During my analysis of a failed tire, I noticed what looked like a tiny, tiny nail in one of the sidewalls. I looked inside the tire, but couldn’t see if the tip had penetrated the innerliner. I gingerly felt around the inside to detect if the tip had protruded through. It had. Now I had to document that.
Photographing the head of the nail on the outside was easy, but photographing the tiny tip on the inside was quite a challenge. It was both minuscule and inaccessible.Here is a photo of the nail made with my usual lens, the ZEISS Milvus 50 mm f/2 macro. (Click on any image to enlarge. Then click on back arrow to return to the post.)
Even with the arrow, it’s impossible to get any useful information about the nail tip from this photo.
I photographed that nail tip with several other combinations of lenses, lights, and camera supports, but couldn’t get close enough to it optically. Then I remembered my beanbag called “The Pod” (now sold as either The Red Pod or The Green Pod) to which I had added an Arca-Swiss-type quick release clamp.
To get the camera lens closer to the nail, I propped the beanbag with a mounted Nikon D850 and the Laowa 25 mm 2.5 to 5x Ultra Macro lens (which I discussed and showed in previous posts) on the opposite side bead. I removed two Nikon SB-R200 macro flashes from the R1C1 ring and placed them on either side of the nail tip. This photo shows the positions of The Pod and the flashes with the camera, lens, and on-camera SB-910 flash removed.
Below is the resulting single-shot, uncropped, full-frame image with the incredible Laowa Ultra Macro lens. A single shot was necessary because the beanbag setup was not rigid enough to allow for focus stacking of multiple images.
Compare the size of the nail tip in the the top and bottom photos, and recall both were full-frame, uncropped images. Considering there was such a significant enlargement of the subject, the detail in the bottom photo was remarkable despite the limited depth of field and the less-than-rigid support from the beanbag as opposed to a tripod. I’d say that about nailed it!
Except when making night photographs, I almost always use a polarizing filter (polarizer) when photographing accident sites. Rotating a polarizing filter removes glare and increases saturation relative to the angle of rotation. Fortunately, you determine the amount of rotation you need for the effect you want simply by looking through the polarizer (through the threaded side if you’re holding it, or through the viewfinder or rear LCD once it’s mounted on your lens) as you turn the outside ring. There are no settings or calculations or other analysis you have to do to get the effect you want. But, like polarized sunglasses, polarizing filters decrease the light, so you will have to adjust your exposure accordingly. Most polarizers require an additional one-to-two stops of exposure to compensate.
While a polarizer will take the glare off of roads, grass, and trees at accident sites, it has its greatest effect on tire marks. In this first image, you can tell there are multiple tire marks on the road, but they lack definition. The photograph is properly exposed, but glare obscures any detail. (Click on an image to enlarge. Click on back arrow to return to post.)
For this second image, I attached a polarizer to the front of the lens, and rotated it until I got the maximum detail in the tire marks. I had to brighten the exposure to compensate for the light lost with the polarizer. This is rarely an issue when your camera is on a tripod, but if your polarizer loses two stops of light, it might be difficult to keep the shutter speed high enough to handhold the camera.
This photograph obviously shows much more detail than you could ever extract from the first image. This increase in detail from reduction of glare is what makes a polarizer one of the three most important accessories for automotive forensic photography, along with flash and a tripod.
It’s important to remember to rotate the polarizer between each shot, and to compensate for any light loss by adjusting your exposure.
From August 12 through 14, 2019, I will be teaching the third Photography for Accident Reconstruction, Product Liability, and Testing class for SAE. This time it will be at Southeast Toyota Technical Center in Jacksonville, FL. We’ll cover a lot of material in the three days, and you’ll come away making better quality, more professional photographs from that point on, regardless of the location or lighting conditions. After all, your photographs are at least as important as any other part of your work. You’re a professional, and your photographs should reflect that professionalism. After this class, they will.
This post shows another example image using the amazing Laowa 25 mm Ultra Macro lens. In an earlier post, I discussed what that lens is, and how to best use it. For this example, I made a 5X image of a small torn flap of rubber from a failed tire.
