For years I've been hearing cheapskates whine about how their cheap prime lenses are "just as good" as my expensive zooms. Herewith we give it a try.
I avoided primes for years, but finally gave in to their faster speed. For shooting bands in dark bars--any bars, really--f/2.8 just isn't going to cut it. And that's the best the expensive zooms can do; if you have a lens that varies the aperture from f/3.5 to f/5.6 as you zoom out, you might as well shoot with your telephone. (Which has an aperture of f/1.8, if it's a recent iPhone.) I rarely use my zoom lenses in bars now; even with the great low-light capability of a Canon 5D Mk IV, I'd rather have two stops of lower noise. It goes like this: my Canon 70-200 L Lens has a maximum aperture of f/2.8, which means I'm shooting at ISO 6400-12,800 to keep my shutter speed up where I like it at 1/200th or better. If I use a Canon 135mm prime, with a max aperture of f/2.0, my ISO gets cut in half. That makes a huge difference. Even better are the Sigma 35mm and 85mm lenses at f/1.4 or a Canon 50mm at f/1.2. Now ISOs are down in the 1600-3200 range, and everything is sharper.
Everything is sharper if I shoot it right, that is. The biggest problem with those fast primes is the tiny depth-of-field. Download an app and check; I use Simple DoF but there are others. A nice closeup of the singer from 10 feet away gives a depth of field of about +/- 2 inches with an f/1.4 85mm prime. That doesn't seem unreasonable if you're used to shooting portraits. . .but musicians on stage rarely hold a good pose while you focus-and-recompose. So, using primes means my number of sharp shots decreases, but the ones I do get are crisper and less noisy because of the lower ISOs. I have to admit: despite my earlier bias against prime lenses, I'm hooked on them now. If you're shooting bands in bars, you probably out to get hooked, too.
Now, a few years ago I was still enamored of my zooms so I did this little test. The prime lenses I had at the time were Canon's cheap stuff: just a couple hundred bucks. Now I've upgraded to their primo "L" lenses and yeah, they're noticeably sharper than the zooms. Well. . .they are noticeably sharper on my big 27-inch monitor. I doubt people see any difference on their cellphones. So if you are not completely obsessive about shooting bands, get a couple of the less expensive primes and use them for just about anything less than a stadium. Your work will stand out from the rest of the rock photographers. Here's what I wrote about the cheap primes a few years ago; I can't repeat the experiment since I sold all them, but the pix will demonstrate that they do a great job.
Canon sells a f/1.4 50mm lens for about $400. It's not one of their pro lenses; that 50mm runs about $2000, though admittedly it does open up to f/1.2. I never use my 50mm because, hey, I've got all these spiffy zoom lenses. Here I compared it to my 24-70mm f/2.8 lens, which runs about $1600 and is generally considered a go-to lens by professionals. I gotta admit. . .it's really hard to take some decent comparo shots. I didn't notice the glare; then the sun went behind a cloud and the white balance changed. The important thing, though, is sharpness and I have to admit if it weren't for the captions, I wouldn't be able to tell which was which. These are at approximately 100%; I also looked at 200% in Lightroom and I still couldn't tell anything significant. I ran the standard version of Nik Sharpener Pro on them--yeah, you could say that changes things but look, I always sharpen pictures so who cares how they look out of the camera? I don't think Nik's smart enough to sharpen one side more that the other. Anyway: if I can't tell at 100% or 200%, surely it's not important at normal screen or print sizes. Looks like those cheapskate wienies were right.
So, how about the Canon 85mm f/1.8 lens? It only costs about $360 these days; should be a nice portrait lens, but is it as good as my beloved $2200 70-200mm f/2.8 L II lens, the Holy Grail of zooms? For that matter, how does it stack up against the cheaper but still excellent $1050 24-105mm f/4 L lens? Well, we'll see. But first I have to point out that I noticed my 24-105 is not aligned or calibrated or whatever; I had to zoom in about 10mm more to equal the 85mm focal length of the prime lens or the other zoom. That's why the label says 95mm instead of 85; I wanted to get the picture size equal in the camera. And again, if it weren't for the labels, I doubt I could correctly identify which pic was taken with the expensive lenses.
I'm not sure you can tell much from these jpegs--except that you can tell there isn't much to tell. Primes aren't imaged-stabilized; you lose the ability to zoom and you end up carrying a buttpack full of them so you can swap lenses every few minutes and cover all the shots you could have gotten with a pair of zooms. But I still recommend them.