Some lenses have an aperture range in their name. I’m going to use the example of the Sigma 60-600mm f/4.5-6.3 DG OS HSM Sports lens here, but there are plenty of others that also have an aperture range in their name.
It’s just one of several confusing things about how lenses are named.
This particular issue only applies to zoom lenses, and only some zoom lenses at that.
Most of the time, lens manufacturers use the convention of including the lens’s maximum aperture as part of the name. So you might see lenses such as a 24-70mm ƒ/2.8 or 200mm ƒ/4. But sometimes there’s more than one aperture.
In this example, the ƒ/4.5-6.3 part of the lens’s name refers to the maximum aperture. So this lens has a maximum aperture of ƒ/4.5 to ƒ/6.3 depending on the zoom. When zoomed out, the maximum aperture is ƒ/4.5. When zoomed in, the maximum aperture is ƒ/6.3.
You could be forgiven for thinking that it means that it can only shoot between ƒ/4.5 and ƒ/6.3, but that’s not what it means. You can shoot at smaller apertures than that, such as ƒ/8 or ƒ/16, down to whatever the lens’s minimum aperture is.
Things Worth Knowing
- As I said, this only applies to zoom lenses. And only some zoom lenses. It’s a result of the optical design.
- Higher-end lenses (i.e., more expensive and, often, faster) often have a constant maximum aperture through the zoom range. For example, the Sony FE 24-70mm f/2.8 GM II is a zoom lens, but the maximum aperture of ƒ/2.8 is available regardless of whether it’s zoomed out at 24mm or zoomed in at 70mm.
- The minimum aperture isn’t included in the name—that’s something that you find on the spec sheets or on the aperture ring or by using it. But the same kind of optical design decisions can affect the lens’s minimum aperture. The Sigma lens I referred to above is a good example because its minimum aperture shifts between ƒ/22 and ƒ/32 according to the zoom setting of the lens.
- There is at least one case where a lens’s maximum aperture can change but that isn’t included as part of the lens name. Some macro lenses will have a different maximum aperture available depending on the focus distance. For example, it happens on one of the lenses I use regularly: the Nikon AF-S VR Micro-NIKKOR 105mm f/2.8G IF-ED. From the name, you’d see it’s a prime medium-telephoto focal length with macro (Nikon uses “micro” instead of “macro”). And from the name, you can tell it has a maximum aperture of ƒ/2.8. But when you actually go to use the macro part, you’ll find that when you focus close, you can only stop it down to ƒ/3.3 and can’t go any further. You get the ƒ/2.8 available at larger focus distances.