Often, evidence is stored in plastic bags or containers with shiny surfaces that result in reflective glare when photographed. This glare can obscure both the content and any markings on the bag or container.
As an example, a small piece of the bead toe from a tire was placed in a plastic bag, which was labeled with a black magic marker. (The writing on the bags in the images below has been intentionally altered to preserve anonymity.)
This first image was made in my Studio Lab using just the overhead LED lights. [Click on image to enlarge, then click on left arrow to return to this post.]
Plastic Evidence Bag without Flashes (Made with ZEISS Milvus 50 mm f/2 Macro lens on Nikon D850 at f/16, 1 sec, ISO 64.)
Even though the image is properly exposed, the overhead LED lights resulted in so much glare that it is difficult to make out the tiny tire piece inside or the writing on the outside of the bag.
To show both the contents and the writing, I kept the overhead LED lights on, but added a Profoto B1x studio flash on the right and on the left side of the bag. (Note: any remote flashes or speedlights can be used for the same effect.) [Click on image to enlarge, then click on left arrow to return to this post.]
Plastic Evidence Bag with Flashes (Made with ZEISS Milvus 50 mm f/2 Macro lens on Nikon D850 at f/16, 1/200 sec, ISO 64. One Profoto B1x strobe to each side triggered by a Godox TT685N II flash in the camera’s hot shoe.)
Wait, how did adding even more light eliminate the glare? Two things combined to make that work.
First, the added light from the flashes allowed me to significantly reduce the overall exposure. In this case, for both images I kept the aperture at f/16 for depth of field, and the ISO at 64 for lowest noise/highest dynamic range.
In the original image using the overhead LED lights only, the shutter speed was 1 second. When I added the flashes, I reduced the shutter speed down to 1/200 second. This faster shutter speed prevented the overhead LED lights—and their reflections—from recording at all. If I turned off the flashes, the image would have been black, even though the overhead LED lights were on.
Second, the light that reflected from each flash bounced away from its respective flash, and not into the camera lens. Hence, their reflections were not recorded by the camera.
Takeaways:
-1- To reduce or eliminate glare from overhead lights, reduce the exposure enough to cause the image to go black, or nearly so.
-2- Add one or more flashes positioned (usually to the sides) such that any reflections bounce away from the lens, not into it.
-3- Adjust the power of the flash(es) to properly light the subject at the new exposure.
-4- Note: With curved or irregularly shaped objects (like plastic bags), some localized reflections may remain. These may or may not be moved or eliminated by changing the positions of the camera or the flash(es).
When your subject has multiple similar features, you’ll need to mark each of them to distinguish among them in your photographs. These markings must be repeated on the other side of your subject, too, if applicable.
Since you are dealing with evidence, you should never make permanent marks unless agreed to by all parties involved beforehand. Instead, it’s best to use removable stickers or labels.
Before applying any labels, photograph the subject as you received it. This will ensure no part of the evidence is masked. As an example, here is a photograph of the mounting surface of an eight-bolt wheel with sixteen holes so it can be used with more than one bolt circle. (Click on image to enlarge, then click on the back arrow to return to this post.)
Nikon D850 with ZEISS Milvus 50 mm macro lens and Nikon R1C1 macro flashes. f/16, 1/200 sec, ISO 64.
Using a Brother P-touch labeler, I made one long label with two strings of numbers from 1 through 8, then cut between each number to create small labels of each individual number. The goal was to make the labels as small—yet as legible—as possible so they would mask the least amount of the evidence.
Choose a font with legible numbers, and set the font style to bold. Depending on the color of evidence, I usually use either white on black or black on white labels. On rare occasions, I have used black on clear labels. It’s advantageous to have all three label tapes available.
A label maker creates labels that are more legible and more professional looking than writing numbers by hand on torn pieces of tape.
For this wheel, I numbered the holes in pairs. Note that the numbers are counterclockwise on the inside so they will correspond with the same numbers on the outside of the wheel, which were clockwise. (Click on image to enlarge, then click on the back arrow to return to this post.)
Nikon D850 with ZEISS Milvus 50 mm macro lens and Nikon R1C1 macro flashes. f/16, 1/200 sec, ISO 64.
Here is the outside of the wheel showing the clockwise bolt hole pair labels. (Click on image to enlarge, then click on the back arrow to return to this post.)
Nikon D850 with ZEISS Milvus 50 mm macro lens with two Profoto B1x in diffused silver umbrellas. f/16, 1/200 sec, ISO 64.
Now close-ups of every hole will be easily identified whether on the inside…
Nikon D850 with ZEISS Milvus 100 mm macro lens and Nikon R1C1 macro flashes. f/16, 1/200 sec, ISO 64.
