I was talking with a fellow D5100 owner over on my Facebook page and he was wondering why his shots were so dark even though the room had decent lighting. I thought it would be beneficial to share our conversation with all of you...
Mark's Question: Moose, I recently bought a Nikon D5100 (came with the 18-55mm AF-S lens) and a Manual Focus 1:1.8 Nikon Series E lens. I have to use the lens in manual mode. While at my house the first night I tried my camera, I put on the 1.8 to try it out. I could not figure out how to get the pictures to not be so dark. The room had decent lighting so that wasn't the problem. Too much ISO gave it too much grain. I had the aperture all the way open on the lens. What can I do to make this lens work for me?
Moose's Answer: As you've already experienced, cameras see light very differently than what we can see with our eyes. A common misconception is that "bright" lenses (lenses that can obtain apertures between f/1.4 and f/2.8) can somehow magically increase the brightness of a room, however, this isn't the case. While they DO allow more light into the camera, they can't turn up the amount of ambient light available. So for example, if you mount your 50mm f/1.8 lens to your D5100 and look through the viewfinder, the image displayed will look exactly the same as one displayed with the 18-55mm lens.
The key difference between the two lenses is the ability to freeze moving subjects in low light. Let's say your ISO was set to 100. The 50mm f/1.8 would give you a faster shutter speeds than the 18-55mm kit lens. If you're shooting portraits and group shots indoors, faster shutter speeds are critical for eliminating subject blur.
Have I lost you yet? Hang in there ;)
In order to "turn up" the brightness in your shots you can:
1. Use slower shutter speeds, however, you won't be able to stop subject movement and the D5100 will need to be mounted to a tripod.
2. Turn up the amount of ambient light in the room. If you've got one light on in the corner of a large room, it simply won't be enough to get the "bright" shots that you're after. Turn on as many lights as possible.
3. Mount a speedlight like the SB-400 and point the flash head towards the ceiling. By bouncing the light off the ceiling, you'll get nice even coverage throughout the room giving you more natural looking shots indoors. In addition to all of that, you'll be able to obtain fast shutter speeds at lower ISO's.
As for settings, I would shoot in Aperture priority (A on the mode dial) and set your ISO to Auto. Select apertures between f/1.8 and f/2.8 for portraits and f/4 to f/5.6 for group shots.