Close-up Lens or Close-up Filters are lenses those mounts in front of the lens like filters to permit macro photography with minimal setup. Previously we wrote about Tips and Tricks about Macro Photography.
Working Distance of Close-up Lens or Close-up Filters
The maximum working distance of a close-up lens (the distance to the object) corresponds to its focal length and thus the reciprocal of the focal power . The refractive power of the lens is generally used in the unit named diopter (D, m -1). For a close-up lens with +2 D gives a focal length of 0.5 m, for a lens with +4 diopter gives a maximum working distance of 0.25 m. This position is the close-up lens from the object indefinitely and can be used with the normal lens at infinity focus position projected onto the image plane.
Magnification factor of Close-up Lens or Close-up Filters
As magnification m is the ratio of image size to object size B / G:
m = B/G
When Object and its image are of same size, then the magnification m is 1.
At lower working distances, the lens must be focused on smaller distance, depending on the lens used, even greater magnifications are achieved.
An alternative derivation of the operation of a close-up lens is possible with the effective focal length. The effective focal length of the array of lens and close-up lens is a direct consequence of the lens equation :
Close-up lenses can be good for infinity, take better shots than with extension tubes or bellows. The image quality of a combination of close-up lens can be as good compared to a normal lens macro lens with open apertures; superior are macro lenses, however.