The focal length of the SLR camera lens is calculated
Take 50mm as an example. In the full camera do not multiply by the coefficient, that is, 50mm, full-size cameras such as Canon 5D2, Nikon D700.
On the APS-C frame camera, multiply the coefficients of 1.5-1.6. Such as Pentax K5 Nikon D90, Canon 550D 60D are APS-C format. Canon APS-C frame camera is multiplied by 1.6 coefficients.
In the 645 amplitude camera, divide by 1.4--1.6 and the coefficient is equivalent to 36mm lens. Such as Pentax 645D
The focal length of the lens is basically the distance between the center of the lens and the clear image formed on the film plane.
The focal length of the lens determines the size of the image taken by the subject on the film. Assuming that the same subject is being photographed at the same distance, the longer the focal length of the lens, the larger the image formed by the subject on the film.
For example, the image taken with a 100mm lens is twice the height and width of the image taken on the same camera using a 50 mm lens. The height and width of the 400 mm lens are four times the height of the 100 mm lens,
Take 50mm as an example. In the full camera do not multiply by the coefficient, that is, 50mm, full-size cameras such as Canon 5D2, Nikon D700. The focal length has a conversion factor on the non-full camera, multiplied by a factor of 1.5-1.6 on the APS-C frame camera. Such as Pentax K5 Nikon D90, Canon 550D 60D are APS-C format. Canon APS-C frame camera is multiplied by 1.6 coefficients.
Normal APS-C frame camera lens focal length X1.6 on the line.
Other frames to see the specific CCD / CMOS size, with a full part of the size of the sensor in addition to the size of the photosensitive element to be magnified, with the lens focal length X ratio on the line.
