Tuesday, August 30, 2011

Shooting in Low Light Conditions

One of the biggest challenges photographers face is not having enough light. Especially when shooting weddings, concerts, anything indoors...

"You just spent $500 on a fancy digital camera, so why do your pictures of your kid blowing out the candles on her birthday cake look so terrible? The answer is that indoor, low-light photography is not always as simple as point and shoot." 

There are several things one can do when shooting in low light... First, you can always bring in more light. External flash, strobe lighting, reflectors, etc are all ways one could increase the light in an indoor space.

But while using a flash seems to be the obvious answer to low light situations, they have their downsides. Not only does a flash interfere with the "moment"... it also tends to flatten images, distort colors and wash out skin tones. It also tends to provide "uneven" light on and around your subject. This problem is especially true with the cheap, built-in flashes on most compact digital cameras. When using a flash, the best kind to use is an external flash, commonly known as a speedlight. The pro's will tell you to just nix using your pop up flash all together. A speedlight with the capability to rotate or tilt the flash in order to bounce it off the ceiling is a good way to balance the light. Another good use of an external flash is to mount it off camera.

If no "external light source" what do you do? The first thing pros will suggest is to ratchet up your camera's ISO or "light sensitivity" setting. Traditionally, high speed film (ISO 800 and higher) was better suited for low light photography. Unfortunately, where high speed film produced enlarged grain, which could often be used for artist effect, higher ISOs on digital cameras tend to just produce color noise -- little specks of red green and blue scattered across your image.

Most point and shoot cameras, even those with manual controls, won't produce quality images above 400 ISO. The solution then is to use lower ISO settings, but that means you'll be facing a new concern -- long exposures.

Noise Reduction Software
High ISO setting tend to create unacceptable levels of color noise in the finished image. There are some ways to get rid of color noise after the fact. Photoshop ships with a noise filter which will smooth your pixels by blending surrounding areas together.

Unfortunately, for all but the most basic situations, the results won't bowl you over. Dedicated software like Noise Ninja ($35-$80, depending on the license) can produce much more dramatic improvements with very little blurring or other side effects. It isn't cheap, but if you do a lot of low light photography, it's a godsend.

Overexpose to Reduce Noise

Another way to reduce noise in a photo is to slightly overexpose your image to the right of the histogram (works especially well if shooting in RAW) and adjust the exposure down in post processing.This works okay for low light situations, and the main thing is to only overexpose to the point before you blow out your whites. If you blow out the highlights in the image, you won't be able to get the detail back. Most cameras have a "blowout warning" that will flash on the screen if you are too far overexposed. 

The image below is your histogram. The left image is a normal exposure (the middle of your meter.) The right image is a slight overexposure, but not to the point of blowout.

If you expose to the point of blowing out your highlights your histogram will look like this:

 Reducing Motion Blur

Long exposure times increase the chance you'll blur the shot, whether through the subject's movement or yours. Here are a few tips for blur-free shots:
  • Start with the largest aperture your camera allows. Use aperture-priority mode if you have one and set f-stop down to f/1.8 or the lowest available.
  • Set the ISO higher (and overexpose to reduce noise as described above).
  • If you have a zoom lens, zoom out as much as possible. More light will hit the photo sensor and exposure time will go down.
  • If the exposure time is still greater than what you can handhold, use a tripod, or anything that will keep your camera still.
  • Consider something small like the Gorilla Pod, a small, flexible tripod which will fit nicely in the average coat pocket. There are several sizes available, some of which probably won't fit in your pocket but still aren't as cumbersome as full-size tripod.
  • If you don't like to carry even a tiny tripod with you all the time, don't worry - there are plenty of solid objects that can fill the role. Just hold your camera up to anything that doesn't shake - a lamppost, a tabletop, a wall - and press on it to keep it still while you take the photo.
  • To reduce the shake that results from pressing the shutter button, use the camera's timer function. Most cameras will have a two-second delay timer that works great, especially on long exposures.
If you have a surgeon's hands, you can try hand-holding even long exposures. Pick a solid stance with your legs slightly apart (like two legs of a tripod). Brace the camera against your face and hold your breath while you press the shutter. Be sure to zoom in on the resulting image to check for blurring! 

Balance Your Whites

The next challenge you face in low light situations is the lighting. In most cases you'll be shooting in artificial light -- the chandelier above your dinner table for instance. 

Light temperatures from incandescent bulbs or florescent overheads can cast yellow or blue tones over a scene. Sometimes, this can have a nice warming effect (in the case of incandescent light). But other times it may not be what you're looking for. 

The solution is to adjust the white balance in your camera. Most digital cameras offer a variety of preset white balance settings which you can experiment with. If all else fails you may be able to customize your own settings. Keep in mind that if you're shooting RAW images, you can always change the white balance after the fact using software. 

Timing Is Everything

Here's our general guide to exposure times (assuming the widest aperture possible). You'll need to experiment to see what works for you.
  • Christmas lights: 1/4 to 3 seconds of exposure.
  • Cityscapes: 2 to 30 seconds.
  • For a night sky with star trails, use the formula: exposure = 600s/focal length of the lens in millimeters.

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