…or the outside of the wheel. Note that the labels are a good size in the close-ups without overwhelming the subject. Also note that the label is still effective even if it is out of the depth of field of the subject and is slightly out of focus.
Nikon D850 with Laowa 24mm f/14 2X Macro Probe. f/unrecorded, 0.5 sec, ISO 64.
Takeaways:
-1- After photographing evidence as found or received, mark repetitive features on any sides that will be photographed.
-2- Do not make permanent marks on evidence.
-3- Mark evidence with small, legible, and removable labels instead of handwritten numbers on torn pieces of tape.
-4- While labels should be included in close-ups, they do not have to be within the depth of field of the subject as long as they are still discernible.
-5- After making each close-up image with its label, you may want to remove the label and take another photograph without it. Having your camera on a tripod will allow you to made identical shots both with and without the label.
Perspective is the relationship between the elements in your photograph. The only way to change perspective is to move the camera. In fact, any time you move the camera, your perspective automatically changes. Conversely, staying in one place and zooming in or out doesn’t change perspective; it only crops the image differently.
This series of photographs demonstrates perspective change by using a 24-70 mm zoom lens and changing the camera position while using four increasingly long focal lengths: 24, 35, 50, and 70 mm . All were made from my standing eye height. The goal was to keep the subject car the same size in each image by moving the camera further away at each longer focal length.
When the resulting images are viewed at the same distance, you’ll note two effects from increasing camera distances while using longer focal lengths: -1- the car appears to change shape and compress, and -2- the background and other vehicles seem to be getting closer to the subject car.
This spectacular 1937 Cord Model 812 Beverly Sedan was photographed at the Savoy Automobile Museum in Cartersville, GA. Like most car museums, neither tripods nor flash are allowed. This requires using high ISO and slow shutter speeds to obtain your images. Fortunately, almost all full frame and some cropped sensor mirrorless cameras have amazingly effective in-body stabilization, which allows handholding the camera at low (slow) shutter speeds that were almost impossible before.
While these examples were made at a car museum, the principles apply exactly the same for any vehicle—or any subject—anywhere.
For this first image—made with a 24 mm focal length—I was quite close to the car. Note how long the hood looks and how far away the DeLorean and the background appear. [Click on image to enlarge, then click back arrow to return to post.]
Made at Savoy Automobile Museum, Cartersville, GA, using handheld Nikon Z 7II with 24-70 mm f/2.8 lens at 24 mm. Exposure: f/9, 1/30 sec, ISO 1600.
Stepping backward with a 35 mm focal length, the Cord looks less distorted, and the background vehicles seem closer. Of course, no vehicles were moved between any of these images. [Click on image to enlarge, then click back arrow to return to post.]
Made at Savoy Automobile Museum, Cartersville, GA, using handheld Nikon Z 7II with 24-70 mm f/2.8 lens at 35 mm. Exposure: f/9, 1/30 sec, ISO 1600.
Moving further away using a 50 mm focal length appears to once again shorten the hood and wheelbase of the Cord, while bringing the background even closer. [Click on image to enlarge, then click back arrow to return to post.]
Made at Savoy Automobile Museum, Cartersville, GA, using handheld Nikon Z 7II with 24-70 mm f/2.8 lens at 50 mm. Exposure: f/9, 1/30 sec, ISO 1600.
Back even further with a 70 mm focal length apparently compresses the Cord even more and brings the DeLorean and background closest yet. [Click on image to enlarge, then click back arrow to return to post.]
Made at Savoy Automobile Museum, Cartersville, GA, using handheld Nikon Z 7II with 24-70 mm f/2.8 lens at 70 mm. Exposure: f/9, 1/30 sec, ISO 1600.
Takeaways:
-1- When you move your camera, the perspective of your resulting image changes.
-2- When viewing images from the same distance, moving your camera closer to your subject with a wider focal length makes your subject appear distorted and your background objects farther apart.
-3- Again, when viewing images from the same distance, moving your camera farther away from your subject with a longer focal length makes both your subject and background elements to appear more compressed.
Although the effect is usually unintentional, a single image may be deceptive!
In the photograph below, both the height and the angle of the camera seem to indicate that the subject SUV was a two-door model. But actually, there was no such vehicle as a two-door 2004 Chevrolet Trailblazer. In fact, the subject shown here was even the extended EXT version of the standard four-door. (Note the top of the chopped off B-pillar visible above the window frame, which is the clear giveaway that it is actually a four-door SUV.) [Click on image to enlarge, then click back arrow to return to post.]
