How to collect digital evidence in inclement weather?

Inclement weather can create interesting challenges for crime scene photography. Whether we’re collecting physical evidence or digital evidence, we do not get to pick our crime scenes but rather our crime scenes pick us based on when they occur and the hours during which we are working.

Foul weather also affects our documentation stage of the scene. Have you ever tried taking photographs in the rain, snow, or fog during nighttime conditions? Your biggest enemy when trying to take pictures in rain, snow, and fog is your flash unit. This is because the light from your flash unit leaves your flash and is reflected back to your lens by each raindrop and/or snowflake and fog. This can be easily dealt with, but it does slow you down. You can minimize the amount of light reflecting back to your lens by going off-camera with your flash unit and using your sync cord. The further your flash unit is off to the side from your camera, the less reflection you will get; however, this is not likely to eliminate the problem, but rather minimize the problem. If you want to eliminate the problem, you have to eliminate the flash unit. This means you have to pull out your tripod. You will need to be familiar with your camera so that you can change some settings away from your standard point and shoot. Find your exposure compensation button and try going plus 3.0 F Stops. This will substantially increase the quantity of light coming in through your lens. You should still have your camera in either “Program” mode or “Aperture Priority” mode.

Camera and Image focus is another challenge, make sure you have gotten a good focus on your camera before actually taking your picture. Manual focus is likely to be your friend here as your camera may find that getting a focal lock in this situation could be difficult without the use of a flashlight for temporary lighting. Once you depress the shutter button, you will find that your shutter will stay open much longer than normal. It may stay open for 30 seconds or more depending on ambient lighting conditions. This is normal and it works toward what you are trying to accomplish. The reason that this helps is that the film plane is exposed to a small amount of light for a long period of time. This makes it so that anything that is moving through the picture, such as rain or snow, will simply disappear as they are not in the frame long enough to be recorded.

The appearance of fog will not disappear, but will at least be minimized. The result will not only be a picture without the reflections of the rain and snow but will also be a photograph that will make it appear as if you took the photo during nearly daytime lighting conditions due to the exposure compensation. The result is that you have taken care of two problems with one photograph. You have turned night into day and stopped the rain or snow. If you want to eliminate the rain or snow but maintain the natural lighting perspective, you can still accomplish this task as well. In this case, do not start with exposure compensation. Instead, only use your “Aperture Priority” setting and set your F-Stop to F16 or similar for a good depth of field. Try taking a picture. This setting should keep your lens open long enough to let the rain and/or snow pass through the picture mostly unnoticed. If the photograph appears darker than actual conditions, just adjust your exposure compensation a little at a time to get the lighting effect that is almost like a natural perspective. If your shutter speed is still too fast at F16 due to ambient light, you can reduce the size of your aperture to F22 or greater depending on your lens capabilities.

Time exposure photography can be used for more than just foul weather. It is a greatly underutilized technique for outdoor nighttime scene photography as well. Flash photography is great for your mid-range and close-up photography but is almost never sufficient to document the overall photos of a scene that has any real size to it. That is where your tripod and exposure compensation again become a go-to technique.

Old school documentation for this type of photography on crime scenes would have necessitated a photo log in which one has to record all of their camera settings so that the methodology behind the photograph can be easily understood and expressed. Now, with modern digital point and shoot and digital SLR cameras, that is done automatically for you as there is all sorts of metadata that are associated with every picture taken. This data is embedded in that photo data itself. This records all the information about the photograph such as date, time, camera model, serial number, F-Stop, shutter speed, flash or no flash, exposure compensation settings, camera mode, etc… This captures way more information than most photographers would have been capturing in a traditional photo log. A good Digital Evidence Management System will be a great friend as it will not only preserve and protect your images and maintain their chain of custody through an unalterable audit trail, the Digital Evidence Management System will also maintain your metadata and present it to you as the consumer of the information in such a way that will be convenient, useful, and easy to search for. Keep in mind, you may be asked to explain how you took a photograph at night, in a dark field, in the rain, and yet the photograph itself appears to be virtually day time as if it is just an overcast day. Make sure to upload all digital photos and videos to your Digital Evidence Management System, including those you don’t think are clear enough. You never know when you’re challenged in court to explain how the last photo you took has the number 49 and you only have 15 photos to show in court.

Be sure to practice these, and any other techniques, you use in mock situations before taking them to the real-world environment. You may find that you will learn at least as much from your failures as you do from your successes, so practice, practice, and then practice some more.

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