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مرشحات الألوان - ٢ - مصدر الضوء .. كيفية التقاط وتطوير الصور الملونة
FILTERS FOR COLOUR
NEUTRAL DENSITY FILTERS
These are plain grey filters , in different strengths , and simply reduce the over- all exposure to the film . As it is usually possible to do just this by closing down the aperture or shortening the shutter speed , they are not often needed , but can be useful if you have a very fast film on a bright day , or want to limit the depth of field to a narrow zone . Alternatively , you might want to introduce motion blur with a long shutter speed .
GRADUATED FILTERS
These very useful filters are toned over a part of the area , with the remainder clear . The division between the dark and clear halves is shaded gradually , so that in use there is no obvious line between the two .
DIFFUSING FILTERS
The glass in these filters is usually either mottled or etched in some way to break up the definition of the image slightly . The exact effect varies between makes , but in general they conceal detail ( which may be useful in a portrait , to hide skin blemishes ) , and create a halo around subjects in backlit shots .
FOG FILTERS
Superficially similar to diffusing filters , these cut both colour saturation and contrast , in much the same way as real fog and mist . Some fog filters are graduated as well , so that just the upper half of the filter is affected ; this can , with the right view , give a more natural treatment , with the fog appearing to increase with distance .
TOP A graduated filter was used here to tone down the sky so that the buildings were not drowned by excessive contrast .
ABOVE The mottled glass of a diffusing filter is particularly effective in portraiture .
LEFT The atmospheric effect of the mist was enhanced with the aid of a graduated fog filter .
Fog Filters
With filter A
With filter B
Fog filters can be of different strengths , the top picture , using filter A , is less affected than the one below , using filter B. They can be combined to produce an effect similar to dense fog . The effect can be varied by changing the aperture of the lens , but stepping down too far will tend to cancel out the filter .
Neutral Density Filters
With NO x 2
With ND × 4
With ND × 8
Neutral density filters are used to limit the amount of light entering the camera lens for three reasons : to adjust for the film speed of for example , you are using a very fast film on a bright day ) ; to lower the shutter speed for special effects ; and to decrease the depth of field .
Diffusing Filters
Standard
With Duto
Standard diffusing filters give an overall soft- focus effect because of their uneven surfaces . With the ' Duto diffusing filter from Hoya , which has fine concentric lines etched onto it , the centre of the image remains sharp .
FILTERS FOR COLOUR
NEUTRAL DENSITY FILTERS
These are plain grey filters , in different strengths , and simply reduce the over- all exposure to the film . As it is usually possible to do just this by closing down the aperture or shortening the shutter speed , they are not often needed , but can be useful if you have a very fast film on a bright day , or want to limit the depth of field to a narrow zone . Alternatively , you might want to introduce motion blur with a long shutter speed .
GRADUATED FILTERS
These very useful filters are toned over a part of the area , with the remainder clear . The division between the dark and clear halves is shaded gradually , so that in use there is no obvious line between the two .
DIFFUSING FILTERS
The glass in these filters is usually either mottled or etched in some way to break up the definition of the image slightly . The exact effect varies between makes , but in general they conceal detail ( which may be useful in a portrait , to hide skin blemishes ) , and create a halo around subjects in backlit shots .
FOG FILTERS
Superficially similar to diffusing filters , these cut both colour saturation and contrast , in much the same way as real fog and mist . Some fog filters are graduated as well , so that just the upper half of the filter is affected ; this can , with the right view , give a more natural treatment , with the fog appearing to increase with distance .
TOP A graduated filter was used here to tone down the sky so that the buildings were not drowned by excessive contrast .
ABOVE The mottled glass of a diffusing filter is particularly effective in portraiture .
LEFT The atmospheric effect of the mist was enhanced with the aid of a graduated fog filter .
Fog Filters
With filter A
With filter B
Fog filters can be of different strengths , the top picture , using filter A , is less affected than the one below , using filter B. They can be combined to produce an effect similar to dense fog . The effect can be varied by changing the aperture of the lens , but stepping down too far will tend to cancel out the filter .
Neutral Density Filters
With NO x 2
With ND × 4
With ND × 8
Neutral density filters are used to limit the amount of light entering the camera lens for three reasons : to adjust for the film speed of for example , you are using a very fast film on a bright day ) ; to lower the shutter speed for special effects ; and to decrease the depth of field .
Diffusing Filters
Standard
With Duto
Standard diffusing filters give an overall soft- focus effect because of their uneven surfaces . With the ' Duto diffusing filter from Hoya , which has fine concentric lines etched onto it , the centre of the image remains sharp .
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