2004 Chevrolet Trailblazer EXT LT 4WD 3/4 side view. (Nikon D850 with ZEISS Milvus 50 mm f/2 macro lens with polarizer, fill flash, and tripod. f/13, 1/40 sec, ISO 125.)
It is standard practice to make multiple photographs around every subject vehicle. It’s also often necessary to make images at different heights and angles. No one who sees all of our photographs will be deceived. The problem is when you get only one or maybe a couple photos of a subject you either haven’t or can’t inspect yourself.
Using the same prime ZEISS 50 mm lens at the same tripod height, the photo below clearly shows the vehicle was a four-door. [Click on image to enlarge, then click back arrow to return to post.]
2004 Chevrolet Trailblazer EXT LT 4WD side view. (Nikon D850 with ZEISS Milvus 50 mm f/2 macro lens with polarizer, fill flash, and tripod. f/13, 1/30 sec, ISO 125.)
This unintended deception isn’t an issue when you’re making your own photographs, but it can be a problem if you’re trying draw conclusions based on a limited number of photographs provided to you. This frequently happens when the vehicle has been destroyed or is otherwise unavailable, and only one or a couple photographs—often made with a cell phone—are all the evidence that remains.
Takeaways:
-1- Be careful making conclusions based on a single photograph.
-2- Make a series of images around the entire circumference of any vehicle or subject you are documenting.
Thanks to Matt Wasowski of SAE for putting together such an excellent digital accident reconstruction conference, and thanks, Matt, for allowing me to present. Thanks to all those who attended, too. Sorry about my abrupt exit; it was a technical glitch on my end.
As promised, here are the slides from my talk: Tom Vadnais Photography SAE Presentation_2022-03-30. Bonus: You’ll see there are some additional slides that I had to remove from the talk to get it to fit the alloted time. No additional charge for those extras! Ha, ha.
Please don’t hesitate to call or e-mail if you have any questions about what we covered or about my upcoming SAE class. I hope I get to meet you personally at my class July 12-14, 2022, at Mecanica Scientific Services in Oxnard, CA.
With live classes now returning to SAE, I’m excited to announce that my next Photography for Accident Reconstruction, Product Liability, and Testing class will be July 12-14, 2022 at Mecanica Scientific Services’s fantastic classroom facilities in Oxnard, CA. Special thanks to Mecanica’s John Steiner for hosting this class for the third time!
The class has ten major subject modules that build upon each other. We’ll explore in-depth about gear, light, camera fundamentals, settings, post-processing, and much, much more. You’ll come away not just knowing about, but actually understanding how to make better, more consistent, and more useful photographs during all your inspections and analyses, regardless of lighting conditions.
Please call or e-mail me directly if you have any questions or need more information.
SAE International is hosting a FREE Accident Reconstruction Digital Summit on March 29 and 30, 2022. There will be presentations on a wide variety of current issues and areas of interest to anyone working in or with accident reconstructionists, including law enforcement, engineers, attorneys, and insurance adjusters.
From 1:45 to 2:15 pm EDT on Wednesday, March 30, I’ll be presenting on the importance of using a tripod, a polarizer, and a flash during inspections in the field, in storage facilities, and in the lab. The use of those tools can result in superior images—in the camera—with detail and data you can’t extract or replicate later in post-production. Best of all, you can put those three tools to work immediately, which will make your photographs consistently better and more useful.
By the way, my presentation will be just a snippet of what we’ll cover in my three-day SAE Forensic Photography class. Now that SAE will be resuming in-person classes this summer, I’ll post the next class dates as soon as they are finalized.
Eugene Liscio, 3D Forensic Analyst and founder of ai2-3D, has assembled the first virtual Forensic Photography Symposium to be held January 17-20, 2022. There are many intriguing and helpful sessions each day with ideas and solutions to many problems often encountered in many areas of forensic photography. Here’s a link to the schedule and registration: Forensic Photography Symposium Schedule & Registration
I’ve been honored to have been asked by Eugene to present a session on the three most essential photography tools besides your camera and lens. They are: tripods, polarizer filters, and flashes. Most forensic photographers know what those tools are, but this presentation is designed to explore and show examples of how their regular use can drastically improve the quality and usefulness of your images. Using these tools, you will be able to consistently capture and present more data in each of your images, which is the whole point of making forensic photographs!
Screenshot from YouTube Intro for Forensic Photography Symposium January 17-20, 2022.
