The Marumi Close Up 3 Filter is a cost effective solution to add magnification and focus to your standard lens. Macro filters work similarly to reading glasses by enabling you to capture an object/subject close up while maintaining a sharp focus on the object. This allows you to photograph small subjects at full screen. By using a close up filter, you will be able to photograph an object from a shorter distance than your lens is normally able to.
Further, it is also possible to combine macro filters to increase the magnification of the lens without extending the exposure time. For example, a macro filter with a 2 diopter used with a macro filter with a 3 diopter provides a 5 diopter set up.
The Marumi close up filters are available in the following 4 strengths, +1, +2, +3 and +4. The minimum focal distance of each of these different strengths differs depending on the camera lens. The general formula and an application thereof is as follows:
X: (D* X + 1)
Where X equals the minimal focal point of your camera lens and D equals the diopter (or strength) of your close up filter.
The diopter of your close up filter is multiplied by the minimal focal point of your camera lens. One is added to this number and the minimal focal point of your lens is divided by this final number. For example:
0.55: (3* 0.55 + 1) =
0.55: (1.65 + 1) =
0.55: 2.65 = 0.21cm
Thus, a lens with a minimal focal point of 55cm used in conjunction with a close up filter of +3 would increase the minimal focal point to 21cm.