Converted focal length into 35 mm camera Diagonal distance of image area in the 35 mm camera 4327 mm Diagonal distance of image area on the image sensor of the DSC focal length of the lens of the DSC. Lets say you have a reflecting telescope with an aperture of 6 inches 1524mm and a focal length of 1000mm your focal ratio is 10001524 656. The focal length of a convex lens is the distance between the center of the lens and the focal point.
As simple as that.
Inches of the focal length. The focal length is positive for a concave mirror and negative for a convex mirror. - If magnification m is positive It means image formed is virtual and erect If magnification m is negative It means image formed is real and inverted Questions Example 103 - A concave lens has focal length of 15 cm. The focal length is part of another formula which allows for calculating the focal ratio of a telescope.