While this is hardly news, on sunny or lightly overcast days, the positions and sizes of the shadows of trees, buildings, signs, poles, fences, guardrails, etc., change throughout the day. At certain times, these shadows can make it difficult to clearly show tire marks, paint marks, or gouges in your photographs. The worst is when there is a pattern of light and shadow across your scene.
This first image was made at 10:21 am on a mostly sunny morning. (Click on image to enlarge. Then click back arrow to return to this post.)
Tree shadows at 10:21 am on 09/04/21. (Made with ZEISS 50 mm f/2 macro lens on Nikon D850 on RRS TFC-24L tripod with BH-40 ball head. f/11, 1/8 sec, ISO 64.)
This view was made looking south, so the morning sun would have been to left, or east. The dense line of trees on the eastern edge of the road cast a shadow across the entire road with bright spots through the openings in the branches. These bright spots can interfere with details or evidence you might want to show.
Returning to that same scene at 2:45 pm that afternoon, the overcast had burned off. Even though the sun was quite bright, it was at an angle that evenly illuminated a lot more of the road, with only some shadows at the left. (Click on image to enlarge. Then click back arrow to return to this post.)
Tree shadows at 2:44 pm on 09/04/21. (Made with ZEISS 50 mm f/2 macro lens on Nikon D850 on RRS TFC-24L tripod with BH-40 ball head. f/11, 1/60 sec, ISO 64.)
By late afternoon that day, it had become too overcast for deep shadows, so I went back a couple afternoons later to capture what that scene would look like later on a sunny day. The image below was made at 6:52 pm. (Click on image to enlarge. Then click back arrow to return to this post.)
Tree shadows at 6:52 pm on 09/09/21. (Made with ZEISS 50 mm f/2 macro lens on Nikon D850 on RRS TFC-24L tripod with BH-40 ball head. f/11, 1/15 sec, ISO 64.)
Those seemingly innocuous trees to the west (right of the photo) were now casting long, separated shadows across the road. These shadows would obviously make it more difficult to show gouges, tire marks, or even paint marks on the pavement.
Time permitting (i.e., it’s not a rapid response), it’s worth checking out where the sun and any shadows would be before you set out to inspect a scene.
For many years, I’ve been using The Photographer’s Ephemeris (TPE) https://photoephemeris.com/en to determine where the sun is going to be in relation to any accident site. (It’s now a subscription service, and well worth the small cost.) It’s extremely valuable if you need to show whether the sun could have been in the eyes of any drivers or witnesses.
And as in this case, it’s also useful for determining when you have the best chance of getting clean site images with minimal shadows. Below are the three TPE screen captures that show what information you get.
The first shows where the sun was when the 10:21 am photo (top one above) was made. (Click on image to enlarge. Then click back arrow to return to this post.)
TPE 10:21 am on 09/04/21.
The line of the sun is shown as the narrow gold line coming in from the lower right toward the pin marking where my tripod had been set up. Note that while the photographs were made looking south, the TPE diagrams have north at the top. So the morning sun in the east will be from the left side in the photos and from the right side in the TPE diagrams. (Just FYI, the wider yellow line at the upper right was the sunrise angle while the wider orange line at the left was the sunset angle.)
This diagram showed that at 10:21 am on 09/04/21, the sun would have been coming in from the eastern side of the road through a thick area of trees, which is exactly what was shown in the top photograph.
At 2:45 pm on the same day, the sun was beyond the thick trees to the east, yet below the tree line to the west. This should result in a photograph with minimal shadows on the road, as the second photo above shows. (Click on image to enlarge. Then click back arrow to return to this post.)
TPE 2:45 pm on 09/04/21.
When I went back a couple days later at 6:52 pm, the TPE diagram showed that the sun would now be far enough west that it would come through the line of single trees to the west once the sun got low enough in the sky. Once again, that is precisely what the third photo above illustrates. (Click on image to enlarge. Then click back arrow to return to this post.)
TPE 6:52 pm on 09/09/21.
TPE gives both the azimuth and altitude of the sun. In this post, I’m only using the azimuth for direction, and applying a general knowledge of how high the sun will be from experience. For a question about whether the sun was in a driver’s eye, you’ll have to use both azimuth and altitude. That’s a future post.
TPE has many more sophisticated applications, including using AI to show where the sun or moon will be in a scene. It’s well worth getting and exploring all of its features. (I have no ties to TPE nor receive any compensation from them. It’s just a great tool I highly recommend.)
Takeaways:
-1- Before you photograph your wreck site, it’s often worth determining when the sun will cause the fewest or shortest shadows on your road.
-2- The Photographer’s Ephemeris is well worth using when you need to know where the sun will be at specific times on specific dates.
