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Forensics Fundamentals – Part One

I have the extraordinary privilege to teach photography to law enforcement and military personnel across the globe. Often, these uniformed service men and women have a basic understanding of operations behind the camera. It’s been my experience that most take pictures in full-auto mode. Therefore, I start all of my classes with photography fundamentals: ISO, f/stop, shutter speed. I don’t mean to insult anyone’s intelligence, but it’s best to start from the beginning. After all I want them to be the best and feel confident, since their work may be used to solve or prove a crime.

Crime scene investigators learn the fundamentals of exposure during the basic photography refresher course. Photo by Trish Barini

Students are asked to bring their work-issued camera kits and accessories to the class, so they may train with the gear they’ll be using in the field. Gear kits vary dramatically from place to place, so I provide a minimal-gear-requirements list prior to the first day of class, which allows them time to acquire any missing elements. The required gear list includes: camera body, macro lens, zoom lens (example: 24-70), tripod, hotshoe flash, flashlight, basic scale and ruler kit, pen and notepad.

A stack of tripods are made available for students who do not have one in their kits. Photo by Stacy Pearsall

As crime scene investigators, they’ll also have the basic non-photographic necessities such as, but not limited to: hazmat suit or coveralls, rubber gloves, goggles, blood collection kit, bloodstain pattern documentation kit, excavation kit, fingerprint kit, impression kit, print-lifter kit, trace evidence collection kit, body fluid collection kit, trajectory kit, bindle paper, biohazard containment kits, consent/search forms, crime scene tape, chemical lights or flares, tweezers, knife and scissors, magnifying glass, nail clippers, gunshot residue kit, basic tool kit and a first aid kit.

Of course, I also provide additionally recommended photo-related equipment to acquire later. That list includes: Spring Clamp with flash shoe, Lumimuse LED light(s), hotshoe flash modifier, ring flash, gray card, shutter release system, full scale, ruler and marker kit, magnetic rulers, alternate light lens filters, photo fog, camera maintenance kit, weather kit, normal prime lens, wide angle zoom lens, collapsible black background system, background support system, light stand with boom, top hinge black flag, off-camera LED panel(s), LED panel light modifier, Gaffer Tape, polarizing filter(s), photo tent kit, Lastolite TriFlip kit and the list goes on.

Students learn to make manual exposures so they may better understand the functionality of their cameras. Photo by Trish Barini

On the first day of class, I begin with camera review. Most cameras come out-of-the-box with default settings that aren’t conducive to forensics work, so I take them through the various menu settings and function buttons to customize their kits for their needs. For instance, we change the Color Space from sRGB to Adobe RGB, we switch from Matrix Metering Mode to Center Weighted Metering Mode, we move from Auto Area Focus Mode to Single Point of Focus Mode, we adjust the viewfinder diopter for their vision, we set the Exposure and Focus Lock function button to only lock exposure, we review the White Balance function button and more.

From there, I discuss the fundamentals of exposure. To ensure each student understands ISO, f/stop, shutter speed and light metering, I teach the class how to make an exposure in Manual Exposure Mode. I take them into a range of light and ask them to take pictures. The hands-on application and instruction is critical.

Everyone learns differently. For instance, I have to go through the motions and try it myself to really retain the information while others can read it and comprehend it. I try to marry both in my instruction for the benefit of all attending.

Students learn to make manual exposures to better understand the functionality of their cameras. Photo by Trish Barini

By shooting in Manual Exposure Mode, students learn the problem solving skills needed for choosing the appropriate ISO, setting the f/stop needed for their desired depth-of-field and metering the light accurately to determine their shutter speed. Upon completing that instruction, I move them into the semi-automatic exposure modes – most importantly Aperture Priority Mode.

There’s an appropriate exposure mode for every eventuality, but I’ve found that Aperture Priority Mode is versatile enough to handle most cases. By using Aperture Priority Mode, the students still choose their ISO based on the ambient light and decide on their aperture depending on their desired depth-of-field and the camera determines the shutter speed. It just takes one less step out of the human-error equation, but still allows more control over full-auto modes.

While covering Aperture Priority Mode, we review and test the Exposure Lock function button, as well as Exposure Compensation. And, since no one likes to spend hours listening to classroom instruction, we take a photo-walk-about to practice what we’ve studied.

I’m a proponent of the “whistle while you work” mentality. If you’re having fun, it’s not work. Therefore, I spend a bit of time talking about composition, pre-visualization and creativity. I encourage them to photograph fun things they enjoy outside of work, to keep the information they’ve learned during class fresh in their minds. If you practice, it becomes muscle memory.

