I just bought a D7500, I had a D3100 previously. I'm using the camera in manual mode, shooting raw, and it's working incredibly badly in low light indoor conditions to the point that it feels something's wrong. I was shooting indoors in a room with lights on, while the lights weren't super bright, it wasn't incredibly dark, but I still needed shutter speed 1/80, aperture 4.5, and ISO at 800-1000 to get okay photos, and they were still dim. My 3100 worked way better in low light, I'm not sure if there's a setting I need to change.