The green box in this first image highlights the tiny flap I wanted to make an extreme close-up photograph of.
To illuminate the flap, I used a Nikon SB-910 flash mounted on my Nikon D850 camera hot shoe to control off-camera lights. I zoomed the lens all the way out to 5X magnification (5:1 reproduction ratio) to get the greatest enlargement possible. I then moved the camera on a pair of Really Right Stuff focusing rails until I was able to fill the frame with that tiny flap. Here is the result:
That is the full size image; there was no cropping. The flap was covered with small dots of colors from the oils in the rubber compound. I felt these colored dots interfered with the subject, so I turned the image black & white.
You’ll notice that both the tip and the base of the flap are going out of focus. This is due to the inherent limited depth of field with such high magnification. It would have been easy to make everything appear to be in focus by taking a couple additional photographs at different focus points, then blending them together in focus stacking software such as Photoshop, Helicon Focus, or Zerene Stacker. But the purpose of this photo was to demonstrate the lens by itself.
Using this lens can’t be done on automatic, but if you align, focus, expose, and light properly, it’s an amazing performer at an amazingly low price.
Wow, that’s quite a name for a great, unique lens, and the name should make sense by the time you finish reading this.
This photograph is a single shot of a 0.5 mm pencil lead at 4X magnification (4:1 reproduction ratio) made with that lens on a Nikon D850. I made it in my studio lab without using flash. The lens aperture ring was at f/11. I set the ISO at 160 and the shutter speed at 2.5 seconds. It is a full-frame image. In other words, it has not been cropped.
By definition, a macro lens captures an image at 1:1 or 1X or life size, which all mean the same thing: the subject will be the same size on your sensor as it is in real life. Since a full frame sensor (FX in Nikon world) is a 1″ x 1.5″ rectangle, the subject, or piece of the subject you’re showing, would have to be no more than 1.5″ wide or 1″ high.
Most macro lenses have a reproduction ratio of either 1:1 (life size) or 1:2 (half life size). These may also be referred to as a 1X or 1/2X magnification, respectively.
My 60 mm and 105 mm Nikon macro lenses (“Micro-NIKKOR” in Nikon-speak) both have a 1:1 reproduction ratio. My usual lenses are ZEISS Milvus 50 mm and 100 mm macro lenses (ZEISS calls them Makro-Planar) have maximum reproduction ratios of only 1:2, or half life size. While either 1:1 or 1:2 is just fine for much of the photography I do, I often need greater magnification for certain details—especially for tire or other product analysis photos.
If you have a camera with a high resolution sensor, you could crop the image to just the area you want to show. But by cropping, you will be throwing away pixels and restricting the size of the image you can print or project as a trial exhibit. That negates the benefit of a high resolution camera. It’s much better to capture the image full frame without cropping so you keep all the resolution your camera can deliver.
Now, this is not a lens that you just pop on your camera and start taking incredible macro photos with. It’s a fully manual lens that does not communicate with your camera. It also doesn’t have a focus ring. So auto exposure and autofocusing are out.
Here are some considerations to keep in mind when using this lens:
-1- You need lots of light or very long shutter speeds for any kind of macro work. And the greater the magnification, the more light you need. This can be tricky with the small working distances involved.
-2- Raising your ISO won’t often be a great option because any additional noise will destroy the fine details you’re trying to capture.
-3- With high magnification, both your subject and your camera need to be perfectly still. That often means clamping down your subject and definitely means using a good, sturdy tripod for your camera.
-4- There is no focusing ring on the Laowa lens. You focus by moving the lens closer to or further away from your subject. Handholding is completely out of the question. Even with a good tripod, it can be quite tedious. You’ll really benefit from a macro focusing rail. It works best with Live View zoomed in to 100%. You’ll also want to illuminate your subject with a flashlight while you focus.
-5- You set the aperture on the lens, then adjust the ISO and shutter speed to match your lighting. You’ll need some experimentation and practice to get your exposure correct. This will become easier with experience.
