Friday, June 5, 2009

Mini-Tutorial: Crime Scene Photography

Painting With Light

When it comes to crime scene photography in low light, small portable speedlight flash units are a crime scene photographer's best friend.

Today's electronic flash units are smarter, more adjustable, and more powerful than ever. They can handle a myriad of lighting conditions from a small wink of light to fill shadows, to a full power burst to fill a room with light.

The majority of indoor and night time outdoor crime scenes can be photographed with little to no trouble once you have mastered a few techniques. A good working knowledge of your camera and flash unit's exposure compensation controls will help you tune your on-camera flash photographs to the correct exposure. A time exposure, leaving your camera's shutter open for an extended period of time while your camera is on a tripod, or a shutter-drag, a flash photograph with a slower then normal shutter speed, can be very effective ways to capture a scene in a low available light situation.

But what do you do when you have a large scene with very limited to no available light; a scene much larger than a single burst from your flash can illuminate and that has almost no other light to use for a time exposure? You can utilize a technique known as Painting with Light.

Simply put, painting with light involves using your camera on a tripod, opening your camera's shutter, and using your off-camera flash unit to "paint in" light by firing it manually, multiple times throughout your scene.

To demonstrate this technique, I took a number of photographs of a large area of a park with very little available light.

The first photograph was taken well after sunset with the lens aperture wide open and the flash unit on-camera, set at full power.

The flash illuminates the foreground but quickly falls off to what I like to call "the black hole effect". There is simply not enough power in a speedlight flash unit to light a scene of this size with a standard on-camera flash exposure.

Now for the fun part. In order to demonstrate the painting with light technique, I predetermined fifteen spots throughout the scene from which the flash would be fired after sunset. Before the sun went down, I photographed my assistant at each of these locations and compiled the images into the following slide show.

The slide show demonstrates the location of each place the off-camera flash will be manually fired during a long exposure once darkness has fallen.

Movement of the camera during the long exposure must be avoided, so use a sturdy tripod to steady your camera. Most Digital SLR Cameras will allow exposures up to thirty seconds in the manual mode. The problem is, thirty seconds is often not enough time to paint a large scene with multiple bursts from your strobe.

That's where your camera's Bulb setting comes in. The Bulb setting usually appears right after 30 seconds when you are setting your shutter speed in the manual mode. When your shutter speed is set to Bulb, the shutter will open when the shutter release is depressed, and will remain open as long as you keep it depressed. One minute, one hour, as long as you keep the shutter release depressed, the shutter will remain open, exposing your sensor to light. Pretty cool huh? You always wondered what that odd little setting was for didn't you?

Obviously you can't keep your camera steady while depressing the shutter release for an extended time. Depending on your camera model you can use a conventional shutter release cable that manually locks the shutter release open, or a wired or wireless electronic shutter release that accomplishes the same thing.

Depending on your depth-of-field needs, set your fstop near wide open. To keep noise under control, I usually keep my ISO setting in the 400 to 800 range.

Setting your focus to manual will keep your auto focus from trying in vain to lock focus in the dark. Use your flashlight to help focus on your scene and to make your camera adjustments.

The idea is to blanket your scene with bursts from your hand-held strobe unit as evenly as possible. Emphasis should be put on illuminating areas with evidence, markers, etc.. Easier said than done right? It does take some practice, but with a little trial and error, you will get good exposures of your scenes that were nearly impossible to get with on-camera strobe exposures.

Here is the final result of fifteen pops of the strobe during an approximately two and a half minute exposure.

Perfect? No, but so much better than the original on-camera single flash exposure.

Experiment with this technique before photographing an actual scene. Try using two people with two strobes if you have the resources. Use the lights of your vehicle to illuminate areas of your scene. Always have new batteries in your strobe or use an external battery for faster recycle times. You are only limited by your creativity.

Here are a few things to avoid: Don't get between the lens of your camera and the strobe when you pop the flash. The result will be a ghost-like image of you in the photograph.

Make sure your strobe is always pointed into the scene and not back toward your camera. The result will be a star burst effect if you allow your camera to see the front of your flash.

The more you paint with light, the more comfortable you will become with this great technique.


  1. Greetings-

    Could one accomplish the same thing with multiple flashes and pocket wizards?


  2. Yes Jim. This was fifteen pops from a single flash unit, but with enough strobes and pocket wizards, you could get similar results.