Why are 50mm no longer the default kit lens for prosumer SLRs?

Question

Every time someone asks me for a kit recommendation I point them towards some sort of prime lens with a standard focal length. Similarly, almost anyone I talk to about the ideal budget kit swears that fixed lenses get much better quality photographs than similarly priced zoom lenses.

What factors contributed to the revolution of the default 'kit' lens changing from a 50mm prime to a zoom lens in consumer and prosumer grade cameras. Why wasn't the 50mm replaced by the 35mm lens, which would be standard on a crop sensor? I am interested to know from a manufacturing and distribution point of view why broad range variable zoom lenses replaced the default SLR lens.

Answer 1

Presumably because the people who buy their first DSLRs mostly come from the point-and-shoot world and care about the versatility afforded by the zoom more than about image quality. Also, a 50mm is way too long to be a good "default" lens with an APS-C camera, and good-quality ~30mm lenses are, due to certain quirks of optics, much more complex (and thus more expensive) than 50mm ones.

Also, the sort of image quality now common even in cheap kit lenses was simply not possible to achieve in an affordable zoom a few decades back. A prime was back then pretty much the only option.

EDIT

To elaborate on what I meant by "certain quirks of optics", lenses with focal length shorter than the flange focal distance (or register distance) have to employ a special retrofocal design to make the optics work out. This basically entails adding a reverse telephoto group in the rear of the lens. The register distance of the Canon EF and EF-S mounts is 44 mm; Nikon's F mount has 46.5 mm.

This question has a good answer by Matt Grum with some illustrative pictures.

An APS-C camera could probably be designed to have a correspondingly shorter register distance, but it would be incompatible with lenses designed for full frame.

Answer 2

There are a number of reasons why the 'kit lenses' we have now became commonplace.

Back in the early 90's (when I started out) zoom lenses were heavy, bulky, suffered compromised optics and came with a big price premium even at the budget end. Lens makers had been working on those issues for a long time anyway and by the end of the decade the value gap (price/quality/versatility) between prime & zoom had already become insignificant enough to make zooms the kit lenses with new film SLR's years before the advent of digital bodies.

How the zooms got better and cheaper is a story of incremental improvements like most technology. If you're interested in reading more about lens development Nikon have a series of articles on their lens design history.

Answer 3

User convenience. Zoom lens quality and speed is good enough for everyday use and the convenience of being able to change framing instantly, trumps the gains in quality from primes.

The zoom thing is not universally true, however, because there are some (expensive) cameras such as Fuji and Leica models that have a fixed 35mm lens, which is the 50mm equivalent.

Answer 4

What sells cameras on the entry level? Convenience. It is very rare to have an entry level consumer whose primary concern is image quality. If it was, they wouldn't be looking at entry level and would be looking at a body only solution with a good lens.

Instead, the vast majority of entry level DSLR users are looking for something a little bit better than what they have that isn't significantly harder to use. This is why the emphasis is put on usability. Simple cameras with simple modes that make life easy, with basic lenses that will still do a little bit better than the point and shoots (enough to justify the move up), but also preserve as much of the functionality that the consumers in that market segment have come to expect.

As you move up in to the (much smaller) portion of the crowd that care more about quality and actually know photography, you are looking at a crowd that has a) been around a while and b) likely has already accumulated some lenses that will go with the camera, so they are either going to be buying body only setups or won't particularly care that the lens is included.

This is also kind of similar to why a fairly limited number of APS-C only lenses are available since the majority of people who are buying lenses are also likely to move up at some point or atleast will buy the better quality optics that will work for both.

Answer 5

The answer to the first part -- why at all? -- is simply consumer demand. The mass market likes the convenience of zoom.

And the answer to the second part -- why not 35mm kits for crop sensor DSLRs? -- is twofold.

First, all of the main crop-factor DSLRs use a (possibly slightly modified) version of the older full-frame mounts, so even though their is a crop, the lens designs aren't radically different. This means that 35mm lenses are still more expensive than 50mm lenses. More on this at Why are 50mm Lenses Cheaper?

Second, the change had already been made, long before digital. For example, Canon's first EOS film camera in 1987 came with a 35-70mm f/3.5-4.5. So, by the time digital came on the scene, we saw 18-55mm kit zooms made to match the equivalent 28-80mm film camera kit lenses. It was only more recently that demand enthusiast photography market brought lenses like Nikon and Pentax's budget 35mms to us.

Answer 6

There was one very good reason to have 50mm primes as the standard on SLRs into the 1970 and 1980s: Films in common use were far slower back then, so you depended more on lens speed, and a 50mm prime can be and was easily made f/1.something economically - a f1.something zoom lens, especially at 35mm full frame size, would be an expensive, bulky exot even today.

With ISO 100/200/400 films becoming common and affordable, the convenience and versatility of a zoom lens started to be more relevant than the added lowlight capability - especially given the fact that 50mm primes were and are still available for whoever needed them.

Also, to many buyers, the addition of an included zoom lens with a new camera looked like an exciting new feature if they came from a 50mm-only background. Possible image quality issues were most likely rarely even noticed - most manufacturer kit zooms even in the 1980s were not THAT shabby in optical quality, and most users chose small prints as an output medium anyway, or used inexpensive slide projectors where the projection lens was perceived as the most likely reason for mediocre image quality.