Lens Choice 101: Gap, Adjoin, or Overlap?

As I was contemplating a new lens recently, I realized that there's a subject about lens choice I haven't really written about. 

The minute you move from using just one lens to more than one, you start getting into questions of why and when to change between lenses. Three basic overall scenarios developed over the years, which most photographers use in some form or another:

  1. Stack of Zooms. The zoom lens trio of wide-angle zoom, mid-range zoom, and telephoto zoom is one of the most prevalent choices among pros and many serious photographers, whether f/2.8 or f/4 or even variable aperture (Nikon, to its credit, made all three choices in the F-mount, as did Canon). The primary objective to this approach is getting a broad angle of view coverage, typically 14-200mm in terms of focal length, but sometimes different than that.
  2. Stack of Primes. Photographers who prefer certain angle of views of fast apertures sometimes gravitate to a kit of just prime lenses. Historically, we've had 14mm, 18mm, 20mm, 24mm, 28mm, 35mm, 50mm, 85mm, 105mm, and 135mm as common focal lengths (plus 200mm+, which tends towards the more expensive exotic type of lens). In the basic set (from 20 to 85mm) we tended to have f/1.4, f/1.8, and f/2.8 lines of lenses to choose from.
  3. Zoom(s) plus Prime(s). The s's are in parentheses here because the most common scenario I encounter among amateur photographers is a variable aperture superzoom (or extended mid-range zoom) plus a fast wide or normal prime for low light situations.  

Obviously, other scenarios abound, as well. But in every scenario you have to think about angle of view coverage. What can you cover from where? The "from where" part is that most amateurs tend to overlook, or they simplify things by just saying "from where I am." "From where" is about perspective, and that's a very important thing to control in your photography. It's one of the key components to photographic style. 

"What you can cover from where" is all about focal length choices. In Scenario #1, for instance, the reason why photojournalists tend to carry those three zoom lenses is that the answer becomes something close to "anything from (almost) anywhere." 

But let's consider a two or three lens zoom set for a moment. You'll find that you actually have choices about how the lenses align with one another:

  • Overlap. Here, we have focal length overlap in play. For example, a 14-30mm and 24-200mm lens (e.g. popular Z System lenses) have a focal length overlap from 24-30mm. Advantage: in edge cases—in the overlap zone—you're not taking the lens on the camera off and risking missing a photo. Disadvantage: most of the "overlap" type lenses tend to be slower or variable aperture.
  • Adjoin. In this choice, we make sure that each zoom's focal range abuts the next. For example, a 24-70mm and 70-200mm lens (the most popular choices of the common zoom lens trio). Advantage: there are no gaps in your focal length coverage. You're also often able to choose fast or slower options, though strangely I see few mixing and matching (e.g. 24-70mm f/2.8, 70-200mm f/4). Disadvantage: when you're working a lot in the edge case, you're changing lenses a lot.
  • Gap. The final option is to allow a gap between your focal range coverage. For example, a 16-35mm and 70-200mm lens duo, where you give up the mid-range (Disclosure: the mid-range from 35-60mm is some of my least favorite focal length, so I often choose not to carry it). Advantage: you might be able to drop from three lenses to two while still covering a wide range of focal length. Disadvantage: there are images you can't take (don't tell me that you can move; again, perspective is the issue here, as you'll encounter subject/perspective situations you can't create). 

Let me tell you where I was pondering the above in my own decision making for a moment. I need a faster telephoto zoom for my Sony E system (I've been using the 70-200mm f/4). I have a 200-600mm zoom. So, do I really need the Sony 70-200mm f/2.8, or might I consider the smaller, lighter Tamron 70-180mm f/2.8? 

In this case, the gap from 180-200mm isn't particularly meaningful (though I did study close focus distancing for both lenses carefully, another thing to consider as you're building out a general lens set). On safari with two bodies, one with each lens on it, would I miss 180-200mm? No. On the sidelines of a football game would I miss 180-200mm? No. I already use a big gap there, because I'm either using a 400mm or 500mm lens on the second body. 

So I decided that gap/adjoin didn't make any difference to me in that decision. 

On the other hand, I already mentioned that I don't particularly use the 35-60mm focal range much. If I were contemplating putting together a minimal lens set for my Sony E bodies, might I consider the Tamron 17-28mm and 70-180mm (or the Sony 16-35mm and the 70-200mm)? You bet. Indeed, some that think like me carry a small "normal" prime for the middle "just in case." The new 50mm f/2.5 compact lens would be a good choice for that (for me; you might pick differently).

Obviously, if you only use prime lenses, you have gaps ;~). In that case, the question becomes "how big of a gap would you tolerate?" For me, large gaps are the norm when I'm working with primes. As in 24mm and 105mm only. Maybe in some situations I'll also carry a 50mm. But that creates large gaps: 

  • 24mm = 74° horizontal
  • 50mm = 40° horizontal
  • 105mm = 19° horizontal

Aside: Lens makers almost all use diagonal measurements for angle of view, but I don't know of any photographer who thinks that way. Which is why I always convert things to horizontal coverage. Canon has a useful Angle of View calculator you can use that reports horizontal coverage.

Readers are always sending me their current lens lists and questions about what lens they should get next. The thing I notice in almost every one of those lists is that not enough thinking went into them, most were the result of spontaneous choices over time. Maybe a lens got reviewed well, maybe it was on sale, maybe it was the only one in stock at the time that was close to what they wanted. Peppered in with the zooms that person has usually are some seemingly random primes, too. The problem here often is FOMO. People get convinced that if they don't have a lens for every possible scenario that they will miss a photo. Note what I wrote about the advantage of "overlap": not changing lenses in borderline situations means you don't miss photos. Not carrying a dozen lenses means that you don't develop back problems ;~).

From time to time it makes sense to go back and rationalize your lens closet. So as you do that, strongly consider the alignment process you've picked. Are you an overlapper, an adjoiner, or a gapper? Why? In looking at your lens usage—Lightroom's a real help here, but there are other ways to do such analysis—what are you actually using? I've been doing that analysis lately and finding that there are number of lenses I'm not really using these days. Thus, when I get a chance, I'll be selling them and simplifying my gear closet. 

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