SAE International has scheduled my next Photography for Accident Reconstruction, Product Liability, and Testing (C1729) class at their excellent Troy, MI facility from April 4-6, 2023: https://www.sae.org/learn/content/c1729/
It’s a great facility and is quite easy to access on W Big Beaver Rd just off I-75. It’s about 45 minutes from the Detroit airport. There are plenty of hotels and a lot of great restaurants in every price range.
The link above provides a detailed course outline. We’ll also get hands-on time to practice with exposure, flash, polarizers, tripod use, and more.
If you have any questions or would like more details, please feel free to email or call.
I needed to document the bolt holes on a wheel that came off the front of a pickup to show whether or not the wheel had been loose on its studs.
After making overall photos of the wheel and tire assembly, I made close-ups of the mounting surface and bolt holes from the back of the wheel. But on the outside of the wheel, the bolt holes were too deeply recessed to use a standard macro lens.
It was important to photograph the lug nut mating surface at the bottom of each recess, but it was nearly impossible both to get light down each recess and to fill the image frame with each hole. I wanted to get sharp, detailed, full frame images of the mating surface—not images cropped from a larger view.
The solution was the unique Laowa Probe lens. (I have previously discussed another unique Laowa super macro lens. I’ve found Laowa lenses to be well made and optically excellent.)
As the photo below shows, the Probe is a 16-inch long tube with a small diameter 24 mm lens surrounded by tiny LED lights at its end. You use a small USB power brick to power those LED lights. Laowa supplies a USB cable with a built-in dimmer switch, but you must supply the power brick. [Click on photo to enlarge, then click on back arrow to return to this post.]
Laowa offers the Probe with several different mounts for many popular DSLR and mirrorless cameras. I used the Nikon F-mount version of the Probe lens on my Nikon D850. Note that all versions of the Probe require manual focusing and exposure; there are no electronic connections between the Probe and any camera.
Fortunately, the lens barrel fit perfectly into the recessed bolt hole, allowing me to get a full frame image of the mounting surface at the bottom. All I had to do was to adjust the intensity of the LEDs, adjust the exposure, and click the shutter. [Click on photo to enlarge, then click on back arrow to return to this post.]
To steady the lens, manually focus, and keep the lens perpendicular to the bottom of the recess, I had the camera mounted on my rolling studio camera stand, which acted like an easily-adjusted tripod on wheels.
As you’ll see, the next two images made with the Probe lens required 0.5 and 0.3 second exposure times, respectively. That range of shutter speeds required that the camera be secured on a tripod to eliminate camera shake. Raising ISO to get handholdable shutter speeds would introduce noise, reduce detail, and reduce dynamic range. That would defeat the whole purpose of using the Probe to get sharp, detailed full frame images.
The first image I made for each paired hole (the wheel was drilled for two bolt patterns) was to show the bolt hole pair, while concentrating on the appropriate bolt hole. [Click on photo to enlarge, then click on back arrow to return to this post.]
I then slid the end of the Probe deeper into the recess to fill the frame with details of the mounting surface. [Click on photo to enlarge, then click on back arrow to return to this post.]
I know of no other way to have attained this image without significant cropping and the inherent loss of detail and resolution.
Although it’s not a lens I use all that often, I’ve found the Probe unmatched for photographing inaccessible labels, fasteners, or other components, too. The built-in LED lights around the lens make it a really useful tool.
-1- The Laowa Probe (along with the more recent Peri-Probe) lens is a unique, specialized macro lens that can allow you to photograph areas that are otherwise inaccessible.
-2- The Laowa Probe lens allows you to capture all the resolution and detail of full frame images that would be lost with a significant crop.
-3- If you are stymied about how to photograph a challenging subject, you might be able to find a commercially available specialized solution.
-4- While it is preferable to have specialized lenses at your disposal, you can always rent lenses (or other photography gear) for infrequently encountered situations. Of course, you might find yourself using even seemingly specialized lenses more often if you own them and have them readily available.
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.]
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.]
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.
-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.)
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.)
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.)
Now close-ups of every hole will be easily identified whether on the inside…
…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.
-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.
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.
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.]
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.]
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.]
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.
-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.
In an earlier post, I showed how shooting a sponge with a side flash gave depth to its surface that couldn’t be shown using a direct flash. I used a sponge since sponges are small, readily available, and easy to practice with anywhere. In this post, I’ll show how a side flash gives depth to an automotive subject—namely, a tire tread.
For this first image, I didn’t use any flash, but adjusted the camera for a proper exposure for the ambient light. It’s properly exposed, but the depth and extent of the cuts and chips out of the tread aren’t apparent. (Click on photo to enlarge, then click on back arrow to return to this post.)
This photo was made in my Studio Lab, which has so many LED shop lights overhead people say it looks like an operating room. Even though the room looks bright to our eyes, there is not as much ambient light for photography as you might think. In fact, to make the image above required a 4.0 second shutter speed, which obviously precluded handholding the camera. (I also increased the ISO 2/3 stop from 64 to 100.)
