In my last column I talked about different flash systems. The purpose of the flash is to throw light on whatever it is you are photographing. Well now that light has bounced off the subject and has to be channeled to the sensor to capture the image. That is the job of the lens, channel the light. It can do other things to and that is what this column is about.
Let’s start with a typical dental digital camera set up to be used for dentistry. The stand type of lens is a macro lens usually 100mm I focal length. For purposes of this column I will be discussing the Canon EF (stands for electronic focus) 100mm Macro USM (stands for ultrasonic motor) Lens. Depending on the brand of camera your lens may be 105 mm or something similar. But let’s use the Canon 100mm Macro Lens as a base point and then compare other lenses to it. When a lens is referred to as a macro type, it means it is designed to take close up views of small objects such as flowers, insects, and teeth. For dentistry, this ability to focus closely on small objects is essential. The 100mm length then allows us to be 8-20 inches from the patient and still take a close up view, such as a single incisor. A macro lens can still take a portrait image that looks just like any other lens was used. The difference is that because the macro lens is designed to focus up close, you will have to stand 6-8 feet from your patient just to get the entire face into view. The Canon 100mm macro lens is also in the class of lenses rated as USM. The lens is driven by electronic controlled magnets that are very smooth and very fast. This means that when the lens, not the camera body, is set to auto-focus instead of manual-focus it will focus on the subject very fast and smoothly. Another advantage of this type of lens is its ability to be manually focused while in auto-focus mode. This is a huge advantage because you can manually focus the lens but if the patient moves or it’s the end of the day and your eyes are tired and you are a little off, the lens will make the slight correction for you. This is why I recommend setting the lens to auto-focus even if you manually focus the lens. This is assuming your lens has this capability. Otherwise you may strip the gears. But like all things these advantages come with a price. The first is weight. The first thing team members tell me at my hands on course when they pick up an SLR camera is how heavy it is. Most of the weight comes from the lens. The second disadvantage is price. The Cannon 100mm Macro Lens is close to $570. There are certainly cheaper macro lenses available that will give you the same quality of image. Sigma makes a nice 105mm macro lens that is about $380. While I do like this lens it is not smooth enough for me and takes too long to focus. But it is not UL so it is not designed to focus fast. It is simply a less expensive lens with fewer features. This is how non-dental camera stores can sell cheaper packages that sound as though they are just as good. Remember that you get less when you pay less. Another less expensive macro lens is the Canon EF 60mm Macro USM lens that comes with the Canon Rebel 350, a watered down version of the canon 20D. Both camera and lens are very nice for those on a tighter budget. But there is something to keep in mind. The 60mm focal length means you will have to get very close to the patient to take the images. I mean very close. This may make some patients uncomfortable unless you warn them first. And also ask the patient to close their eyes because the flash is just about an inch from their face for some views.
Now for portrait type photography there are more lenses to chose from than I could describe in 100 columns. I have already lost track of how many lenses I have and used. So let me just share two of them with you just to give you an idea of what’s available for you to choose from. For a simple, inexpensive portrait lens I like my Canon EF 28-80mm USM lens. It is very light, great quality glass, and focus quite fast. For all day shooting or just simple team and patient portraits this is a great lens. Now my absolute favorite portrait camera that in my opinion is the master of all lenses is my Canon EF 24-70 Macro USM lens. I use this lens for all of my professional shoots such as swimwear, model portfolios, etc. Because it is a macro I can get very close to the product the model is wearing yet still pull away for full body shots. This is one lens that does it all. But it comes with a big price. First, it is heavy. I don’t mean it is slightly heavier than other lenses. I mean it is heavy. But if I have to choose between one lens or having to bring a camera bag and change lenses for each shot then I don’t mind the weight. It also cost quite a bit compared to other “dental” lenses at $1140. But if you want a do all lens for portrait, not clinical, this is the best I have found.