It is essential to keep truck tires properly inflated so they can carry the load, wear evenly, maximize fuel mileage, and maintain their integrity. Chronic overdeflection (overinflation, underinflation, or a combination) is a common cause or contributor to tire failures.
During pre-trip inspections, the Federal Motor Carrier Safety Regulations (49 CFR §396.13) requires the driver “be satisfied that the motor vehicle is in safe operating condition.” This includes the truck’s tires . As part of that pre-trip tire inspection, a driver is trained to look for low or flat tires. But there is no requirement that the driver check the air pressure with a gauge. In fact, while going through truck driving school before getting my CDL, we never once used an air pressure gauge during our pre-trip inspection lessons, daily routines, or exams.
It would be an onerous task to require a driver to check the air pressure of all eighteen tires on a typical tractor trailer before every trip. As an alternative to a gauge, some drivers use a “tire thumper” (usually a rubber mallet or some kind of a bat) to check their tires. If a tire is inflated, the thumper would bounce right off. Striking a tire with little or no air would have no bounce back, but would respond with a flat thud. While a thumper can’t determine if a tire is properly inflated, it can let you know if a tire is flat or near flat. [Click on image to enlarge, then click back arrow to return to this post.]
Only the bottom four of these will give you an accurate truck tire inflation pressure. (Made with ZEISS Milvus 50 mm f/2 Macro lens on Nikon D850 at f/16, 1/200 sec, ISO 64. Used one Profoto B1x studio strobe with silver umbrella with diffuser on each side.)
Back in 1998, I bought the Trucker’s Toothpick & Tire Tester at the top of the photo at a truck stop just for fun. (Both the name of the product and the company are rather whimsical.) It is a weighted metal stick with a hand grip on one end and a protective cover on the other. Along with various wooden bats, it is typical of tire thumpers sold commercially. While their benefits are minimal, at least thumpers prevent a driver from starting off on a trip with a flat tire.
The three stick gauges in the middle of the photo look similar, but their dual heads are at different angles. One of them is bound to fit when the metal valve stems of either the inner or outer tire of a dual pair are bent and otherwise inaccessible. They prevent you from bleeding air out of the tire as you try to get the gauge head to seat on the valve.
Stick gauges seem tricky to read until you understand how their scale works. I’ll describe that below.
The digital pressure gauge at the bottom is the easiest to read (and photograph, if you do that—I don’t).
Here’s how to read a truck tire stick gauge. Assume you’ve just checked the air pressure of a steer axle tire and got the reading below. [Click on image to enlarge, then click back arrow to return to this post.]
Scale on truck tire inflation pressure gauge. (Made with Nikon 105 mm Micro lens on Nikon D850 at f/16, 1/200 sec, ISO 64. Used one Profoto B1x studio strobe with silver umbrella with diffuser on each side.)
At first glance, the scale might not seem to make sense with the decimals between the longest hash marks. (Gauges typically start at 10 psi, not 0 psi; anything less than 10 psi is obviously flat.)
Zooming in might help make deciphering the scale more clear. (This photo has been rotated clockwise to be oriented as you would read the scale in use.) [Click on image to enlarge, then click back arrow to return to this post.]
Rotated close-up of scale on truck tire inflation pressure gauge.(Made with Nikon 105 mm Micro lens on Nikon D850 at f/16, 1/200 sec, ISO 64. Used one Profoto B1x studio strobe with silver umbrella with diffuser on each side.)
Let’s start with the 100 psi mark. (Note that on this gauge, the 100 psi hash mark happens to intersect the second zero.) The next short hash mark down represents 102 psi. One shorter hash mark down is 104 psi. Just below that, the longer hash mark near the center of the scale represents 105 psi. The next short hash mark at the right edge below that is 106 psi. Below that, the short hash mark is 108 psi. Next is the longer hash mark for 110 psi. Using this information, you can see the inflation pressure reading above was 118 psi.
To summarize, all the hash marks along the right edge of the scale are in 2 psi increments. Half way between the decimals, the longer hash marks near the center of the scale are in 5 psi increments.
Anywhere along the scale, anytime the end of the barrel is halfway between two consecutive short hash marks, the inflation pressure is 1 psi greater than the short hash mark above it.
Takeaways:
-1- While truck tires must be properly inflated, the Federal Motor Carrier Safety Regulations do not require truck drivers to check tire inflation pressures with a gauge during their pre-trip inspections.
-2- Tire thumpers can indicate if a tire is flat or almost flat, but cannot determine the inflation pressure.
-3- Different angles of dual head inflation pressure gauges can help access bent valve stems.
-4- If using a stick gauge, make sure you accurately read the scale.
