PhotographyTips.com - the #1 guide to better conventional and digital photography Become a Member iPhone Posing GuideGuide to Posing the Female Model BookGuide to Posing the Model CD
Search
Login

Member Login

Find us on Facebook
Follow us on Twitter
Find us on Flickr
Connect with us on LinkedIn

SPONSORS

Sell Photos Online

FEATURED SITES


Filters

An introduction to photographic filters


Photographic filters are available in a seemingly endless variety.
Photographic filters are available in a seemingly endless variety.

TWO PRINCIPAL CATEGORIES

Optical filters fall into two general categories – those that are used with color film and filters for black and white film. Some filters work both sides of the fence, and can be used with either color or black and white. Colored filters for black and white film are of use with color film only when a major overall color cast is what you are seeking. A deep red filter, for example, will give an image on color film an overall red appearance, whereas with black and white film, its effects are usually dramatic.

Filters can be used for digital photography in much the same way as they are used for film photography, with some notable exceptions. Filters that modify color are generally not needed in digital photography, since a digital camera's white balance achieves all the color modification that is usually necessary.

WHY USE FILTERS WITH BLACK & WHITE FILM?

The normal aim of a photographer using black and white film is to accurately reproduce a colored subject in a range of grey tones. A red sweater should be reproduced in a different grey tone than a green sweater, for example. Differentiation of colors that would otherwise appear as the same tone of gray is the main purpose of colored filters with black and white film. Filters are very useful in interpreting colors into their equivalent grey tones.

However, filters can do more for your black and white photography. You can intentionally darken a light sky and dramatically whiten its clouds. You can reduce the effects of atmospheric haze in aerial photography, create special effects, improve skin tones, remove glare from shiny leaves, draw the viewer’s attention to a particular aspect of a subject, increase contrast, eliminate or reduce reflections, reduce the amount of light striking all or part of the film, and so on. Filters, especially colored filters, are incredibly useful in black and white photography, and it pays to learn how and under what conditions to use them to enhance your images. You are in the right place to do that.


WHAT DO COLORED FILTERS DO?

Colored filters absorb light and transmit the light they don’t absorb. A filter is yellow because it absorbs blue light (its complementary color) and allows yellow light to pass through it.

We say an object - a banana, for instance - is yellow because it reflects yellow light. So, if we use a yellow filter when photographing a banana, the filter will allow all the yellow light to pass through it and reach the film.

But, what if we use a green filter when photographing a yellow banana? Will the green filter allow the banana’s yellow light to reach the film? The answer is no, it won’t. The yellow light is blocked. Well, if that’s so, you may ask, how can a yellow banana be photographed through a green filter? Good question. The answer lies in remembering that yellow light is a combination of green and red light. (See Light and its color.) So a green filter blocks the red portion but allows the green portion of the banana’s reflected light to reach the film.

On color film or using a digital camera, the banana would therefore register as being green because the red portion of its reflected light is absorbed and only its green light strikes the film/sensor. But, on black and white film, the banana would register in a pale gray tone (because a filter lightens its own color), and the only portion of the banana’s yellow light reaching the film is the green portion.

The banana’s gray tone may appear so pale as to look over-exposed, but not as much as would the tone of any object that is pure green, like a pea. A filter that is the same shade of green as a pea will make the pea look so pale as to be almost white and completely over-exposed. If green objects become so lightened that they look overexposed when being photographed through a green filter, how do you make them look normally-toned? Another good question. The answer is that you must change the exposure so they look darker. You let more light strike the film. In other words, you increase exposure.

Okay, you say, then how can I possibly know how much I have to increase exposure to make the banana or the pea, and everything else in the picture, appear in a natural tone so it doesn’t look over-exposed? A great question. And you probably expect a complex answer. Wrong! The answer is so simple. You adjust exposure in accordance with the filter factor.

It's even easier if you have an auto-exposure camera, since it does it for you automatically. You don’t have to do a thing, except attach the filter. The camera's exposure meter reads the amount of light coming through it and adjusts exposure automatically.

If you have a manual camera, simply refer to the spec sheet that came with the filter when you purchased it to learn its filter factor, and change exposure in accordance with it.

Square & rectangular filters are part of a system that permits using the same filter with different lens sizes.
Square & rectangular filters are part of a system that permits using the same filter with different lens sizes.

Why are all these filters screwed together? See
Why are all these filters screwed together? See "Potpourri of filter tips" to learn the advantage of doing this with same-size filters.

WHAT IS A FILTER FACTOR?

Thought you’d never ask. Filters have different densities. A very dense filter absorbs more light than a less-dense filter. Filter manufacturers take these light-absorption characteristics into account, and figure out what exposure adjustment is needed to properly expose a scene based on the filter’s density (the amount of light it absorbs). The necessary adjustment is termed a filter factor, and tells the filter-user how much to increase exposure. (We recommend you click on our Filter factor section to find out more.)

USE OF FILTERS IN COLOR PHOTOGRAPHY

A primary use of filters in color photography is in reproducing colors that match as closely as possible to the actual colors in a scene. (Note: Setting white balance in a digital camera will achieve proper color reproduction in most scenes without the need of external filtration.) Certain types of light may cause film to have a color cast that the human eye doesn't notice in the scene because our eyes adjust and compensate for different types of light, but film doesn’t. Filtration can be used to color-correct the light before it strikes the film. Color film filters are therefore particularly useful, indeed often essential, with slide film (also called positive, color reversal or transparency film), since color accuracy when the picture is being taken is far more critical with slide film than with color negative film. Color negative film requires filtration less than both color slide film and black and white film since so much of the final image’s appearance can be controlled and corrected at the printing stage.

Just as with black and white film, certain filters can also be used with color film and with digital cameras to create special effects, eliminate glare and to achieve other image enhancements and intentional manipulations.

Filters most-commonly used in digital photography and with color negative film are the polarizing, neutral density, ultraviolet (UV), skylight and special effects filters, with the polarizer topping the list in terms of a filter’s ability to alter and enhance our everyday photography. A filter that blocks visible light and permits infrared light to pass through it can also be considered a special effects filter, but it is actually an infrared filter, and can be used with a digital camera and with film.

EFFECT ON SHARPNESS

Most quality filters don't contribute to any loss of sharpness. In fact, increased contrast provided by the use of some filters will make the image appear sharper.


EVERYTHING YOU NEED TO KNOW ABOUT FILTERS

Each of the many available filters for all types of film is discussed in detail in this section. Their benefits and drawbacks are explained, and the most important filters are highlighted, with tips and techniques for their use. There is no great magic in the proper application of filters in photography. You just have to know what they do, when to use them to enhance your photographs and what effect they will have on exposure settings and tones. It’s that simple. We suggest you begin with the section entitled Filter quality.

SEND US YOUR TIPS

You may have filter tips and techniques of your own that you would like to share with our viewers, and we invite you to send them in. You will receive credit on the site for original tips. If you can, please send a photograph that illustrates the tip or, better yet, two pictures (a with-filter and a without-filter picture) to clearly show the effect.



Further information...

Filter quality

Filter factor

Filters for black and white film

Filters for color film

Neutral density filter

UV filter

Polarizing filter

Creative use of filters

Lenses that attach like filters

Masks

Potpourri of filter tips
Related topics...

Infrared digital photography

Exposure latitude

Light and its color