* wider f-stop
* less chromatic aberration
* less distortion generally
* smaller circle of confusion
The chromatic aberration is an important but subtle effect. Remember that lenses are multiple pieces of glass, and every interface diffracts the wavelengths of light like a prism. One of the considerations in lens design is converging all those different wavelengths of light in the same place. Not just at one point, but at every point across the image plane.
Poor lenses might do the well in an area. Good lenses do it everywhere.
Sorry, should have clarified. The lens in particular that made me rethink everything else I had was a 70-200mm f/2.8L. Zooms in particular often suffer from sharpness and chromatic aberration issues compared to a prime due to the larger number of optics. This lens did not. I’m sure a comparable prime stuck next to it would still show it up, but coming from kit zoom lenses, it was quite a shocking difference.
The static aperture also helps tremendously of course, yes - nice bokeh with a tight zoom means you can easily get candid portraits that look great from anywhere in the room.
70-200 f2.8 L IS III is the Bentley of lenses, the Aston Martin, the Maybach, etc. you got the best hardware possible for the job. for the price it better be amazing! even the older ones without IS are excellent.
L glass is also a very interesting used market - those things basically don't lose value IME.
It was the IS II at the time, but yes - an absolutely spectacular piece of kit. I think it was about $100 to rent for the weekend? Very reasonable IMO, and made me realize that one could quite easily bootstrap a wedding photography business without actually owning gear.
Other than the actual business side of things, pesky details like getting clients. And the massive stress of shooting a wedding. I was happy to do it gratis for family, but I don’t think I’d want to deal with paying clients.
When I was still shooting Canon, I used a 70-200mm f/4L which I picked up for a song (C$~600 sixteen years ago?). Not the beauty of a 2.8, but having a consistent 4 made for some beautiful shots on Cape Breton.
Lenses affect color contrast too. I don't fully grasp it but internal reflections adding neutral white bias or correction tradeoffs between geometry and color or something. Aperture can be widened as much as lens barrel allows so that isn't it.
-- more control of depth of field / shallower DoF ability?
-- faster shutter speeds?
-- less chromatic aberrations?
It doesn't intuitively feel like sharpness should be a factor -- even cheap kit lenses usually get that right.