Filter factors

Filter factors are indications of the increased exposure necessary to compensate for the density of the filter. A filter factor of two indicates the exposure should be doubled (an increase of one stop). A filter factor of four indicates the exposure should be increased four-fold (two stops) and eight requires three stops increased exposure.

Establishing an appropriate exposure

When using a camera with TTL metering the light meter is reading the reduced level of transmitted light and so theoretically the exposure should require no compensation by the photographer. In practice, when using the deeper color filters and TTL metering, it is advisable to take a meter reading before the filter is attached to the lens and then apply the filter factor. This leads to more accurate exposures being obtained as the meter can be misled by the colored light if metering through the filter.

Using more than one filter

Remove UV or skylight filters when using other filters. All filters provide UV filtration. Beware of vignetting or cropping the corners of the image when using multiple filter combinations. When using two filters the combined filter factors should be multiplied not added. If a neutral density filter with a filter factor of four is used in conjunction with an orange filter, also with a filter factor of four, the resulting filter factor would be sixteen, not eight. Adding the filter factors instead of multiplying them would lead to a one stop underexposure.

Filter factor table

Filter factor 1.25

Exposure increase in stops Density*

¹⁄³ 0.1 1.5 ²⁄³ 0.2 2 1 0.3 2.5 1¹⁄³ 0.4 3 1²⁄³ 0.5 4 2 0.6 5 2¹⁄³ 0.7 6 2²⁄³ 0.8 8 3 0.9 10 3¹⁄³ 1.0 20 6²⁄³ 2.0

* Note > The ‘Density’ of a filter is most often referred to when purchasing a neutral

density filter such as an ND1 or ND2.

Rodrick Bond

Samantha Everton

application module>>

This page intentionally left blank

lighting on location

Mark Galer

essential skills

~ Change the character and mood of subject matter using lighting. ~ Develop an awareness of overall subject contrast and how this is translated by the capture medium. ~ Develop skills in controlling introduced lighting on location. ~ Research a range of fi ll and fl ash lighting techniques. ~ Produce photographic images demonstrating how lighting techniques control communication.