What are the best settings (ISO, shutter speed, aperture) or which mode should I use, to shoot night time portraits on Nikon D3500? Should I keep my flash on or off?

ISO aperture, shutter speed for portraits

Write this down: There are no BEST settings, only what the most optimum that the light demands at the time and light level of each shot.

You can be walking down the street at the same time and two compositions will require the optimum aperture and shutter speed at different values.

When not shooting a static object with a tripod, leave the ISO at auto and use the speed of a higher ISO.

If you are for instance shooting a static night cityscape or food alley with your camera on a tripod, and want everything in focus which requires a higher Fstop, use a low ISO for cleaner blacks as you are going to compensate the lower sensitivity with longer exposure times.

You can turn around on the same street and shoot a closer vignette of a particular food stand and you want people to be frozen, youu2019d then go back up in higher ISO with the widest opening on your lens so you can shoot at a faster shutter speed to freeze the action.

BTW, a monopod with a tripod base on the bottom is invaluable for night shooting and can be used in most instances where a full tripod can with practice.

Always try to have a secure camera because lower light exacerbates movement and noise on the sensor.

The point is, every shot has a different BEST setting depending on light, your composition and subject.

Best ISO and shutter speed for daylight

Creating an landscape image that has tons of visual impact requires a lot of moving parts, but theres one thing in particular that can really help improve your images.