Students are asked to take a series of photographs in varied f/stops to illustrate depths-of-field and equivalent exposure. Photo by Trish Barini

Once back in the classroom, I go over lenses, lens speed and the lens’ impact on exposure and depth-of-field. We then turn our attention to low-light photography and its challenges. Auto Focus can be a bear in dark settings; I spend time discussing assorted techniques to overcome the aggravating in-out, in-out, in-out of the lens focus mechanism when there isn’t enough light or contrast for the Auto Focus to work. Some cameras have a pre-focus light that illuminates the subject matter and allows the autofocus to hone in and fine focus. Some cameras are not equipped with this technology.

I discuss and demonstrate using a supplemental continuous light such as a flashlight or hotshoe LED such as the Lumimuse LED light to illuminate the subject or the alternative of focusing in Manual Focus Mode. By using an Lumimuse LED light mounted on a Spring Clamp with flash shoe on a for instance, you can set or clip the light near the object your photographing. The light provided is powerful enough to lock focus and shoot.

A demonstration of using a Lumimuse LED light mounted on a Spring Clamp with flash shoe to illuminate and focus on evidence. Photo by Stacy Pearsall

The same technique can be done with a high-powered flashlight. You have to hold your camera and your flashlight, but it’s doable – I’ve got a nifty trick I teach them for just such an occasion.

A demonstration of low-light focus with a flashlight in the classroom. Photo by Trish Barini

I ask the students to flip from Auto Focus to Manual Focus Mode while sitting at their desks. I demonstrate where the Live View Mode button is and ask them to press it. In Live View Mode, I exhibit how to fine focus on an object in front of them. As a little tip, I show them the Live View: Preview Zoom function button that allows them to zoom the display (not the lens) into the object they’re focusing, thus ensuring tack-sharp manual focus.

Only after they accomplish these techniques with the lights on in the room do I dim the lights and challenge the students to focus on a small object using one of the aforementioned techniques.

That exercise transitions us into the next segment, which is supplemental light on a large scale. Since they cannot predict or control where the crime scene will be, they’re often faced with ambient light challenges. Some places may be inside without electricity. Therefore, they need to have the tools to overcome such scenarios.

I take them to a room with no windows where I’ve set up a simulated crime scene. I challenge the students to create an “establishing” or “overall” image of the scene. Most turn to their built-in pop-up flash to illuminate the room. Once they see the results, they know it won’t suffice. I explain how light “falls off” as it travels, aka The Inverse Square Law, and how the size of the light source matters. I tell them they can force more light output by using the Flash Compensation function on their cameras, but even then it’s often still not enough light.

 

The demonstration of using a Speedlight. Photo by Trish Barini

That’s when I turn to my Speedlight, which is a much more powerful flash source. I explain and demonstrate the benefits of having such a flash, or multiples, in their kits. However, since most of them don’t have a flash like mine yet, I show them another technique. I ask the students to stand in a line in the back of the room and place their cameras on tripod.

Students are arranged in a line with their cameras on tripods for a painting with light exercise. Photo by Trish Barini

While the lights are still turned on, I teach them the procedure of painting with light. Since the students do not have shutter release cables, I ask them to switch on their camera’s shutter release to Self-Timer. The reason for using the timer is to reduce any camera shake their fingers may cause upon pressing the shutter release button. During long exposures they don’t want any vibration, as it will appear in the final image.

Then I ask them to switch their cameras to Manual Exposure Mode and Manual Focus Mode. Using a high-powered flashlight or Lumimuse LED light, I ask them to use the Live View Mode manual focus technique. I have them set their ISO to 100, f/stop to 5.6 and shutter speed to 6 seconds (indicated by number six and “ symbol). Most of them questioned the contradiction of ISO theory of less light equals higher ISO to which I explain that they’re providing their own sufficient light over a longer duration of time. In doing so, the light equates to daylight. Therefore, if you’re bringing your own sun you should adjust your ISO accordingly.

I illustrate how to dance the light’s beam around the room and keeping a consistent movement throughout the six seconds of exposure time – making note not to step in front of the camera in the process.

Example of an overall image shot in complete darkness using a built-in pop up flash on the camera. Photo by Stacy Pearsall
Example of an overall image shot in complete darkness with a high-powered flashlight. Photo by Stacy Pearsall
Example of an overall image shot in complete darkness using the painting with light technique. Photo by Stacy Pearsall

From there, we turn off them room’s lights and begin the painting with light exercise. Each student has his or her chance to experiment lighting the reproduction crime scene using this handy technique.

Students conduct a painting with light exercise. Photo by Trish Barini

It’s only after all of the photography essentials are covered that I turn to crime scene photographic coverage and image capture procedures. The fundamental photography foundations must be laid in order to achieve success thereafter.

A macro image of a finger print on a mirror. Photo by Stacy Pearsall

Be sure to check out Part two of Forensics Fundamentals in which I cover macro photography, lighting glass and mirrors and working a crime scene.

Vitec Group