What Is a Rangefinder Camera and How to Use It Well
17 min read by Dmitri.Published on . Updated on .
A rangefinder is an iconic film camera design made for quick, precise focusing. Rangefinder cameras can be lighter and more compact than SLRs, but they take some getting used to and require occasional maintenance.
This guide explains what rangefinders are, how they came to be, and how they compare against viewfinders and SLRs. The article also includes focusing techniques, maintenance tips, and purchase advice.
In this guide: What is a rangefinder camera? Optical rangefinder working principle. Other types of rangefinders. Rangefinder vs Viewfinder — What’s the Difference? A brief history of the rangefinder camera. The advantages of a rangefinder camera. The shortcommings of a rangefinder camera. Rangefinder design packages and features to choose from. Things to know when buying a rangefinder camera. How to adjust your rangefinder. Focusing and composition techniques for rangefinder camera users. Support this blog & get premium features with GOLD memberships!
What is a rangefinder camera?
In photography, a rangefinder is a camera with an optical rangefinder mechanism used as a focus aid.
You can identify an optical rangefinder by a split-image inside the eyepiece that you can merge by turning a ring or a wheel.
The split image may appear as a translucent, overlapping picture or as two halves of a picture, one of which can move horizontally parallel to the other. Your split image may show up inside a small patch in the middle of the viewfinder (in a viewfinder/rangefinder combos), or it could take up the entire view. A rangefinder patch could be shaped as a rectangle, a rhombus, or a circle.
A rangefinder can be coupled to the focus or uncoupled. The former means that your camera’s lens focus changes accordingly as you adjust your rangefinder split image. The latter means that you will need to adjust the split image, then read the rangefinder value (distance) and transfer that value to your lens. More on that below.
Optical rangefinder working principle.
An optical rangefinder works using triangulation.
In Figure 1 (above, left), mirror* A reflects the image of a target object (O) into a translucent mirror (B) that merges it with the direct image line (F→F₁) into a single image F₁O₁. This indicates to the photographer that the target object O is in focus. The angle ɑ is measured and converted into a lens focus value.
Figure 1, right: O is closer than the converging point of the rangefinder images (F). Because of that, O reflects off the mirror B at a different angle than F; after bouncing off B, the reflected image appears in a different spot (O₂) than the direct image (F₁). This indicates to the photographer that the target object O is out of focus. The angle ɑ is no longer correct for the focusing distance O→B. To correct the focus, the photographer needs to change angle ɑ. Changing this angle consequently corrects the (coupled) lens’ focus value.
✱ — A is a prism/mirror combination to ensure that the reflected image is not flipped.
Other types of rangefinders.
While most film photographers will define a rangefinder as a camera with an optical rangefinder built-in, the same working principle and name apply to a whole range of devices.