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Category: Hobbies & Recreation : Photography
Contrast Filters (for monochrome film)
Looking at the diagram of the colour wheel, this conveniently indicates some colours as being opposite (or more correctly, 'complementary') to others. Yellow is complementary to blue, red is complementary to blue-green (cyan), green is complementary to purple-pink (magenta).
When we use a filter of a certain colour, that filter absorbs more of the complementary colour and transmits more of its own and similar colours. Thus yellow and orange filters absorb more blue light and pass more yellow-orange light. A green filter absorbs purplish and reddish colours whilst passing green and close colours.
This principle is used in monochrome photography to increase or decrease the contrast between different colours.
One such application where this is often exploited is in architectural photography. Yellow, orange and red filters are often used to dramatically darken the blue sky, thus making the building stand out with impact.
Another situation is in outdoor portraits where the person is near some green foliage. A yellow-green filter will slightly lighten the foliage, while giving the impression of the person having a healthy tan complexion. And of the course the photographer could switch the colour rendition, to lighten the skin and darken the foliage, with a magenta (purplish-pink) filter.
Some common contrast filters used in monochrome photography are:
No. 25 Red
No. O(G) Orange
No. K2 Yellow
No. X1 Green
Colour Conversion and Balancing Filters
So we can get accurately rendered colour photos with different lights, we use colour balancing filters. Colour balancing filters would normally be used:
when film is intended for daylight / flash but the lighting is artificial (tungsten),
or
vice versa, when film is intended for artificial, but lighting is daylight / flash;
when weather is overcast or wet;
at sunset or sunrise when the light has a warm colour temperature;
or in open shade when light from a blue sky is evident in the subject
Some regular colour balancing filters include:
No. 80A or 80B Medium to deep blue 
For using daylight balanced film with tungsten / halogen artificial lights
No. 82A or 82B Pale blue 
For making minor colour corrections to colour balance near sunset / sunrise, when light is 'warmer'
No. 81A or 81B Pale salmon-pink 
For making minor colour corrections to colour balance in overcast / wet weather, when light is 'cooler'
No. 85A or 85B Deeper pink-brown 
For using artificial-light balanced film with daylight / flash illumination
Similar to colour balancing filters are colour correction filters. These are used to (try to) correct for the colour variation of fluorescent and sodium vapour lamps, as well as very finely tune the colour with artifical or daylight.
Filters for Both Monochrome and Colour
These are more for reflection or brightness control, and also some for being able to focus a lens more closely than normal.
Polarising ('Pol') Filter
When faced with the problem of reflections off glass, water or other non-metallic surfaces, one way to get around this is to change the camera angle. Another way is to use a Polarising filter.
Although primarily devised for minimising (if not eliminating) nuisance reflections off some surfaces, polarisers can also be used to good effect in enhancing the colour saturation (richness) in colour pictures. Another application would be to reduce atmospheric haze.
But it should be noted that the effect of the polariser is very much governed by the angle from which the light is illuminating the subject. For the purpose of increasing the colour saturation, it works best when the light is at approximately right-angles to the camera-to-subject axis. For reducing reflections off glass / water, the best effect is achieved when the camera-to-subject axis is at an angle of approximately 30 to 40 degrees from the reflective surface.
Neutral Density ('ND') Filter
These are for situations when there is excessive light overall, such that changing the lens aperture or shutter speed is not possible, or undesirable (for whatever reason).
A neutral density filter simply reduces the amount of light going through the lens, by a certain amount (usually in increments of 2 x). It generally does not affect the colour of the light.
Close-up 'filters' (also known as supplementary lenses)
These are not filters as such in terms of affecting the quality or quantity of light passing through the lens. Instead, these specially manufactured lenses attach to a camera's prime lens which can enable one to manipulate the focussing range of the camera lens. They could be thought of as 'glasses' for your camera, in the same way that people with severe short-sightedness or long-sightedness need glasses for reading or seeing distant objects.
They provide an inexpensive entry to the world of close-up and macro photography, when the prime lens will not allow focussing any closer to the object.
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Submitted By
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David Barry |
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Photo enthusiast |
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