Macro lens: 60mm or 100mm? Which one is better?
On the market,we can find macro lenses with magnification ratio (1:1) with focal lengths in the range from 40 to 200mm.
[Fot. Nikon Macro lenses].
The question is, which ones are better for dental photo-documentation? Of course, the price is one of the factors influencing our choice, but it should not be the primary criteria.
The best focal lengths for dental photography are the ones around 100mm (some models will be 90, 100 or 105mm, depending on the brand).
There are 2 main reasons why you should select a 100mm lens: minimal focusing distance and portrait photography.
With a limited budget, a 60mm lens looks attractive and it is tempting to make an extra saving to spend for a dinner with beloved ones… But please think about a lens, which will be universal.
A universal macro lens allows me to take both: intraoral and portrait photographs. Especially in portraits, you will realize the superiority of 100mm. Lenses in the range of focal length from 85 to 135mm are the best ones for portrait photography and will create less distortion, which is crucial for face analysis. Look at the illustration beneath, showing face distortion depending on the focal length.
(Fot. Face distortion.]
Lenses with shorter focal lengths will create bigger (wide angle lenses 14-35mm) or smaller distortion (50-60mm). Portrait photography is an important part of the dental documentation. A process of case analysis, esthetic treatment planning or communication with the patient is very limited without portrait photographs.
Another advantage is the minimum focus distance, which is the closest distance from the focal (sensor) plane to the object, which will stay in focus, creating a sharp image as the result. Every lens has this parameter, described in millimeters or centimeters. The shorter focal length of the macro lens, the shorter minimum focus distance… It means that you can get very close to the object.
Let’s look at the example of two lenses from Nikon: 60mm and 105mm.
For Nikon AF-S VR Micro-NIKKOR 105mm f/2.8G IF-ED lens – minimum focus distance is 30.48cm
[Fot.Nikon 105 MFD]
For Nikon AF-S Micro-NIKKOR 60mm f/2.8G ED lens – minimum focus distance is 18.49cm
[Fot.Nikon 60 MFD]
In reality, the distance from the front of the lens to the object is half of the minimum focus distance… The practical implication is, that in 1:1 reproduction ratio (maximum magnification) with a 60mm lens you are very close to the teeth. It can influence the light distribution and lead to fogging of the front of the lens, caused by the patient’s breathing.
Summary: these facts should convince you to use a 100mm lens. If your main concern is the price, consider a cheaper 100mm lens from Tokina or Tamron. Please check our Dental Photo Master Equipment section to see available models and brands of such lenses.