What is a Four Thirds Camera?

Mirrorless cameras using a Four Thirds sensor are a type of digital camera that utilizes a specific sensor size known as the Four Thirds format. This format was jointly developed by Olympus and Kodak and was introduced in 2003. It is commonly used in mirrorless interchangeable lens cameras (MILCs) and is characterized by its compact size and lightweight design.

One of the key features of mirrorless cameras with Four Thirds sensors is the absence of a traditional mirror mechanism found in DSLRs (Digital Single-Lens Reflex). Instead of using a mirror to reflect light onto an optical viewfinder, mirrorless cameras rely on electronic viewfinders (EVFs) or the camera’s rear LCD screen for composing and reviewing images. This mirrorless design contributes to the smaller form factor and lighter weight of these cameras. The Four Thirds sensor size measures approximately 17.3 x 13.0 millimeters, which is smaller than the APS-C sensors commonly found in many DSLRs and mirrorless cameras.

However, the smaller sensor size offers some advantages. It allows for more compact lens designs and a reduced lens-to-sensor distance, enabling smaller and lighter lenses. Additionally, the smaller sensor size generally results in a deeper depth of field, which can be advantageous for certain types of photography such as landscape and street photography. Four Thirds cameras also benefit from a wide range of lenses specifically designed for this system.

Olympus and Panasonic are the primary manufacturers of Four Thirds lenses, although other third-party lens manufacturers also produce lenses compatible with the format. These lenses often feature advanced optical technologies, image stabilization systems, and weather sealing for enhanced performance and durability. Mirrorless cameras with Four Thirds sensors have gained popularity among both enthusiasts and professionals due to their portability, advanced features, and high image quality.

They offer a wide range of functionalities such as fast autofocus systems, high-speed continuous shooting, 4K video recording, and in-body image stabilization (IBIS)^[1]. The IBIS system is particularly notable in Four Thirds cameras, as it provides stabilization for any lens attached to the camera body, even those without built-in stabilization.

It’s worth mentioning that while the Four Thirds system was initially popular, the Micro Four Thirds (MFT) system has become more prevalent in recent years. In 2008, Panasonic and Olympus introduced the Micro Four Thirds system, which is a variant of the original Four Thirds system. The Micro Four Thirds system utilizes a smaller lens mount and a shorter flange focal distance compared to the standard Four Thirds system, resulting in even more compact camera bodies and lenses.

The Micro Four Thirds system retains the same sensor size as the Four Thirds system, measuring approximately 17.3 x 13.0 millimeters. However, the removal of the mirror and optical viewfinder allowed for a reduction in the distance between the lens mount and the image sensor, resulting in a more compact system overall.

Panasonic and Olympus were the key manufacturers driving the development of the Micro Four Thirds system, with both companies releasing mirrorless cameras and lenses based on the format. The system gained popularity due to its smaller size, lighter weight, and versatility for various photography genres, including travel, street, and videography. The Micro Four Thirds system also benefited from an increasing number of third-party lens manufacturers producing lenses for the format, further expanding the lens selection available to photographers.

Since its introduction, the Micro Four Thirds system has seen continuous advancements and improvements, including enhanced autofocus systems, improved image stabilization technology, and video capabilities such as 4K recording. It has attracted a dedicated user base of enthusiasts and professionals who appreciate the system’s compactness and image quality.