Filter factor

Filter factor

In photography, filter factor refers to the multiplicative amount of light a filter blocks.

Converting between filter factors and stops

The table below illustrates the relationship between filter factor, the amount of light that is allowed through the filter, and the number of stops this corresponds to.

Calculating Exposure Increase by Formula

The number of f-stops required to correct the exposure with a given filter may also be calculated using the formula:

Filter Factor = 2X

where the exponent "X" is the number of f-stop increases required.

An example: A deep red filter with a Filter Factor of 8

8 = 23

The normal exposure will be increased by three stops with this filter.

Filter factors for common filters

The table below gives approximate filter factors for a variety of common photographic filters.

References

* Hoya Corporation, "Filters for imaging"
* Cokin S.A., "Cokin Creative Filter System"

ee also

*Filter (photography)
*Filter (optics)
*Wratten number
*Exposure (photography)
*F-number


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