The first concept to understand here is that dentists have different requirements to conventional macro photographers.
When conventional macro photographers do close up macro shots of flowers or frogs etc, they often deliberately blur the background to enhance the subject; this is done by opening the aperture [aka pupil].
Aperture on the one hand allows more light in, but on the otherhand, wide apertures have a very narrow depth of field DOF, such that the volume in front and behind the subject is out of focus.
This is often deliberately done to enhance the subject.
A wide aperture also has the benefit of allowing more light in, so that flashes don't have to be used, and that natural lighting can be used.
However, dentists, orthodontists and prosthodontists etc often don't want the background blurred; they often want the background still in focus like this:
So if we photograph using a wide aperture to allow lots of natural light in etc, we end up with a narrow depth of field like this; note how the incisors are in focus, but the molars are blurred?
In the next example, we now use a small aperture for a wide depth of field DOF, such that both the incisors and molars are both in focus.
There is one catch!
Because a smaller aperture is used, it dramatically reduces the amount of light that can enter the camera, such that a "ring flash" like the
Canon MR-14 EX, and the latest
MR-14 EX II must be used.
You can't use the built-in pop up flash because, it is not designed to work at short focal lengths, so the subject is hyper-illuminated. Furthermore, the built-in pop up flash directs the flash above the teeth, onto the philtrum of the upper lip or nose etc. Another factor is that long Canon EF 100 mm Macro lenses etc, have long wide lenses that often obscure the beam of the flash etc. Thus, you must purchase a proper ring flash. These days, it seems that Nikon only makes the Y-type flash, which may not be quite as ideal, however this is debatable depending on preference.
Now, the next factor is that you need something like a
Canon EF 100 mm f/2.8 Macro lens.
The macro-type lens allows you to get close up within 0.31 meters.
The 100 mm focal length combined with the 1.6x crop/equivalence factor [more on this later] will allow you to zoom into the teeth without having to come too close to the patient, and without having to exceed the minimum focal distance.
The maximum aperture size of f/2.8 won't actually help a dentist, remembering that dentists want a smallish aperture for a wide depth of field DOF so that both the molars and incisors are simultaneously in focus.
Canon does make a premium L-Class magnesium alloy bodied
Canon EF 100 f/2.8L lens that is much heavier, and costs more than twice as much, and has superior dust proofing and weather sealing, and has superior optical qualities, but it is unnecessary for a dentist. This L-Class premium lens can be readily identified by the lovely red ring at the front.
Now, we get to the body of the camera.
Now, we have a biggish and heavyish EF 100 mm f/2.8 Macro lens, and a biggish heavyish MR-14 EX ring flash, so we want a moderately large and moderately heavy dSLR camera body like a
Canon EOS 70D.
This moderately large and moderately heavy camera body not only helps to balance out the weight, but it also provides a reasonable grip for such heavy equipment.
I would avoid the Canon EOS 100D, 1200D, and 700D because they all have such small grips, and they are too small and light to balance out the weight of that 100 mm Macro lens, and the big ring flash.
The Canon EOS 7D is okay. The 7D is slightly larger with a full size 100% optical viewfinder, and it is made of magnesium alloy for superior dust sealing and weather proofing, and it has a superior grip, especially for bigger hands. The downside of the 7D is that it is quite heavy, and the 7D is an aging model that is dying for an update, and indeed the update will be released soon, but Canon won't tell us when, as far as I know.
Now, all of these dSLR bodies from the 100D, 1200D, 700D, 70D and 7D have APS-C size sensors at 22.3 x 14.9 mm.
The bigger 6D, 5DIII, and 1D have full frame 36 x 24 mm sensors.
The 3/4 size APS-C size sensors are an advantage to dentists due to the 1.6x crop/equivalence factor that zooms into the teeth, rather than looking at the whole face. This 3/4 size sensor also has a deeper depth of field DOF than full frame 36 x 24 mm size sensors.
The full frame 36 x 24 mm sensor is generally fitted to larger and much more expensive camera bodies.
Mobile phone cameras are very portable, but can't do much.
Compact cameras with a similar form factor to a cigarette box are compact, but can't do much either, especially in terms of ring flash and light distribution. Ten to 15 years ago, Nikon, Olympus and Kodak did make compact cameras with dental capability, but such models are no longer made.
Midsize mirrorless interchangeable lens cameras MILC have no optical viewfinder OVF and dSLR mirror mechanism, and instead use an electronic viewfinder EVF, so they are much smaller and lighter than dSLR cameras.
Examples of MILC's include the Olympus OM-D series, the Panasonic Lumix GH3 - both with medium sized micro 4/3 sensors at 17.3 x 13 mm, and the Sony Alpha A6000 with a 3/4 size APS-C sensor, and the Sony Alpha 7 with a full frame sensor.
However, be careful of the sensor size and the crop factors, the need for 100 mm Macro equivalent, the need for a ring flash for close up light and distribution, and remember that with that 100 mm macro lens, and the ring flash, you need a reasonably large grip to hold, and a reasonably large and heavy body to balance out all that weight so that it is not too head heavy. There is no point packing a big heavy 100 mm macro lens and ring flash onto a little body with a tidly grip that you cannot grip properly, and that is too head heavy.
Thus, a dSLR with a 3/4 size APS-C sensor like the Canon EOS 70D is a good choice. The 70D also has good video capability.
The more expensive Mg alloy is great for big hands, but may be too heavy with all the accessories for some, and is an aging model with limited video capability.
Keep in mind that the dSLR isn't just used for the postgrad course, it is an investment in your entire 40 year career.
You get what you pay for...
