# Close-up Filters, when? How?

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#### bernards

##### New Member
How does Close-up filters work? And when is it applied? I can't seem to find any technical information on the application of Close-up filters. Thanks!

#### megaweb

##### Moderator
Staff member
bernards said:
How does Close-up filters work? And when is it applied? I can't seem to find any technical information on the application of Close-up filters. Thanks!
work exactly like a magnifying glass ..

#### justarius

##### Senior Member
bernards said:
How does Close-up filters work? And when is it applied? I can't seem to find any technical information on the application of Close-up filters. Thanks!
Close filters are used in macro photgraphy.. when you want to make small things look big.... They come in different strengths eg 5T, 6T for different degree of magnification.

#### azone

##### New Member
Close-up filters comes in a variety of diopter ratings (e.g., +1, +2, +3, +4, +10). These ratings refer to the magnification power. Close-up filters are meant to reduce the minimum focusing distance of your existing lens. By being able to focus at a shorter distance, the object will look bigger. The higher the diopter rating, the shorter the minimum focusing distance, and hence the bigger the magnification.

#### bernards

##### New Member
Thanks for the clarification guys.

On the technical side. If I have a minimum 10 cm distance for macro. How many cm did I just reduce by using a +4 close up filter?

I just bought a set of Hoya filters that come in +1, +3 and +4. Can I stack them one infront of another to get closer?

#### willyfoo

##### Senior Member
Here's the calculation... the optimal focusing distance for the closeup lens/filter is
1000mm / x (Where x is the sum of all the numbers added together)

Eg. If you have just a +4 filter..
1000mm / 4 = 250mm = 25cm distance (Same as Canon 250D)

Or you can stack a +4 & +2
1000mm / (4+2) = 166.66 mm = 16.6cm

If you need to get to 10cm, then you need the +10
1000mm / 10 = 100mm = 10cm

#### bernards

##### New Member
Thanks all. It's all clear like a sunny day now! :thumbsup:

#### hwchoy

##### Senior Member
may I ask from where this 1000mm comes from? I understand the calculation but could not relate this 1000mm to a physical property.

Also I have the Canon 250D and the Hoya +4, given both have the same magnifying power, how come the Canon is like three times as heavy as the Hoya? Not to mention the price!!

#### hwchoy

##### Senior Member
is it right? well it is thicker and heavier. will go home and examine it. in any case for prosumer cam the lens barrel is so small it uses the centre portion only.

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