Perhaps a month or so ago, I started posting camera settings with every photo I put up - it was the one thing I seemed to get asked about the most, and I'm very happy to share it because it provokes some comments and lots of DMs. I'm still a photo nerd, and I love talking about this stuff.
One thing that seems to be remarked upon the most is when I post images that have an ISO that seems high...3200, 5000, 6400. In the "old days" of digital as well as analog photography, images shot at these levels would look as if they were printed on sandpaper. These days, however, that is no longer the case.
I've taken to shooting on Auto ISO...as someone who learned to shoot with film, the whole idea was weird to me. On film, the notion of an "exposure triangle" didn't really exist as it does with digital, especially on 35mm. You loaded your film, it was X number of exposures, so you were locked in to whatever ISO you loaded until you finished that roll. If you knew you were shooting at a darker time of day or in a darker area, you loaded higher ISO film, or pushed what you were shooting.
Now, though, you can set your camera to "ride" the ISO in the same way it will ride aperture in Shutter Priority or the shutter speed in Aperture Priority, which is incredibly useful. Even better, you can set the camera to stay within ISO minimum and maximum limits you assign it...in my case, I have it set to play between ISO 50 at minimum and 6400 maximum. Why these? Well, 50 is about as low as my camera (Sony A9) will go, and 6400 is the highest I've had to go anywhere in the building at the show. I've seen full-size examples shot at even higher ISOs that were perfectly usable.
Along with many other phtoographers, I'm a huge proponent of "your gear doesn't matter." Unfortunately, with the equipment I've used, this high ISO performance is one of the exceptions to that rule. The questions and comments about the high ISO photos I put out there generally runs along the lines of "what are you doing to these files to get them looking so good at 5000/6400?"
I haven't done a ton of testing like the folks with the YouTube channels, but in my experience the answer lies in a few different things. First - and I am not a fanboy or an "ambassador" or sponsored - but the Sony A9 is an exceptional camera when it comes to shooting in low-light situations. Mirrorless in general is so great for shooting in low light...the ability to crank the brightness in the viewfinder so you can actually see what you're doing is something I never gotten tired of even after a few years. But where the camera really shines is when you open the files and find that they're not nearly as noisy as what you're accustomed to seeing at 6400. It's just got incredible performance at that ISO. When I first started shooting at the Daily Show, I was using a Canon 5D Mark III. It's a great camera, and there are a bunch of things I miss about it, but I never went above 3200 on that camera, and even then it was starting to look a little rough. It was released in 2012, and that's where the tech was back then. The A9 was released in 2017.
Also, tangentially, the A9 has a different stabilization system than any other camera I've ever worked with. The very first images I opened immediately looked crisper. The lower-light images I've made generally aren't shot at very slow shutter speeds (the usual answer to low light....slow the shutter, open the aperture) but I think even at higher speeds it makes a difference.
Second is that I do all my processing in Capture One (not sponsored by them either). I've mentioned many times that I've never used Lightroom to process my photos. It's a weird limitation, but I've just never had occasion to learn it...I didn't own it, and all the professionals whose shoots I worked on all used Capture One. I never tweak the noise levels in my images, I just leave it at whatever the default is.
And finally - this is purely subjective, but I think it matters - the vast majority of the images I shoot at those high ISO levels are eventually going to be made black and white. In black and white, all that sensor noise that might run into magenta or green is desaturated into...grain, essentially. And for photographers who have studied older work, we're used to seeing grain. It doesn't look strange, or off. It looks like grain.
I think the key takeaway here is that the Sony A9's low-light capabilities is the main factor in why photographers who see my images are surprised that they're made at 6400 ISO. In many cases I'm very happy to say that your gear doesn't matter, and that you in most cases make amazing images with whatever fairly modern camera is within your budget. But in the case of needing to shoot in low light, your gear will be a large part of your success.