Why do so many APS-C kit zoom lenses start at 18mm?
Asked 5/22/2018
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I’ve noticed a lot of kit zooms for APS-C cameras begin at 18mm, such as 18-55mm, 18-70mm, 18-135mm, and 18-200mm. Is there something special about 18mm, or is there a design/format reason why manufacturers so often choose that starting focal length?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
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It's mostly because the standard zoom kit lens for film cameras would start at 28mm. This is the widest you can typically go before hitting the more expensive exotic glass.
The APS-C field-of-view equivalent for what 28mm on full frame looks like is 18mm. So that's what most kit lenses for APS-C sensor cameras use. You'll note further down that list that for four-thirds gear, the kit lens starts at 14mm. Four-thirds has a 2x crop factor, so a 14mm lens also yields the same equivalence as a 28mm on full-frame. And the kit lens on the Nikon 1 cameras, which have a 2.7x crop factor is 10mm, yielding very close to a 28mm FoV equivalence.
There's nothing magical about the number, just that it's the easiest wide angle to develop a low-cost zoom lens for.
Originally by user27440. Source · Licensed CC BY-SA 4.0
user27440
8y ago
0
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There’s nothing inherently magical about 18mm. It’s common because it’s a practical, inexpensive wide end for APS-C kit zooms.
Historically, many film-camera standard zooms started around 28mm on full frame, since going much wider usually required more complex and expensive lens designs. On APS-C cameras, 18mm gives a similar angle of view to about 28mm on full frame because of the smaller sensor’s crop factor. That makes it a familiar, useful wide end for everyday shooting while keeping the lens affordable.
You can see the same pattern on other sensor sizes: Four Thirds kit zooms often start around 14mm, and Nikon 1 kit zooms around 10mm—both chosen to give roughly that same 28mm-equivalent field of view.
So the reason is mostly sensor size plus cost and design practicality, not that 18mm itself is special.
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