Undoubtedly, focus is one of the key factors that influence the type of photo we get. Most Polaroid cameras have a fixed focus with the option to attach a macro lens, but this type of focusing doesn’t always give the best results. This is why the Sonar autofocus technology was developed.
History of the Technology
Sonar is a breakthrough autofocus technology that Polaroid developed in 1978. It was first introduced in the SX-70 cameras and closely resembled echolocation in bats. When you press the shutter button, a golden disk emits an ultrasonic pulse that bounces off the nearest object and returns to the emitter. This determines the distance to the object based on the time it takes for the sound waves to return, and the camera selects the appropriate focus based on that time.
SX-70
The first camera with Sonar autofocus technology was the SX-70. The autofocus continuously rotates the front lens element, in a range from 26 cm to infinity. If you press the shutter button halfway, you can preview the focus and depth of field, because the SX-70 is an SLR camera, which allows you to look directly through the lens. By the way, this focusing process is noisier than the models that just switch between fixed lenses. The focus is surprisingly quick, almost instant and without oscillation, which is very different from slower optical systems that sometimes need some time to find the right focus.
600 Series Cameras
600 Series Cameras
In the 600 models, Sonar technology is present in only two cameras: Impulse AF and Sun 660 . These cameras do not have a movable lens, but they do have a wheel with 5 different lenses that correspond to 5 possible focus zones ranging from 60 cm to infinity. Pressing the shutter button sends out a pulse, selects the necessary rear lens, and opens the shutter. This is a very fast and quiet process, with the camera simply rotating a small plastic wheel with tiny lenses in one precise movement.
These cameras do not have a half-press function because they are designed as quick-shoot models. They also do not indicate the focus range; everything happens when you press the shutter button.
Almost all Spectra cameras had built-in Sonar. They used the same system as the 600 series cameras, but with 10 focus zones. The autofocus feature was that when you pressed the shutter halfway, it would actually display the distance to the focus object in the viewfinder. This way, you could make sure the camera was selecting the correct object to shoot (you could also hear the ultrasonic "chirping" every time the camera sent out a pulse).
In the late 90s, Polaroid switched from sound-based autofocus to an infrared system, but Sonar was an incredibly clever and precise way of focusing, especially at a time when the optical methods used by other camera manufacturers were still quite primitive. Overall, Sonar is an extremely reliable autofocus system, with the only downside being that it can be tricked if you try to shoot through glass or mirrors, as the system is based on sound waves.
