|Technical Level: Intermediate-Advanced|
Do you know what your Lens Minimum Focus Distance is?
Sometimes we find ourselves in situations where our camera won’t take an image. One of the reasons this might occur is because each lens has a minimum focal distance. If we try to focus at a distance less than the minimum focus distance for that lens, the camera will not lock focus and will not take an image. This applies even if we try to manually focus the lens.
We should become familiar with the minimum focus distance for each lens we use and keep that in mind when we are using the lens. If we can’t find our lens manual we can often download the lens data from the lens manufacturer or other online sources which include the technical specifications of the lens.
For example, a Canon 100-400mm f/4.5-5.6 L IS USM Lens has a minimum focus distance of 5.9 feet or 1.8 meters. A Nikkor AF-S DX 10-24mm f/3.5-4.5 G ED lens has a minimum focus distance of .79 feet (9.5 inches) or 2.4 meters.
An analysis of the minimum focus distance for different focal length lenses indicates that longer focal length lenses typically have longer minimum focus distances.
The lens minimum focus distance is normally measured from the camera sensor to the subject. There is often a mark on the camera body showing where the focal plane or sensor is located. Click the image below for a larger image.
Some macro lenses are designed to have very short minimum focus distances. The Canon EF 100mm f/28L Macro IS USM lens has a minimum focus distance of .99 feet (12 inches) / .3m while the Canon EF 100mm f/2 USM lens has a minimum focus distance of 3 feet or .9 meters.
There are times when a longer minimum focus distance might be a good thing. A lens that focuses too close to the subject may cast a shadow on the subject. Supplemental lighting may be required in those situations. Other problems can occur when getting very close to insects or animals which may not want you to get that close. Some macro lenses have a greater minimum focus distance which may be beneficial when taking images of skittish animals and bugs.
From a trouble shooting perspective, the lens minimum focus distance is one of the first things you might check when your camera will not capture an image and you are relatively close to the subject.
Enjoy the journey.