The Optical Viewfinder
Optical viewfinders, as used in all ARRI cameras, provide by far the most comfortable, accurate and efficient way to work when capturing images.
Optical Viewfinder Advantages
Operators see a full color image through the taking lens, and are able to accurately judge focus, which can save hours of aggravation and re-takes. Many cinematographers have also gotten into the habit of lighting through the viewfinder, i.e. of judging the image as they see it in the viewfinder.
With electronic viewfinders, the image from the imaging sensor always needs processing before it can be displayed in the viewfinder, resulting in a delay that can be up to multiple frames. This is especially confusing when shooting music videos or remotely operating on a crane. Optical viewfinders show exactly what is happening, right when it is happening.
Optical viewfinders show an area larger than the image recorded on film, ensuring that microphones, light stands and other debris do not make an appearance, thus minimizing the need for re-takes and saving precious time on the set. Operators find this extra area around the image also crucial for precise composition and exacting camera movements. This extra area is of course also visible in the video assist image.
In addition, optical viewfinders work without power, are less fatiguing to the eye than electronic viewfinders and can be equipped with a range of accessories like medium and long eyepiece extensions, eyepiece levelers and heated eyecups. Viewing is possible through spherical and anamorphic lenses
Modular concept of viewfinder accessories.
How Does an Optical Viewfinder Work?
An optical viewfinder is essentially a small rear projection screen and a magnifying glass. Light from the taking lens forms an image on a screen. For 16 mm cameras, this is usually a fiber optic screen, and for 35 mm cameras it is usually a ground glass.
The rest of the viewfinder is a very sophisticated magnification apparatus that allows the operator to view this image properly. Since the image on the screen will be magnified about 8 times by the viewing system before it reaches the human eye, high quality viewfinder optics and precision assembly are crucial.