Tuesday, April 27, 2010

The "neutral" focal length

A focal length between 40 and 50 mm, on the traditional 35 mm film format, is usually accepted as the one that more closely matches the field of view of human vision. That is often called a neutral (or normal, or standard) focal length. On APS-C sized sensors that would correspond to about 28 to 35 mm and on Micro 4/3 sensors to 20 to 25 mm focal lengths.

I've never been a particular fan of neutral focal lengths. Back in my days of 35 mm film, my favorite lenses were the 25, 35 and 85 mm primes. Now, with my Pentax DSLR, I have been using mostly 35, 75 and 130 mm equivalents. Can you see a trend here? I've always bypassed the 40 - 50 mm range, and I've never really missed it. I've always thought it would be difficult for me to produce good images with such focal lengths. One can't resort neither to the dramatic views and superimposed planes of wide angle lenses nor to the detail and subject isolation of longer lenses. All that can be done is careful composition. And that, my friends, demands a certain amount of skill.

Olympus E-P2 + Panasonic Lumix 20/1.7

I've bought a 20 mm lens with the E-P2, which is equivalent to 40 mm - right on the neutral zone. I'm not too happy with the aesthetic quality of the images I've gotten so far. Have to keep trying. Many masters of photography created beautiful works using 50 mm lenses attached to Leica film rangefinders. The problem is certainly not the length of the focal, but the skill of the photographer using it...

PS [Apr 28, 2010]: This interesting article by Andy Westlake discusses what a "standard" lens is supposed to be. According to him, the proper "theoretical" values are 43 mm for full-frame/35 mm film, 29 mm for APS-C and 21 mm for Four Thirds. But the usual convention tends to be: 50 mm, 35 mm and 25 mm respectively.


Tyler Monson said...

I always thought the 35mm lens was the 'normal' for 35mm, and the 21mm closest to that on the reduced digital APS format.
Trouble is, I've been around way too long to remember where I first learned that. But it has worked for me, in all the formats I've used.
In Leica days, I carried a 35mm and a 90mm (and used the latter so rarely that I stopped carrying it).
I've never much cared for 'standard' focal length lenses.

Frank M. said...

Hi Tyler
It is all very subjective, of course. Just like the way reality is perceived.
Anyway, I've added a link at the end of my post to a web article that discusses this issue .