For the second shot, I added a Profoto B1x flash to each side, almost perpendicular to the camera, shooting across the tread. I triggered them with a Nikon SB-910 flash in the hotshoe that was pointed straight up at a very low power so it would not contribute to the exposure. (Click on photo to enlarge, then click on back arrow to return to this post.)
Side flash enhances texture by creating shadows. Diffused ambient light and direct flash lighting both evenly light your subject, which fills in the shadows, which, in turn, reduces the appearance of any textures.
[Technical aside #1: With cross-light from the added side flashes, the shutter speed was 9 2/3 stops faster at 1/200 second and the ISO was 2/3 stop less at 64, for a total of 10 1/3 stops less light than the first shot. If the flashes were turned off for the second photo, that exposure would have resulted in a pure black image. The flashes were adjusted to give the proper amount of light for the exposure. This is called a full flash image, where all of the light is provided by flash. This differs from a fill flash image where the light from any flash enhances the ambient exposure, but flash isn’t the only light source. More on this later.]
[Technical aside #2: For an equivalent ambient light image, instead of a 4.0 second shutter speed and ISO 100, you could use 1/60 second shutter speed and ISO 256,000. The 1/60 second shutter speed may allow you to handhold the camera, but ISO 256,000 is guaranteed to be extremely noisy and noticeably lacking in dynamic range. Not a good alternative at all.]
Four major takeaways:
-1- As with the earlier sponge example, flash light coming from the side brings out texture by creating shadows.
-2- Both diffused ambient light and direct flash lighting flood every surface with the same light, obscuring texture and depth differences.
-3- Indoor ambient light may look bright to our eyes, but it will require very long exposures or an extremely high (and noisy) ISO to make the photograph.
-4- You must adjust your exposure accordingly when going between ambient light and full flash lighted images.
For almost an hour, we talked about a wide range of topics related to tire, vehicle, and accident reconstruction photography. Among the subjects we discussed were the importance and use of a tripod, a polarizer, and flash. We also touched on both kinds of night photography and on post-processing.
I hope you will find the information we discussed useful. The interview also gives an idea of a couple of the topics which we demonstrate and discuss in depth in my SAE class which, by the way, will be resuming as in-person classes this year.
Here’s a link to that class: SAE C1729. I’ll post the dates of the new classes as soon as we finalize them.
Often, you’ll find you need to photograph underneath a small flap, tear, or partially broken piece. It’s quite difficult to hold the piece steady, align the lights, keep the piece perpendicular to the camera, frame the image, focus, and hold the camera steady simultaneously. Unless you have unusually long arms, many times it will be impossible to even look through the viewfinder or at the rear LCD while holding both the camera and piece, much less holding them both still and properly aligned.
You’ll want to frame your subject without cutting off important parts of it, showing lots of excess space to any side, or ending up with strange subject angles. Particularly with close-up and macro images, you’ll also want to maximize the depth of field by keeping your camera sensor perpendicular to the piece.
The only reliable and repeatable way to ensure you can get the camera where you need it—while keeping everything aligned and stationary—is to hold the piece with a clamp and support your camera with a tripod, studio stand, or even a beanbag. When both the camera and the subject are held still, you can frame the subject through the viewfinder or with the LCD, adjust the lights, and take test shots until you get your lighting just where you need it. (Click on the image to enlarge it, then click the back arrow to return to this post.)
For the torn sidewall rubber of the tire above, I used a Wimberley The Plamp II with its base clamped on the tire bead and its smaller subject clamp on the rubber flap. This securely held the flap in place so I could compose the shot and ensure the camera sensor was perpendicular to the underside surface of the flap. In my Studio Lab, I use a Foba camera stand to both place and support the camera precisely where I need it. In the field, I would use a tripod.
I held the off-camera flash in my left had so I could aim it where I wanted it, and tripped the camera’s shutter with a remote shutter cord in my right hand. (A self-timer could work, too.)
This resulting image below was an overall view of the flap and tire carcass ply surfaces that had pulled apart. It was made with a ZEISS Milvus 50 mm macro lens. (Click on the image to enlarge it, then click the back arrow to return to this post.)
For overall lighting, I used two Nikon SB-R200 macro flashes on the R1C1 ring around the lens with one below and one to the right of the lens. To show the texture on the sidewall rubber and the polyester carcass cords, I used a Nikon SB-910 flash off camera to the left. (All the remote flashes were controlled via infrared from a Nikon SB-910 flash on camera in master mode.)
In the closer image below, I repeated the process using a ZEISS Milvus 100 mm macro lens to fill the frame with the torn surface textures. For a good composition, I had to reposition the camera, which was straightforward with the Foba camera stand. (Click on the image to enlarge it, then click the back arrow to return to this post.)
-1- Flaps and pieces should be held steady with some sort of clamp. It’s almost impossible to hold them in place by hand.
-2- Securely support the camera in position for the best composition and maximum depth of field using a tripod, studio stand, or even a beanbag.
-3- Align camera so its sensor is perpendicular to your subject to maximize depth of field.
-4- Use sidelighting in addition to overall lighting to show texture (or lack of texture).