> I do a lot of low-light, event photography, among other stuff, and the fancy expensive kit is just flat-out way better. I've shot thousands of these photos with both by now, and the extra technical flexibility is totally worth it.

Mm, yep. I do gig photography in small, dark venues -- I've shot probably 125 thousand photos at high ISOs, with six different cameras (Nikon DSLRs for the bulk of it, and Sony mirrorless experiments alongside in a parallel track).

> Hell, the extra sensor size and autofocus alone took me to a whole new level.

The difference in light gathering between an APS-C and full-frame camera of the same technological era is usually about one stop. If you make a several-year jump at the same time, that can be noticeable, I suppose.

> Do you know how much it sucks trying to do low-light with manual focus at a DJ performance because your autofocus can't keep up?

At gigs, I do quite a lot of manual focus (and single-point, back-button focus with manual adjustment). I have no particular issue with it and it helps solve problems autofocus simply cannot solve.

Especially with a Nikon, because you get focus point confirmation even manually.

You do a lot more thinking and observation about equivalent distance. For example if you cannot focus on someone's face because they are behind a brightly lit microphone that autofocus will always prefer: How far are they behind it? If you focus further down the microphone stand or on a belt buckle, lock and recompose on their face, without changing your position, how much does that correct it? Or can you judge how far in inches and then literally move yourself or your camera forward?

One good cross-type sensor is all you absolutely need (stay away from old-style Phase One autofocus kit if this bothers you!)

Admittedly back button focus makes that more useful. And focus peaking on a mirrorless camera is the bee's knees.

> How much time do you want to spend twiddling noise reduction controls because the entry-level kit's ISO 1600 looks like crap? How much shadow detail are you willing to sacrifice? It's such a pain in the ass.

I said above that the only thing that really forced me to upgrade from my S2 Pro was low light performance. But again, I think if I was to go back to using that camera, I would be getting results I wanted a whole stop, maybe a stop and a half faster than I did at the time, through better subject selection, better understanding of its limitations and fifteen years more understanding of exposure.

If you're talking about the D3100, I'd shoot that up to ISO 3200, I reckon. Its low light ISO performance is a little better than the D300 which I used for years at gigs with enormous success. And its dynamic range is not all that noticeably worse. As long as you are careful with your exposure, that's a useful little camera.

DxO Optics Pro/PhotoLab helps of course.

Newer kit does a lot of stuff better, certainly, and it can save you time. And yeah, low light photography is about the only place people run up against the limitations of older kit. But IMO nothing since 2008 has any kind of problem with low light, and in many cases the newer kit is tripped up by the exact same difficult situations.