-6- While stopping down your aperture increases depth of field (DOF), it also increases diffraction, which destroys the fine details you are trying to capture. The greater the magnification, the less DOF you have at any given aperture. If you can’t get adequate DOF at a given magnification, you should consider focus stacking a series of photographs. That involves taking multiple images with varying focus points, then blending them in Photoshop, Helicon Focus, or Zerene Stacker. More on focus stacking in a later blog post.
-7- To ensure the greatest DOF in a single image, or just a few images, it is best to photograph with your camera as perpendicular to your subject as possible. The greater the angle your camera is to your subject, the shallower the DOF will appear. To keep an offset subject all in focus would require multiple shots stacked in post-processing.
Digital single-lens reflex (DSLR) cameras have either full-frame or cropped sensors. A full-frame DSLR sensor (called FX by Nikon) yields an image size approximately 24 mm x 36 mm, just like 35mm SLR film cameras did. Crop sensor cameras are usually 1.5x (DX for Nikon) or 1.6x (APS-C for Canon), but can be 1.2x or 1.3x.
If the full-frame image size is 24 mm x 36 mm, why is it called 35mm? It’s obviously not the length of either side. The diagonal is 43.3 mm, so it’s not that either. (Click on image to enlarge, then click back arrow to return.)As the photograph shows, it turns out that 35 mm refers to the width of the film strip, including the sprocket holes.
While the “35 mm” designation has no direct relevance to the digital sensor size, it is still useful when referring to the focal length of lens. The diagonal, horizontal, and vertical angles of view of a given lens are the same with a full-frame digital sensor as they are on a 35 mm film camera. For example, the ZEISS Milvus 50 mm f/2 macro lens has a horizontal angle of view of 38 degrees on a full-frame digital sensor just as it does on a 35 mm film camera. The cropped sensor equivalent values will be the subject of another post.
Even before I started teaching Accident Reconstruction, Product Liability, and Testing Photography classes, I’ve often been asked about what photo gear works the best for those areas.
In response, I’ve created two wish lists at B&H Photo Video: one for Nikon Nikon Gear Wish List and one for Canon shooters Canon Gear Wish List. I’m a Nikon shooter, so most of my direct experience is with Nikon equipment. Here are some notes on the lists:
-1- I currently use the Nikon D850. It’s arguably the best all-around camera on the market, but I recommend the Nikon D750 for Nikon shooters for several reasons:
– Its files are more manageable in size, but are still plenty large.
– It still has the manageable body size and shape, and even has the really useful flip up and down LCD screen.
– It has a built-in flash to use to trigger the Nikon 4804 R1 macro flashes.
– The built-in flash isn’t terribly powerful, and can’t be rotated or removed, but can be used in a pinch.
– Right now, it is on a fantastic sale—especially with the 24-120 mm lens. You save $1,200 instantly.
– It’s been out for a while, and is tried and true.
There are similar advantages for Canon shooters with the 6D Mk II vs. the 5D Mk IV. If you have the budget, the Nikon D850 or Canon 5D Mk IV can’t be recommended highly enough. But they are not necessary for the work we do.
-2- The lists show both the ZEISS Milvus 50 mm and either Nikon 60 mm or Canon 100 mm macro lenses. I use the ZEISS, but also have the Nikon. I use my ZEISS Milvus 50 mm lens for most of my work photography, since it has a normal perspective. I also use the ZEISS Milvus 100 mm lens when I need to fill the frame with a macro shot, but can’t get close enough.
Advantages of the ZEISS are: Precise manual focus; amazing micro contrast; and, 50 mm is accepted “normal” lens that I use for almost everything.
Disadvantages of the ZEISS are: Manual focus only (but that is my preference); and, only enlarges to 1:2 (or half life-size).
Advantages of the Nikon: 1:1 (life-size macro); autofocus (but see note below); close enough to “normal” focal length; and, less expensive.
Disadvantages of Nikon: Not as easy to manually focus. Note: When shooting macro images, you’ll most likely have to manually focus anyway, so having a more precise manual focusing ring is a real benefit.
