The polarizing lens effectively absorbs these light waves, rendering outdoor scenes crisper with deeper color tones in subject matter such as blue skies, bodies of water and foliage. Perpendicularly incident light waves tend to reduce clarity and saturation of certain colors, which increases haziness. Use of a polarizing filter, in the correct direction, will filter out the polarized component of skylight, darkening the sky the landscape below it, and clouds, will be less affected, giving a photograph with a darker and more dramatic sky, and emphasizing the clouds. Actually, the effect is visible in a band of 15° to 30° measured from the optimal direction.
Hence, a picture taken in a direction at 90 degrees from the sun can take advantage of this polarization. But when looked at from the sides, the light emitted from a specific electron is totally polarized. This explains why the sky is not dark during the day. The electrons in the air molecules cause a scattering of sunlight in all directions. Some of the light coming from the sky is polarized (bees use this phenomenon for navigation ). In this situation, applying an appropriate neutral-density filter is the equivalent of stopping down one or more additional stops, allowing the slower shutter speed and the desired motion-blur effect. On a very bright day, there might be so much light that even at minimal film speed and a minimal aperture, the ten-second shutter speed would let in too much light, and the photo would be overexposed. The photographer might determine that to obtain the desired effect, a shutter speed of ten seconds was needed. This is done to achieve effects such as a shallower depth of field or motion blur of a subject in a wider range of situations and atmospheric conditions.įor example, one might wish to photograph a waterfall at a slow shutter speed to create a deliberate motion-blur effect. Doing so allows the photographer to select combinations of aperture, exposure time and sensor sensitivity that would otherwise produce overexposed pictures. The purpose of a standard photographic neutral-density filter is to reduce the amount of light entering the lens. It can be a colorless (clear) or grey filter. In photography and optics, a neutral-density filter, or ND filter, is a filter that reduces or modifies the intensity of all wavelengths, or colors, of light equally, giving no changes in hue of color rendition. If the exposure had instead been set for the unfiltered background, it would appear properly exposed while the view through the filter would be dark.
Note that the photograph was exposed for the view through the filter, and thus the remainder of the scene is overexposed. Demonstration of the effect of a neutral-density filter.
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