Leaf shutters

Introduction

In Photography an aperture and a shutter are used to control the amount of light falling on the film or image sensor. In the passed 100 years basically two types of shutters have been used. The shutters are named after their construction or after their place in the path of light. Based on their position we know central shutters and focal-plane shutters. Based on their construction they are called leaf shutters and two-curtain shutters.

The leaf or central shutter is positioned in the centre of the lens. The aperture is opened by leaves moving outward. Except during opening and closing the frame is continuously exposed. Flash photography is possible at any shutter speed. A downside is that the shutter is part of the lens. Exchangeable lenses have to be equipped with shutters. The shutter is an expensive part. Another consideration is that in conventional leaf shutters the fastest speed is around 1/500 s. Rollei developed a faster leaf shutter for the System 6000 PQS lenses with the classic springs replaced for linear motors and the steel leaves for super-lightweight carbon. Compur leaf shutters are well built and extremely reliable. Similar high quality although less sophisticated shutters were made by Copal and Seiko.

The focal-plane shutter is positioned behind the lens, right in front of the focal-plane. Lenses are not equipped with a shutter. Lens construction may be easier and is definitely less expensive. The downside is in flash-photography. The aperture is only fully opened at slow shutter speeds and only in that case is flash-photography possible. At faster speeds the second curtain has already started closing the aperture while the first curtain is still opening. Exposure is by means of a slit travelling along the focal plane. During exposure only a small part of the frame is exposed at any time. That makes flash-photography at faster speeds impossible. Focal-plane shutters are used in Leica’s, many 35 mm SLRs and the Rolleiflex SL 66.

Compur shutters

Nearly all Rolleiflex and Rolleicord Twin Lens Reflex cameras are equipped with leaf shutters made by F. Deckel, Munich. Deckel was owned by the Zeiss Group. Later on the production was moved to the Alfred Gautier Prontor Werk at Calmbach, also owned by Zeiss. The leaf shutter was invented by Bruns and Deckel around 1900. Their first leaf shutter was the Compound shutter. Timing was done by means of an air-brake. The Compur shutter is its successor. The name is a contraction of ‘Compound’ and ‘Uhrwerk’ (clockwork).

The basic shutter is named Compur. It has nine shutter speeds. The fastest speed is 1/300 s. To achieve an even faster speed an extra spring had to be used. This is the Compur Rapid. The top shutter is the Synchro-Compur. The name emphasises the ability to synchronise flash. It has M and X settings. M is for slow burning bulbs. The shutter is released when the bulb is burning at full strength. The X contact is used with electronic flash. This flash is immediate, very intense and short. It is triggered after the shutter has fully opened. The V stands for ‘Vorlaufwerk’ (Delayed action shutter release) also known as self-timer.

The Compur shutters were made in several sizes. #00, #0, #1, #2 and #3. The Rolleiflex 4×4 cm is equipped with a size #00 shutter. The larger size #0 can be found in the Rolleiflex 2.8 and sizes #1, #2 and #3 are mainly used with Large Format lenses.

Compur #00 size

Size #00 is the smaller one. It is present in many Rolleiflex 6×6 and all Rolleiflex 4×4 TLR cameras. The shutter is used with taking lenses with apertures up to 1:3.5. The small size results in smaller and thus lighter shutter leaves. That makes it easier to achieve fast speeds.

Compur Shutters size #00