Prior to about the mid 1980s when zoom lenses became prevalent, if you were in the market for a new camera, chances are it came with a “standard” or “normal” lens with a focal length of 50mm, or somewhere close to that.
In the early days of SLRs, standard lenses were often a bit longer at 58mm, and by the 1970s, many fixed lens cameras had standard lenses a little wider, in the 40 to 42mm range but still, these lenses were considered have a “normal” focal length. Anything wider than the kit lens was a wide angle, and anything longer was a telephoto. It did not matter what brand you were buying, or whether it was an SLR, a rangefinder, or a point and shoot, most cameras had something close to 50mm.
But why? Why did ~50mm become the de-facto standard lens for so many cameras?
I’ve heard a variety of so-called explanations for this. Some of the more common ones are that 50mm lenses most closely approximate the focal length of the human eye, that 50mm lenses allow for the simplest (and cheapest) lens formulas, or that 50mm is the most flexible focal length that is neither too long nor too wide.
The explanation of a lens that most closely matches that of normal human vision makes sense as if a camera “sees” what we “see”, then that has to be normal, right? But everyone’s eyes are different. Some people have better peripheral vision than others, so what what one person sees as normal, someone else might not. And if humans did have a static focal length to our eyes, why did the normal lens keep changing? 50mm is not the same as 58mm, nor is it 42mm.
As for complexity of lens design, sure, a whole boat load of 3-element Trioplans and 4-element Tessars were produced over the years as the standard lens on many cameras. I am sure that by the 1960s, Meyer Optik and Carl Zeiss Jena could churn out these simple lenses in a matter of minutes, but how does that explain all the more complex 50mm 6, 7, and 8 element lens designs? Heck, Nippon Kogaku’s Nikkor-N 5cm f/1.1 rangefinder lens has a whopping 9-elements, so that sorta kills any assumption that a 50mm lens was always simpler to make.
Of the three explanations, the flexibility of a normal focal length that’s neither too wide or too long makes the most sense to me, but if you want to know more about the history of these lenses, this week’s Keppler’s Vault from the September 1970 issue of Popular Photography attempts to answer that question.
Author Bob Schwalberg takes a deep dive into the history of the 50mm lens and gets a bit technical throughout making this one a bit more of a challenging read than the typical articles I like to share, but if you really want to know more about normal lenses, it’s worth reading as there is not a single cut and dry answer.
For a simpler explanation, it’s probably no surprise that the reason for the popularity of the 50mm lens has something to do with Oskar Barnack as that was the focal length he chose on the original Leica prototype. All of the original Leicas had fixed 50mm lens, so without any ability to alter the focal length of the camera, Barnack chose a lens that offered both the best compromise of wide and long, while offering a resolution that could be satisfactorily blown up to make prints.
For much of the first half of the 20th century, 50mm lenses were the norm until the late 1950s when the first SLRs were produced with 58mm lenses, which the article says was done both to more easily clear the moving mirror on early reflex cameras, but also to give a closer to 1:1 image on the SLR ground glass. With a slightly longer focal length, SLRs are easier to focus, and early SLRs having darker viewfinders meant that “seeing focus” was a bit more challenging on wider lenses.
Something interesting in this article which I’ve never seen mentioned anywhere was that at one point, there was the thought that perhaps 85mm to 105mm lenses would become the “normal” SLR focal length for that focal length’s ease of achieving a sharp focus and that some photographers preferred those as portrait lenses. While I do not deny the benefits a mild telephoto lens has for portraiture, I am quite glad this idea never gained any traction.
This article was written in 1970 at the very beginning of an increased use of 40 and 42mm standard lenses, so it doesn’t touch upon these too much, but with the popularity of cameras like the Rollei 35 and it’s ultra compact lens design, slightly wider normals would become favorites of simpler rangefinder and scale focus cameras due to increased depth of field, and a more compact size.
As you might image, the question “Why do so many lenses have a 50mm focal length?” doesn’t have a simple cut and dry answer. A combination of many factors contributed, but after reading this article, I feel as though saying “flexibility” is probably the simplest.
All scans used with permission by Marc Bergman, 2021.