2011-05-01

Filter

They are almost extinct in the digital photo era, because software or the imaging processor in the camera can be used instead (at least in most cases). I'm talking about photographic filters. The image shows some out of my collection, the others I own in addition are either duplicates or just have another filter thread.
From top left to bottom right there are ...

1) polarizing filter, THE filter per se. More about that in a future post.
2) Skylight filter. I have some, mostly as a permanent lens protection. The filter is slightly reddish and removes scattered radiation (haze) from the photos.
3) yellow, 4) orange and 5) green filter, for black and white photography, see below
6) a blue incandescent light filter, allows shooting natural colors under incandescent lighting on daylight film. This need is hard to imagine in times of digital and automatic white balance.
7) Infrared filter, something quite special, also has its own post.

For demonstration what effect the colored filters would do to a black and white photo, I took a digital photo and applied such filters virtually. Using a color filter is nothing else than blocking the respective complementary color. You can easily simulate this with a photo editor. For example the yellow filter: simply set the blue color channel to zero. The image will then appear very yellow. Converting this to B&W yields the same result as if you'd taken the photo through a yellow filter.
As you can see, the color filters have an effect on the distribution of the different grey levels and can be used creatively. General, as a rule of thumb: Colors similar to the filter color will be amplified (ie brighter) and get a better differentiation, the complementary colors become darker. More information can be found here (SW Photography) and here (other useful filters) .

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