Photosensitive element size

Optical format

The optical format is generally expressed by the ratio of the diagonal length of the photosensitive element, that is, OF=diagonal length/1 inch=diagonal length/16mm. It should be noted that 1 inch here is not equal to the usual 25.4mm, but 16mm, that is, when the photosensitive element is 12.8mm×9.6mm, it is a 1-inch photosensitive element. This marking method is mostly used in pocket digital cameras and consumer-grade digital cameras with an aspect ratio of 4:3. The size of the photosensitive element ranges from 1/5 inch to 2/3 inch.

Size type

The aspect ratio of the photosensitive element of the digital SLR camera is mostly 3:2, and the size labeling method is different, and the size type of the photosensitive element is generally indicated. Mainly divided into full frame Full Frame (close to or equal to 135 frames, such as Canon 1Ds series, 5D Mark II 36.0mm×24.0mm, Nikon D3, D700 36.0mm×23.9mm, Nikon D3x, Sony α900 35.9mm×24mm , Canon 5D 35.8mm×23.9mm, etc.), APS-H size (Canon 1D series 28.1mm×18.7mm, lens focal length conversion factor is 1.3), APS-C size (such as 23.6mm×15.8mm, 22.2mm× 14.8mm, 20.7mm×13.8mm, etc., the lens focal length conversion coefficients are 1.5, 1.6 and 1.7 respectively). Olympus and Panasonic digital SLR cameras use photosensitive elements with a size of 17.3mm×13.0mm, an aspect ratio of 4:3, and a lens focal length conversion factor of 2.0. From the structure of the camera, there are two systems, called the 4/3 system and the micro 4/3 system.

In 1996, the APS system (Advanced Photo System), jointly developed by Nikon, Canon, Minolta, Fuji, and Kodak, came out. The APS system has been greatly improved on the basis of the original 135 film system, including comprehensive innovations in cameras, photosensitive materials, printing equipment, supporting products, etc., greatly reducing the size of the film, using a new smart cassette design, incorporating digital technology, and becoming able to record Intelligent film system for shooting data and auxiliary information. The APS system is a major change to the traditional photography system, and it should have a good development prospect. Unfortunately, it did not happen at the right time. Due to the advent and rapid development of digital cameras, the APS system was quickly eliminated.　APS system has three kinds of film frames to choose from, namely: APS-H, APS-C and APS-P. APS-H is 30.2mm×16.7mm, which is the largest frame that can be taken by APS film; APS-C is 25.5mm×16.7mm, with a part of the left and right parts blocked, and the aspect ratio is close to 3:2 of the 135 frame; APS-P It is a part of the upper and lower blocks, which is 30.2mm×9.5mm, which belongs to the ultra-wide screen format. The method of marking the size of the photosensitive element of the digital SLR camera borrows the APS standard, and the size of the photosensitive element is close to the APS-C size of 20.7mm×13.8mm (for Sigma), 22.2mm×14.8mm, 22.3mm×14.9mm (the last two sizes) For Canon), 23.0mm×15.5mm (for Fuji), 23.4mm×15.6mm (Pentax K20D), 23.5mm×15.6mm (Sony α700), 23.5mm×15.7mm (Sony α350, Pentax K200D, K10D, Km) , 23.6mm×15.8mm (for Nikon, called DX format, and Sony α300, α200), etc. are all called APS-C frame, while the 28.1mm×18.7mm used by Canon EOS-1D series is called APS-H frame.

Sensor size comparison table

43.4

27.7

13.7

5.3

3.6