Normal Field of View

In last week’s article Getting ready for Project 365 (2017) I wrote:

One aspect I need to improve on is to learn more about what my lenses see.

I further wrote:

I will pick a topic for each of the 12 months, such as using a Street Lens (24-85 mm) or Normal Lens (50 mm) only.

In preparing for what to write about this week, I started to think, which lens should I start with?

A 50mm Focal Length (FL) is thought as the equivalent of vision from one human eye. That’s classic old school focal length. Many call it the natural image angle. The 50mm prime lens was once the staple of the photography industry. The simple science behind the 50mm? It’s said to create natural looking images, especially when creating portraiture.

Remember that this is only valid for 35mm film camera sizes or Full Frame (FF) digital sensor. Since my Sony A77 has a APS-C sensor this converts approximately to a 35mm FL lens.

I don’t want to restart an endless debate if 50mm is correct or not. My take away, from the many on-line discussions is that:

  • humans perceive perspective and color on their ‘central vision‘, which is about equal to a 50mm FL on FF;

  • humans also perceive a ‘wider vision‘ around them, which lacks perspective and color information, and is about a 24mm FL on FF equivalent FOV; and

  • our ‘peripheral vision‘ extends a whopping 180 degrees, mostly recognize motion in this wider range, not shapes, which is about 12mm on FF, 8mm on APS-C.

Simply put, when using the ‘normal‘ lens, one can visualize what the camera sees without any compensation, it is ‘natural’. Of course, if you only see the final picture, and have no other references, you really cannot tell what actual FL it was, as long as you were using something in between 40mm to 65mm on FF, or in between 26mm to 45mm on APS-C.

With any lens, it is only through experience that one gets used to the focal length and becomes able to judge when to use it, particularly with the short telephoto effect on APS-C sensors. Your eye learns to ‘see’ with that focal length, and for any given situation you can decide whether it’s appropriate.

Back to my original question, which lens should I start with?

A 50mm FL on FF is a great, general purpose lens that’s good for lots of different types of shooting: portraits, night shots, etc. This makes it a good first lens for to start with because it is easy to imagine what images will look like before looking through the viewfinder. Since my camera has a APS-C sensor, the first lens I will be using is my Sony DT 35mm F/1.8 SAM.

By the way, a photograph is not exactly what the eye and brain saw at the scene. In the end a good shot is something different and something better, like what Garry Winogrand said:

You see something happening and you bang away at it. Either you get what you saw or you get something else — and whichever is better you print.