Marumi macro +3 filter dhg 55 mm

Marumi DHG Macro (Digital High Grade) filters are used for close-up photography. Made of extra-strong tempered glass, they are multi-coated and moisture, scratch, and dirt resistant. This also makes DHG filters easier to clean.
Using a DHG close-up filter allows you to photograph closer than your lens indicates.
You screw the filter attachment onto the front of your lens. This filter has a diopter (strength) of +3. If desired, you can screw two filters together to take even closer photos. Extending the exposure time is not necessary. The filter has a screw-on profile on the front for attaching lens/filter accessories.

Explanation: DHG macro (pre-filter)
The strength of a close-up filter is specified in diopters, in this case +3. Use the following formula to calculate how much you can reduce the minimum focal length with a particular macro or close-up filter.

This formula is:
X : ( D * X + 1)

Where X is the minimum focal length of your lens in meters, and D is the diopter number on the Macro/Close-up lens.

Here is a calculation example:
You have a lens that can focus from 55 centimeters and you are using this close-up filter with a diopter of +3. In this case, the calculation is:
0.55 : ( 3 * 0.55 + 1 ) and this is the same as
0.55 : ( 1.65 + 1 ) or
0.55 : 2.65 = 0.21 meters, so 21 centimeters