How Many Lenses Do You Need?
The whole point of an interchangeable lens camera is that it gives you the ability to change lenses. This leads to the obvious question of how many lenses you need.
I have a repurposed bookcase upstairs that I use to store cameras, lenses and assorted photographic accessories. I have to since I own more gear than I could possibly fit in even a couple of camera bags. I have sold some stuff over the years, but I hold onto more than I probably need to, just in case, or so I tell myself. I've been shooting various SLR and DSLR cameras for over 30 years now and at this point I freely admit I have more lenses than I actually need. At the other end of the spectrum, I suspect at least a few of you reading this now are fairly new to photography and may have only recently invested in an SLR camera. It would be pointless to buy a camera without a lens, but due to the initial investment required to get started in photography you may have bought only a single lens with that shiny new camera.
Some people prefer to stick with a zoom that covers a wide range of focal lengths, reasoning that it's more convenient not to have to change lenses. This means they have less to carry around and fewer opportunities to get dust on their camera sensor. There are some impressive zooms on the market these days but no lens can do everything, and those that try to rarely do everything well. Even with modern computer designed lens optics there are compromises necessary to create extended range zooms. Most have are variable aperture designs that limit the user to perhaps f/5.6 even at the most accommodating end of the zoom. Most such zooms also utilize a large number of glass elements that aren't always as sharp as they could be, at least at some focal lengths.
Others prefer to avoid zoom lenses entirely, sticking instead with a set of prime lenses that together stretch from wide angle to telephoto. Rightly or wrongly, prime lenses have always been lauded for sharpness. But while individual prime lenses may be excellent, not all are, and even if they were it would take quite a few to cover the full range from wide angle to telephoto. And all those primes take up a lot of space and collectively a reasonable bit of weight. And this doesn't even get into the hassle required to constantly change lenses to alter the framing from one image to the next. Moving your feet will also alter framing but also affects relative perspective that may not be what you want. Focal length and subject distance are not fully interchangeable variables.
At the core of my collection of lenses have always been a few fast zoom lenses: a wide angle, a midrange and a telephoto with a constant f/2.8 maximum aperture. Mind you, as I said at the outset, I haven't been able to stick to just three, but they do cover most needs. They seem to represent a reasonable compromise to the long range zoom versus prime lens purist debate that many people fall into either from choice or perceived necessity. The problem is though that they don't cover every possible need, and thus I occasionally need more lenses. And more lenses. Throw in a fish eye and a macro lens and I'm already up to five.
Just because you can change lenses doesn't mean you have to. Some people view the idea of changing lenses as a necessary evil, to be done only when necessary. Others view doing so as a feature to be taken full advantage of and thus they change lenses often. Different strokes for different folks and all that.
As to how many lenses you need, clearly the bottom line answer is that you need only one. Even though you can stack lenses, one reversed atop the other using the front one as a powerful diopter to magnify the other for high power macro, this is an exception and certainly not the rule. For most types of shooting, you use only a single lens at a time. For one shot, you need one lens, if you get my meaning.
So perhaps the real question is: how many lenses do you want? And once we shift to that question, there really are few limits. If you're not careful though, this can become a slippery slope. If you feel there's something lacking in your photography, buying another lens can sometimes be nothing more than a way to avoid dealing with what's actually limiting you.
Remember that a lens is just a tool to help you capture your vision. If you already have a basic set of lenses, push yourself to do more with the lenses you have before investing in another. You can always buy yourself another lens as a reward for a job well done — not because you need it, but because you've earned it.