How close depends on how much zoom you have. If you're using a 28mm lens, the magnification will not be too significant. The magnification goes higher with increase in zoom.
Lens FL refers to the focal length of the camera lens that the close up lens is designed for. Use with a different lens FL may cause sharpness to suffer.
Diopters are the optical strength of the CU lens. Its focal length can be calculated by using FL = 1000/Diopters. This is also the distance that will now be in focus when the lens is focused at infinity. (A +2 diopter will bring a subject at 1/2 metre {500mm} away into focus.)
To estimate minimum focus distance convert the camera lens minimum distance to diopters and add it to the CU lens strength. So a +2 CU lens used with a lens that focuses to 1 metre will act (approximately) like a +3 CU lens and bring a subject at 1/3 metre into focus.
Another approach is to calculate magnification. Convert the diopter strength to millimeters focal length (CU FL = 1000/Diopters). Then divide the camera lens FL by the CU lens FL to get the magnification when the lens is focused at infinity. Thus a +2 CU is 500mm FL. If you use it on a 50mm lens you will get 1:10 life size. The same +2 on a 300mm lens will give you 0.6 of lifesize (1:1.66).
Originally posted by currahee thanx for all the info...
so closeup lens actually helps to reduce the focussing distance so that u can take closer shots rite?
