CHAPTER 1: How To Create 3D Anatomy Photos
The 3D photographs featured in this atlas were obtained using an old but enduring technique: stereoscopic photography. Apart from passive and active 3D viewing platforms like modern televisions and projectors, the only way to simulate depth in a 2D environment is by polarizing images for the viewer’s right and left eyes. This has been used in a number of print and online anatomy resources in addition to other non-medical applications. This “How I Do It” section intends to provide the fundamental knowledge and ingredient list to make 3D photos for work or play.
Key Equipment
Camera: A Canon EOS 6D Mark II digital SLR was used, though a similar digital SLR or mirrorless camera body will work. Recommended models include those with sensors that can capture 16-24 megapixel (or higher) still frames, as some cropping may be required.
Lens: The most important feature. A macro lens with a relatively long focal length (i.e. 100 mm) is a must. With a Canon body, a Canon 100 mm EF f/2.8 Macro fixed lens is ideal. A shorter focal length requires the camera to be positioned closer to the subject, which may generate unwanted shadows. Not to mention that it can be physically difficult to get the specimen that close to the camera on a tripod next to a dissection bench.
Flash: Also a must, as narrow apertures and low sensitivities (discussed later) mandate the use of a flash, regardless of room lighting. A lens-mounted ring flash is ideal. Again, to fit the Canon equipment, a Canon MR-14EX II Macro Ring Lite flash was used for these photographs.
Tripod: Any sturdy tripod will do. The camera, lens, flash, and macro rail (below) make for a pretty top-heavy situation so if the option is available, avoid the ultralight tripods designed for hiking or travel.
Macro focusing rail: A macro focusing rail is required to finely move the camera left and right to simulate the “left eye” and “right eye” photographs. To fit a Manfrotto tripod, a Manfrotto 454 Micrometric Positioning Sliding Plate was used, but there may be better versions out there. Don’t be alarmed by the fact that most are designed to move the camera in the near-far axis, turning the camera sideways is all that is required to adapt it.
Software: Adobe’s suite of programs (Photoshop for image editing, Lightroom for cataloging) works well. The Tethered Capture function is ideal to rapidly analyze captures, a commonly utilized feature in studio photography.
Storage: High-resolution images take up lots of space. The collection of fully processed images, reduced size images that comprise this Atlas “only” takes up about 15 GB of storage, but the original albums for all dissections were somewhere in the 50-75 GB range.
Computer: Conventional wisdom would suggest that a lot of computing power is required to process photos like this. While it certainly helps (and probably speeds up the process), most personal computers have what it takes. A 5 year old MacBook Air was used to process all of the photos in the Atlas.
Accessories: Mostly common sense things like extra batteries and storage cards for the camera, but it is worth mentioning a couple things that may not come to mind right away. Flash batteries are usually AA size and don’t last long, so it is very helpful to have rechargeables. A very long USB cable to connect camera and computer is helpful as well if you are using Tethered Capture.
Photography “Settings”
Amateur photographers tend to obsess over camera “settings” as a means of taking the perfect picture when starting out. As one learns, the meaning of aperture, shutter speed, and ISO become clearer and the more meaningful things like lighting and composition take precedence. But, for the purposes of applying macro photography to typically microscopic fields, the recipe is pretty simple.
Aperture: This is not a situation where you want the bokeh effect. It is ideal to have as much of your field, near and far, in focus. This is called maximizing the depth of field. Most of these images were captured with an aperture setting of f/32. To put that in perspective, most portrait photography where the subject is in focus and the background is blurred occurs around f/2.
Sensitivity: This is the ISO knob. In the days of film photography, high ISO basically meant you needed less light to expose the film. Modern cameras tout maximum ISO sensitivities in the 50,000 range. The problem is that those images tend to get noisy. Since you will be using a flash that will introduce as much light as you need, there is no need to risk a noisy photo. Most of these were acquired with an ISO speed of 100, which is about as low as it gets.
Shutter speed: Since the camera will be mounted on a tripod, this doesn’t matter that much. But know that most camera flashes will not sync with the shutter at speeds faster than 1/250. These were captured at about 1/160.
Image format: Capture in RAW. Do NOT capture in JPG only, or you will lose the ability to adjust white balance, exposure, and other parameters in post-processing.
Capturing the Content
Now that you have the tools, it’s time to start taking pictures. In the figure below, the distance “l” depends largely on your target. If you have equipment similar to what is described above, the focal length of your lens will be fixed. Therefore, the tripod and camera will have to be moved closer or farther away from your subject to maximize the target size in your field of view.
Begin by taking a midline, straight-on photo of your subject. Confirm that lighting and depth of field are what was intended. Make sure it looks good.
Now position the camera as the “left” viewing eye. This will eventually be the image polarized for red for the left eye to see. Capture. At the same time, capture a mental image of the central focal point of the photo to aid in the next step.
Next, use the macro rail to slide the camera about 15-25 mm to the right. The actual distance varies depending upon how much of a simulated 3D effect is desired, the variance in distance from the viewer’s eye to every element of the subject, and other factors that are outside the scope of this primer. Realign the camera by rotating it carefully to return the center to the focal point in the left eye photo. Capture. Now you have the right eye photo.
Image Post-Processing
Now get ready for what hip photographers call “post”. This step involves loading the left and right images, RAW processing, and adjusting viewable colors to create the anaglyph image. The basics are demonstrated in the video below:
You’re done!
Now that the stereo photo is captured, feel free to resize, crop, and label if needed. Labeling a 3D image is difficult to get right, but it is possible. A 2D reference photo (like in this Atlas) is what most use as an accompanying guide.
Questions? Feel free to reach out.
Neil S. Patel, MD