companies still tout 50mm lenses as being “close to the angle of view of the human eye”? It’s honestly hard to know. Zeiss still describes its Touit 32mm f/1.8 as offering “…the same angle of view as the human eye.“, with a horizontal AOV of 40°. The dominant “standard” lens for full-frame has been the 50mm since the introduction of the Leica by Barnack in 1925. That’s nearly a century of using a lens that doesn’t really duplicate the AOV of human vision, mostly because it simplifies human vision far too much. It doesn’t even match the 43.3mm diagonal of the 36×24mm frame – which is normally the golden standard of a “normal” lens.
A 50mm lens has a horizontal AOV of 39.6°, which only comes close to representing the region of the HVS that deals with symbol recognition, which is a somewhat narrow scope. In fact, most people aren’t really concerned about whether they are using a lens that “approximates human vision”. One of the most talked about lenses in the Fuji-X environment is the 23mm lens, which is close to a 35mm in full-frame land. In all likelihood, there has probably been a gradual move away from 50mm towards the wider focal lengths. For example the iPhone 14 has two rear facing cameras: a 13mm ultra-wide, and a 26mm wide (equiv). No 50mm at all. With a wider AOV it is possible to crop from within the frame.
Some would probably advocate for the actual diagonal of a full-frame, i.e. 43mm. This would give an AOV of 45°, midway between 30 and 60 degrees. But is this optimal? I think it comes down to personal preference. I personally think that a 60° is likely a better approximation for a lens. So which lens better represents the 60°? For full-frame it is likely around 31mm, or around 20-21mm for APS-C. So we end up in the spectrum of wide lenses, and that’s not necessarily a bad thing. Humans visualize the world around them in terms of a wide lens – yes not all of it is in complete focus, but then the HVS works in much different ways to a camera lens.
Crafting Pixels 