Filters and Digital Photography

Numerous filters that are used in analog photography can be simulated in a controlled manner on the computer. The effect of these filters can be well estimated and if need be can be undone. Among the filters that fall into this category are mainly effect and colour filter (e.g., colour correction filter, Gaussian blur, starburst filter, grid filter, colour gradient filter). These filters are seldom used in digital photography. The following article focuses mainly on filters that are used when capturing an image (e.g., polarising filters, ND filters, grey filters, grey graduation filter…) as their effect cannot be fully recreated in image processing.


Polarising filter

The polarising filter is one of the most important effect filters in photography. Its job is to reduce or eliminate the reflection of non-metallic surfaces (e.g., water or glass). The filter is only permeable for light of a certain wavelength. The colours of these surfaces are also intensified. This filter is often used to intensify the blue colour of the sky or to turn water azure blue or turquoise. The polarising filter works best when the source of light (e.g., the sun) is at a right angle to the camera. The polarising filter is pivoted and through rotation its effect adjusts to the lighting conditions. The effect of the filter can be controlled using the viewfinder or on the display screen.


Effect

  • Reduction in reflection
  • Better contrast
  • Higher colour saturation


Image with polarising filter

Image with polarising filter

Crete - Samaria Gorge

Caution!!!
This filter only allows certain light to shine through (extension factor 3-4) and should, therefore (especially in poor lighting conditions or in combination with longer telephoto focal lengths), not remain on the lens permanently.  


Further information about photographic filters can be found here http://en.wikipedia.org/wiki/Photographic_filter

 

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