Learning Event 6: Use Ultraviolet (UV), Neutral Density (ND), and Polarizing Screens

Photographic Filters and Techniques
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e. Blue (Wratten no. 47, also called C5).

This filter has rather

limited usefulness in outdoor photography, but does have uses in copy work

and in separating colors when blue and another color look similarly gray

without a filter.

In landscape photography, this filter is useful for

increasing the intensity of atmospheric haze. Why you might want to do this

is discussed in the next lesson.

The blue filter effectively makes any

emulsion (ortho or pan) act as if it were colorblind. Greens and reds are

rendered as dark grays or blacks. Blues are lightened considerably (Table

2-2).

Learning Event 6:

USE ULTRAVIOLET (UV), NEUTRAL DENSITY (ND), AND POLARIZING SCREENS

There are some filters that aren't designed exclusively for black and

white film; they work equally well with color, too. The most important of

these are the neutral density, ultraviolet, and polarizing filters.

Neutral density filters are colorless. They reduce the light reaching

the lens without affecting its color in any way. If your camera is loaded

with fast film and you find yourself unexpectedly in bright light, you may

not be able to get a good exposure even though you've stopped the lens down

all the way and set the fastest shutter speed. Placing a neutral density

filter in front of the lens is another way of reducing the light reaching

the film to a manageable level. Also, some very effective photos depend on

using very long shutter speeds or very wide lens openings, or even both. A

neutral density filter is often very handy in these situations (Table 2-3).

Table 2-3.

Ultraviolet filters (also called haze filters) look almost like

ordinary pieces of glass.

They are nearly colorless and require no

adjustment for filter factor.

They serve only to screen out ultraviolet

light without affecting any of the visible colors at all. Their effect is

very subtle. Outdoor scenes, especially those of distant views, often have

a lot of ultraviolet light in them. You can't see it, but you can tell when

it's around because the day will be hazy.