Lenses are fitted to cameras based on need. We are talking, angle of view, magnification, and light gathering ability, to name a few.
Now the camera, under most circumstances, projects a miniature image of the outside world onto the flat surface of a digital sensor or film. Only the central portion of the projected images is servable as image acuity and brilliance falls off with distance from center. The central good area is called the circle of good definition. The camera format is formed by masking the projected image.
For the full frame camera, this is a rectangle 24mm height by 36mm length diagonal measure 43.3mm. For the APS-c (advanced photo system – classic) 16mm height by 24mm length diagonal measure 28.8mm. Note—dividing the two diagonal measures thus 43.3 ÷ 28.8 = 1.5 this is the origin of the “magnification factor / crop factor). We use this method when we wish to relate behaviors of lenses when mounted on different camera formats. However, the crop factor is mainly of value two a gray-hair who has been using one of the formats for years and then switches to a smaller or larger format.
Now lenses are fitted to cameras based on the size of the image format. If we fit a lens with a focal length approximately equal to the diagonal measure of the format. Such a lash-up delivers a horizontal and angle of view of approximately 45°, and by tradition, considered the “normal focal length for that format. Let me add, the diagonal angle of view for these formats will be approximately 53°. It is this, likely useless information that is most likely published. Similar as to how TV sets are sold by their diagonal measure.
Translated, the full frame has a focal length that delivers a “normal” angle of view, it is approximately 45mm however by custom the focal length is generally rounded up to 50mm. The “normal for the APS-C, is typically rounded up to 30mm. Note 30 x 1.5 = 45. This math tells me that a 30mm on an APS-C will approximately equate to a 45mm mounted on a full frame.
We need a variety of focal lengths to satisfy our imaging needs. A wide-angle is generally 70% of “normal” or shorter. Thus for the full frame, it will be 35mm or shorter. For this APS-C, this works out to 20mm or shorter.
Telephoto is generally considered twice longer then “normal”. For the full frame 50mm x 2 = 100mm or longer. For the APS-C 30x 2 = 60mm or longer. None of these values are engraved in stone.
Historically, the APS-C was a film format of the 1990’s. It was a failed format, a hybrid between film and digital. The film had a transparent magnet coat that could record digital data and a chemical coat that recorded via being developed. We had high hopes for this system but it came too late, the digital era had dawned. The APS-C never came to blossomed.
Now the camera, under most circumstances, projects a miniature image of the outside world onto the flat surface of a digital sensor or film. Only the central portion of the projected images is servable as image acuity and brilliance falls off with distance from center. The central good area is called the circle of good definition. The camera format is formed by masking the projected image.
For the full frame camera, this is a rectangle 24mm height by 36mm length diagonal measure 43.3mm. For the APS-c (advanced photo system – classic) 16mm height by 24mm length diagonal measure 28.8mm. Note—dividing the two diagonal measures thus 43.3 ÷ 28.8 = 1.5 this is the origin of the “magnification factor / crop factor). We use this method when we wish to relate behaviors of lenses when mounted on different camera formats. However, the crop factor is mainly of value two a gray-hair who has been using one of the formats for years and then switches to a smaller or larger format.
Now lenses are fitted to cameras based on the size of the image format. If we fit a lens with a focal length approximately equal to the diagonal measure of the format. Such a lash-up delivers a horizontal and angle of view of approximately 45°, and by tradition, considered the “normal focal length for that format. Let me add, the diagonal angle of view for these formats will be approximately 53°. It is this, likely useless information that is most likely published. Similar as to how TV sets are sold by their diagonal measure.
Translated, the full frame has a focal length that delivers a “normal” angle of view, it is approximately 45mm however by custom the focal length is generally rounded up to 50mm. The “normal for the APS-C, is typically rounded up to 30mm. Note 30 x 1.5 = 45. This math tells me that a 30mm on an APS-C will approximately equate to a 45mm mounted on a full frame.
We need a variety of focal lengths to satisfy our imaging needs. A wide-angle is generally 70% of “normal” or shorter. Thus for the full frame, it will be 35mm or shorter. For this APS-C, this works out to 20mm or shorter.
Telephoto is generally considered twice longer then “normal”. For the full frame 50mm x 2 = 100mm or longer. For the APS-C 30x 2 = 60mm or longer. None of these values are engraved in stone.
Historically, the APS-C was a film format of the 1990’s. It was a failed format, a hybrid between film and digital. The film had a transparent magnet coat that could record digital data and a chemical coat that recorded via being developed. We had high hopes for this system but it came too late, the digital era had dawned. The APS-C never came to blossomed.
