Certos optical accessory rangefinders were introduced by the German firm Certo in 1951.
Base of the Certos rangefinder is 51 mm, while measuring range from 0.9 m (some examples 1 m) to infinity, the last marked distance is 10 m. A pretty convenient adjusting wheel rotating around a clear distance scale is located on top of the body. It's noteworthy that Certos is extremely easy to calibrate when needed, as the distance scale can be easily rotated to needed position after loosening a single fixing screw.
The Certos is well built, with solid metal construction. The rangefinder is very accurate, sadly the optical quality is rather disappointing - the picture from the rangefinder (indirect) window is hardly visible in the viewfinder, making the device usable for very contrasty subjects only. It can be however remedied by installing a 4x to 8x grey (or any other colour) filter in the viewfinder window, what makes the second window picture relatively brighter.
Five versions of the Certos exist, differing with mounting shoes:
- Modell A (literally Certos Entfernungsmesser Modell A) - intended for Altissa and Welta cameras, with a traditional horizontal mount with high shoe on the right hand side;
- Modell B - for Beltica II, with a horizontal mount with low shoe on the right hand side;
- Modell C - for Durata II, with a horizontal mount with low shoe on the left hand side;
- Modell D - with a vertical mount;
- Modell N - without mounting shoe at all.
- Of the examples known to Camerapedia editor Grzesio.