D
Doug Kerr
Guest
It is common to describe digital camera sensors of the general size found in the Canon EOS 10D, 300D, 350D, and 20D as the "APS-C" size (sometimes, just as "APS" size).
We also sometimes hear the sensor size of the EOS 1D and 1D Mark II described as the "APS-H" size.
I thought it would be interesting to describe the basis for that nomenclature.
"APS" refers to the Advanced Photo System, a modern scheme for "consumer" film cameras developed in the 1990s by a consortium of manufacturers including Kodak.
The system is based on the use of a film 24 mm in width, carried in a special cartridge that facilitates automatic loading in the camera and automatic manipulation of the film in processing.
Most APS cameras allow the photographer to choose at the time of shooting from three different aspect ratios for each shot (more about them later). However, in every case, the actual frame exposed by the camera is the same size: 30.72 mm x 16.7 mm (the APS frame size).
The aspect ratio selected by the photographer for the shot is coded on the film. When the film is processed, the processing equipment reads that code and crops the image frame as required to produce a print of the chosen aspect ratio.
On many APS cameras, when an aspect ratio is chosen, a viewfinder mask is put in place so the finder view matches the chosen aspect ratio. Primitive cameras have "composing frames" for the three aspect ratios shown in the finder.
The three aspect ratios are called "H", "C", and "P". For each there is an equivalent frame size (the portion of the entire frame that will be used to produce the print when that aspect ratio has been chosen). (Recall again that for every shot, the full "APS frame" is taken.) Here are the details for each aspect ratio:
H (evocative of "HDTV format") - The full APS frame (30.2 mm x 16.7 mm) is used. The aspect ratio is 1.81, considered similar to the HDTV aspect ratio of 1.78 (16:9).
C ("classic" format) - The "delivery crop" here is 23.4 mm x 16.7 mm. The aspect ratio is 1.40, considered similar to the "classic" full-frame 35-mm camera format aspect ratio of 1.5 (3:2).
P ("panoramic" format). The "delivery crop" here is 30.2 mm x 9.5 mm. The aspect ratio is 3.18.
Now, what about EOS dSLR frame sizes?
The frame size for the EOS 10D, 300D, 350D, and 20D is on the order of 22.5 mm x 15.0 mm. APS-C, often used to suggest that general size, refers to an image size of 23.4 mm x 16.7 mm. What can I say.
The frame size for the EOS 1D and 1D Mark II is on the order of 28.7 mm x 19.1 mm. APS-H, often used to suggest that general size, refers to an image size of 30.2 mm x 16.7 mm. What can I say.
I discourage the use of "APS" nomenclature to describe sensor size families.
We also sometimes hear the sensor size of the EOS 1D and 1D Mark II described as the "APS-H" size.
I thought it would be interesting to describe the basis for that nomenclature.
"APS" refers to the Advanced Photo System, a modern scheme for "consumer" film cameras developed in the 1990s by a consortium of manufacturers including Kodak.
The system is based on the use of a film 24 mm in width, carried in a special cartridge that facilitates automatic loading in the camera and automatic manipulation of the film in processing.
Most APS cameras allow the photographer to choose at the time of shooting from three different aspect ratios for each shot (more about them later). However, in every case, the actual frame exposed by the camera is the same size: 30.72 mm x 16.7 mm (the APS frame size).
The aspect ratio selected by the photographer for the shot is coded on the film. When the film is processed, the processing equipment reads that code and crops the image frame as required to produce a print of the chosen aspect ratio.
On many APS cameras, when an aspect ratio is chosen, a viewfinder mask is put in place so the finder view matches the chosen aspect ratio. Primitive cameras have "composing frames" for the three aspect ratios shown in the finder.
The three aspect ratios are called "H", "C", and "P". For each there is an equivalent frame size (the portion of the entire frame that will be used to produce the print when that aspect ratio has been chosen). (Recall again that for every shot, the full "APS frame" is taken.) Here are the details for each aspect ratio:
H (evocative of "HDTV format") - The full APS frame (30.2 mm x 16.7 mm) is used. The aspect ratio is 1.81, considered similar to the HDTV aspect ratio of 1.78 (16:9).
C ("classic" format) - The "delivery crop" here is 23.4 mm x 16.7 mm. The aspect ratio is 1.40, considered similar to the "classic" full-frame 35-mm camera format aspect ratio of 1.5 (3:2).
P ("panoramic" format). The "delivery crop" here is 30.2 mm x 9.5 mm. The aspect ratio is 3.18.
Now, what about EOS dSLR frame sizes?
The frame size for the EOS 10D, 300D, 350D, and 20D is on the order of 22.5 mm x 15.0 mm. APS-C, often used to suggest that general size, refers to an image size of 23.4 mm x 16.7 mm. What can I say.
The frame size for the EOS 1D and 1D Mark II is on the order of 28.7 mm x 19.1 mm. APS-H, often used to suggest that general size, refers to an image size of 30.2 mm x 16.7 mm. What can I say.
I discourage the use of "APS" nomenclature to describe sensor size families.