RickL Loc: Vail, Az

I used a D810 for two years for nature photography until it met a tragic end. It is an excellent camera. Not familiar with the D750

gmccaleb1

Aperture priority 3.2 ISO 800 Nikkor 85mm lens

gmccaleb1

Aperture priority 3.2 ISO 800 Nikkor 85mm 1.8 lens

gmccaleb1

David, I haven't posted so long here, I've forgotten the format. I always ask for advice here because everyone is so knowledgeable. I shot in Aperture priority 3.2 ISO 800. My lenses are VR. These were way over exposed and that has something to do with the problem. I shoot a lot indoors with window light and much prefer that to a strobe. Plus, that's another big learning curve. I do need to practice more and see exactly how far I can go with the noise. Thanks for all the tips and I'll check out that book!

RickL Loc: Vail, Az

I shoot manual for landscape and manual plus auto I SO for nature. I used that setup with my D810 and use it now with my D850

justhercamera Loc: NW Michigan

What you were doing is very low light and noise would easily be an issue. I would expect to see it with the D850 as well. I have been looking at the Z6 and because it is full framed but only 24 mp, it handles low light very well, and with the in camera stabilization, it allows much slower speeds.

nikonuser750 Loc: Monroe, LA

This is the kind of picture I love to take with my D750. From the graphs I've seen, it comes close to the D850 in low light situations for a lot less money. I'd never want to ruin that picture with a strobe. I do have a great Nikon SB-800 speedlight but except for group photos and some other situations I always go with natural light when possible. The D750 is amazing in low light situations and you can certainly go above ISO 800 with no problems.

tomcat

The Z6 does handle low light very well. I use mine several times a week for basketball games in low light gyms, night time soccer games and for special events like plays and concerts. It delivers great shots at iso 8000-12000, especially when coupled with Topaz AI Clear. One thing that will make quite a big difference is high quality sharp lenses. The best 3 lenses I have are the Sigma Art series, the champion being the 135mm.

tomcat

I personally don't see anything wrong with this shot because it's a natural light image. I myself like 2 things in particular: the softness as it graduates away from the center and the way the image transitions from the chair into the shadows. The girl in the center appears to have a great focus and I can tell it's a shallow DOF. I really like what you did by capturing the exact precise moment of action and you could not have posed this shot any better. You definitely should print this and exhibit it.

jerryc41 Loc: Catskill Mts of NY

The D750 is a great camera (in my opinion), and it's my first choice when I go out shooting. I also have a Sony a6000 and Fuji X-T30 for when I need something small. Lowering the ISO will reduce noise. Combining that with a faster lens will help to keep the noise low. You can also process out a certain amount of noise.

I've bought lots of used and refurbished cameras on eBay and elsewhere. I'd look for refurbished before used.

jerryc41 Loc: Catskill Mts of NY

That's a great shot.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Either the D750 or D810 will do the job for you. The Nikon D750 was outstanding right out of the box. A new D750 is $500 over your budget but check refurbished. A refurbished one is only $50 over your budget.
https://www.bhphotovideo.com/c/product/1237482-REG/nikon_1543b_d750_dslr_camera_body.html?sts=pi&pim=Y

mymike Loc: Tucson, AZ

I wouldn’t upgrade until you try the suggestions on reducing the noise. You have two good camera’s and kids are hard to shoot.

Bultaco Loc: Aiken, SC

camerapapi Loc: Miami, Fl.

When I hear the word noise I am always curious about the ISO speed used, the technique and under which conditions the shot was made. Noise free cameras as far as I know are not available yet.
Some cameras do better than others but in general, with proper use ISO 1600 with cameras like yours should do a reasonable job. It is a common practice to ETTR or exposing to the right of the histogram shooting RAW data but without clipping the highlights. It is common also to use a denoise software and in my case I use Topaz Denoise AI that does a fantastic job to clean the images without taking away details. They offer a 30 day free trial.

Although it is common practice to use lenses made for full frame cameras with cropped sensors those lenses if they are teles do better than other lenses when used with those cameras. I prefer DX lenses for DX cameras because they use the whole sensor except for using teles which I do often for wildlife. It is very possible that you buy a camera such as the D750, an excellent tool and instead you find your images as noisy as you did with the D7100 at the same ISO settings you have been using. Change your technique and the difference should be obvious and consider a denoise program if still you want to keep the D7100.