Colour filters to control tonal relationships in a photograph
While tonal adjustments can be carried out in Photoshop - coloured glass or plastic filters can be placed over the lens to alter the tonal relationships of the final image. With black and white film this is a means of emphasizing certain tonal areas. Because filtration works on the basis of lightening colour similar to the filter, and darkening opposite colours a typical use with film is a yellow, orange or even red filter to give the sky more contrast. The blue sky becomes darker while the tone and texture in any clouds is enhanced. To understand this we need to look at the 12 step colour wheel.
Note in the following examples how the tone of each colour alters.
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no filtration with colour |
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normal black & white mode or film with no filtration |
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With yellow filtration |
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With green filtration |
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With blue filtration |
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With red filtration |
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