I'm a real beginner at photography, but over this past year I've been trying to teach myself little tricks here and there. Currently I want to start trying out night photography. However, despite watching lots and lots of videos on which settings I should put my camera on, once I'm outside the camera can't even begin to show anything. It just says the subject is too dark and shows a completely black image on the screen. I'm sure I'm doing something really basic wrong but I don't know what it is. I have a Nikon d3100 with the kit lens and 50mm lens. Is it something to do with that? Or something else?
despite watching lots and lots of videos
Spend less time watching videos and more time taking photos.
Prepare your settings
1) Define what is your "night" photography. A cityscape, a dark night on a dark forest without any light?
2) Mount the camera on a tripod
3) Set your iso at 800 and manual mode.
4) Open your lens all the way up. If you have your 50mm try using that one. Lets say at f1.8?
Make a bracketing
5) Shoot one photo at 30 seconds. One at 15, 8, 4, 2, 1, 1/2, 1/4.
At some point you will find what iso/aperture/velocity you have a good result.
If you do not have an image at 30 seconds... something else is wrong.
Get a tripod.
This is essentially why the camera says subject too dark. It is a warning normally issues to indicate that the resulting image will be blurred due to the camera moving during the exposure.
Use the optical viewfinder
As long as you can see your subject, you will be able to shoot it. That is what a viewfinder is for. When you use Live-View, the camera has to basically perform an exposure 30 or more times per second to show the preview. However, beyond a point, 1/30s is insufficient to show any details which is why the screen appears black.
Take Longer Exposures
When you take night photographs, exposures will easily reach into the order of several seconds and your camera will let you pre=select up to 30s but do not let that limit stop you. You can take longer exposures of several minutes (even hours on some models) by using Bulb mode.