Focal length: gaps, ajoinment, 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 Focal Length Question
The minute you move from using just one lens to more than one, you start getting into questions of why and when to change lenses. Three basic overall multiple-lens scenarios developed over the years, one of which individual photographers tend to use:
- Quiver 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 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, and we're seeing that approach again in mirrorless). The primary objective to this approach is getting a broad angle of view coverage, typically 14-200mm in terms of focal length, which equates to a horizontal angle of view of 10° to 104° for full frame.
- Shelf of Primes. Photographers who prefer particular angle of views, perspectives, and fast apertures gravitate to a kit of just prime lenses. Historically, we've had 14mm (104°), 18mm (90°), 20mm (84°), 24mm (74°), 28mm (65°), 35mm (54°), 50mm (40°), 85mm (24°), 105mm (19.5°), and 135mm (15°) as common focal lengths (plus 200mm+, which tends towards a 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. Today we also have f/1.2 and f/2 options to confuse things.
- Superzoom plus Prime. 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 are possible, as well, but these three seem to be the most common.
In every lens set scenario you have to think about angle of view coverage. What can you cover from where? The "from where" part is one 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 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." The corollary is that photojournalists sometimes get stuck in one position, so they need multiple focal lengths to get establishing as well as detail images.
The Trickier Question
But let's consider a two or three lens zoom set for a moment (#1, above). You'll find that you have an additional choice: how the lenses align with one another.
- Overlap. Here, we have repeated focal lengths in play. For example, a 14-30mm and 24-200mm lens (e.g. two 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.
- Ajoin. In this (traditional) 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 from the common zoom lens trio). Advantage: there are no gaps in your focal length coverage. You're also often able to mix faster and slower options, though strangely I see few doing that sort of mixing and matching (e.g. 24-70mm f/4, 70-200mm f/2.8). Disadvantage: when you're forced to work in different focal lengths near the changeover point, you could be 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 due to the overused perspective, 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 will be 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 if you have a missing lens).
An Example
Let me tell you where I was pondering the above in a past lens choice decision. I needed a faster telephoto zoom for my Sony E system (I'd been using the 70-200mm f/4). I had a 200-600mm zoom for the longer focal lengths. So, did I really need the Sony 70-200mm f/2.8, or might I consider instead the smaller, lighter Tamron 70-180mm f/2.8?
In this case, the gap from 180mm to 200mm wasn't particularly meaningful (though I did study close focus distances for both lenses carefully, another thing you must 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? Still probably no. I already had a big gap there, because I was using either a 400mm or 500mm lens on a second body.
So I decided that gap/ajoin didn't make any difference to me in that decision.
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 current bodies, might I consider the Tamron 17-28mm and 70-180mm (or the Sony 16-35mm and the 70-200mm, or the Nikon 14-30mm and a 70-180/200)? You bet. Indeed, some that think like me carry a small "normal" prime for the middle "just in case." The Sony 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'll always 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 135mm only. Maybe in some situations I'll also carry a 50mm. But that still creates large gaps:
- 24mm = 74° horizontal
- 50mm = 40° horizontal
- 135mm = 15° 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 are often some seemingly random primes, too. The problem here is often just FOMO in GAS (gear acquisition syndrome driven by fear of missing out). 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 while changing lenses as often. Not carrying a dozen lenses means that you won't develop back problems ;~).
Art Wolfe, for instance, claimed in his presentations during the DSLR era that most of his images were from just two lenses: the Canon 16-35 f/2.8L II and the Canon 70-200 f/4L IS (note the gap, similar to mine). The only other two lenses he mentioned that he sometimes carried were the 24-105mm f/4L IS and the 200-400mm f/4 L IS USM (which provided some overlap plus a total focal range from 16 to 400mm). Four lenses total.
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 ajoiner, 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 did you actually use?
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.