Speaking of ZEISS lenses, four ZEISS manual focus prime lenses make up my work kit: the classic ZEISS 25 mm f/2 Distagon; the ZEISS Milvus 35 mm f/2; the ZEISS Milvus 100 mm f/2 macro; and, the aforementioned ZEISS Milvus 50 mm f/2 macro. I use the latter for 90 percent of my work. ZEISS makes lenses for Nikon, Canon, and Sony mounts. They have unrivaled sharpness and micro-contrast, and such smooth and accurate manual focusing that you’ll forget autofocus exists! Continue reading “Suggested Gear for Accident Reconstruction, Product Liability, and Testing Photography”
Fill flash helps bring out details in vehicle photos, especially under high-contrast lighting situations. As an example, the damage to the right front of this black car does not show up well when no flash is used. With the sun behind the car, the damaged area was in shadow. (Click on image to enlarge, then on back arrow to return.)Obviously, this car couldn’t have been driven to a more favorable spot, and it was not possible to have it moved. Besides, even if the car was moved to get better light on the right front, then the light wouldn’t have been good from other angles.
Like everything else photographically, the solution is to think about the light. Where is it? (Fairly high, and coming from the other side.) Where do you need it? (Good top light, but need light in the foreground, too.) How can you get light where you need it? (Use flash to fill in the shadows.) This is called “fill flash”. The term fill flash means that flash isn’t the only light source illuminating the subject, but light from the flash just fills in the shadows as desired.
Here’s the same vehicle in the same location with the same light, but with an on-camera flash used to partially fill in the shadows.You can see the light on the background stayed the same, but light from the fill flash now shows details in the shadows.
About half the truck wheels sold today are aluminum rather than steel. As with anything, there are trade-offs when comparing steel and aluminum wheels. Aluminum wheels weigh less but cost more than steel wheels. Aluminum wheels don’t rust, of course, but they can suffer from flange wear. Alcoa recommends checking for excessive flange wear using a simple go-no go gauge (Part No. 000700).Here’s a photograph of the gauge in use. (Click on image to enlarge, then click on back arrow to return.)While the gauge is quite easy to use, it is more challenging to photograph. It can be tricky to hold the thin aluminum gauge in the proper position while also making a photograph. To make the photograph above, I used a Wimberley The Plamp II with one end clamped on the wheel center hole, and the other end clamped to the gauge.The Plamp II is fantastic since it is flexible enough to get into any position, yet stiff enough to remain in place once released. Here’s a link on B&H: Wimberley The Plamp II from B&H. The Plamp II allowed me to quickly and steadily hold the Alcoa gauge perpendicular to the rim and properly up against the flange. It was easy to focus and shoot without any motion from trying to hold the gauge by hand. It also allowed me to get the flashes into position with no shadows from my arm across the photo.
If you need to photograph something like a gauge or ruler, it is worth taking the few minutes to secure it and light it properly. You can often just tape it in place, but that wouldn’t have worked to position this flange wear gauge.
Glare on the glass globes can obscure the filaments when photographing light bulbs. This first photo shows the effects of overhead lights reflecting on the bulb. (LO refers to Left Outside taillight bulb.) (Click on image to enlarge, then click on back arrow to return.)Below is the setup that was used to create that photo.The bulb was held in place with a Wimberley The Plamp II, and the camera was locked down on a studio camera stand. The white cabinet door was used as the background. Note that the flash was not used.
All the glare from the overhead lights was eliminated by placing a translucent umbrella on a small light stand above the bulb. That umbrella was lowered and moved around until all of the glare from the overhead lights was gone. Here’s what the setup looked like with that simple change.As you can see below, the resulting photograph had no glare, and clearly showed the filaments and the posts.Translucent umbrellas have the advantages of being inexpensive (well, except for this one by Profoto), lightweight, and compact. So this setup can be used anywhere outdoors or indoors, with a tripod replacing the studio stand. When using outdoors, typically you’ll just have one source of glare from the sun. Many times, you’ll be able to just prop the umbrella on the vehicle or ground without needing a light stand or some other holder. If it’s dark or shaded, you might need supplemental lighting (flash, LED, or other light sources). These can be fired through the translucent umbrella to prevent glare from them. That will be the subject of a future post.