Camera Lens Parts: Distance Scale
On a camera lens parts, a distance scale is useful in some instances, while being completely useless in others.
What Is a Distance Scale?
Near the back of the camera lens, by the focusing ring, there are markings indicating the distance from the lens where objects will appear in focus. This is commonly done with a window, indicating distance from infinity down to a foot or less. Close distances are sometimes labeled macro.
Some lenses have the distance scale printed directly on the focusing ring, with a marker indicating distance.
Use of a Distance Scale
At long distances, the distance scale will read infinity, making it essentially useless. The first marking is usually at 1 meter or so, and it goes down from there until it hits macro at less than 1 foot. Even with the scale, however, it is recommended to look through the viewfinder or to use auto-focus to ensure a clear picture.
The main use comes with macro photography, that is at a very close distance. Auto-focus often does not work well at close range. Instead of having to turn the focusing ring over and over to focus, set it at a low distance or in the macro range. This will reduce the amount of focus fine-tuning.