Shade Communication - Part 1: Cameras

Shade Communication - Part 1: Cameras

Welcome to the first of our two part blog series about Doctor/Lab Communication and Photography. This first post features dental photographer, Dave Hutt.  Dave will get us going on learning about camera hardware, the science behind it and how to use it. The second post will be authored by our Head Ceramist, Gary Nunokawa. If you’ve ever wondered which photos, angles and exposures are really important to an accomplished dental ceramist, this will be a good read. 

Dene Lebeau

The goal in using photography, now generally understood to mean digital photography in “shade-matching,” is to provide the dental lab with additional visual information for them to use in the making of high-quality prosthetics. On the surface, this sounds simple enough, but in practice it is the source of some confusion and frustration. This is due to two main causes. One is using the incorrect photography equipment, and the other is using the photography equipment incorrectly. Solving for these will allow dentists, even those who are not familiar with digital cameras and techniques, to achieve a much higher level of accuracy and consistency. Every day and every time.

1. Use a digital SLR camera. The most common misperception is that an inexpensive “point-and-shoot” camera will be easier to use, and therefore less prone to error. Nope. As we’ll talk about in a moment, when properly set, the SLR is much easier to use in a fully automatic, and yet fully controllable way. More importantly, it achieves a much higher level of color quality (larger and more sophisticated sensors), a greater image sharpness used with a quality macro lens, and a superb “depth-of-field.”
2. Use a “twin-light” (or “point-source”) flash instead of a traditional “ring flash.” A “ring flash,” where the light source is directly on the lens axis, produces an obvious reflection on the central anteriors, which not only wipes out a lot of color information, but also minimizes the capture of surface texture and subtle opalescence. Twin light flashes, with the light sources removed off-axis a few inches, greatly reduce these problems and can still be used for the full course of intraoral photography. The Cannon MT-24 twin light and the Nikon R1 speed light are excellent examples.
3. Use a true macro lens. The higher the quality the better. Stay away from using “close-focus” zoom lenses, and although there are some excellent after-market lenses, staying with the Cannon or Nikon macro lenses (100MM and 105MM respectively) is a safe bet and good investment.

Camera Settings

1. Set the camera on manual. Doing this will allow you to do two important things. First, set the camera to a fast shutter-speed, (1/200TH of a second is ideal) which will let you comfortably hand-hold the camera with minimal vibration. Second, set the aperture to f/32 (most macro lenses are capable of this setting, although some may only go the f/22). This is where you’ll get consistent maximum “depth-of-field”.
2. Set to iso 100. The lowest iso setting on your camera will give you the best color. Higher iso ratings will increase the exposure sensitivity of course, but do so at the expense of color quality and “noise.”
3. Set the white balance at automatic (“awb” on most cameras). Most other color pre-sets usually add color to compensate for the variations from “daylight” balance in the shooting environment, but flashes and cameras can vary, so your lab will generally have an easier time color-correcting from a more neutral value of the awb setting. Trying to set a “custom-balance” can be tricky and creates errors. Doing it incorrectly causes more problems than not doing it at all.
4. Set the flash on its ttl setting. Make the flash do all the work. It will automatically and accurately adjust its output as you move closer or further away to frame your shot. Making micro-adjustments in the flash’s output is easily done on the flash control unit; slight exposure adjustments can just as easily be made on most cameras too, without changing the overall settings.
5. Auto-focus or manual-focus: it is up to you. I personally find it easier to set the lens to manually focus when I’m making intraoral photos, but others find it just as easy to use auto-focus. Experiment with it but keep in mind that one way or the other; it has no effect on the other camera settings.
6. Communicate closely with your lab! They may want you to place a gray-black-white tab in the shot along with the dental shade tab. They may prefer working with raw files. They will certainly have a preferred way to receive your files, whether by email or directly sending your memory card. Bottom line is, the best shade-matching technique is a close working relationship with your dental lab.

These thumb-nail guidelines should get you started in the right direction. We provide digital photography training to dentists all across the country, and we get more requests for help with shade-matching than anything else. Our goal, and it should be yours too, is to make this process simple and repeatable. Your lab will thank you.

Dave Hutt
Founding Partner, Training and Workshop Coordinator
dhutt@dmddigitalphoto.com