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Chapter 9


Filters





Filters are made from glass, gelatin, or a liquid that is placed in front of the lens to modify light or protect the lens.

Perhaps the most important aspect of filters is their cost. Should you need to use several filters try to purchase lenses that have the same diameter filter mount. This way you will not need to buy duplicate filters of different sizes. If you can't do that there is equipment like the Kokin system that may allow you to solve this problem relatively cheaply.

Filters for Lens Protection

Filters, such as ultraviolet and skylight, filters can be used with color or black and white film. They provide an excellent lens protection.

Filters come in different sizes. Usually measured by their diameter and in millimeters. The size refers to the diameter of the front threaded filter mount of your lens.

As an example: A 50mm UV filter is an Ultra Violet filter that is 50 millimeters in diameter. It will screw into a lens with a 50mm filter mount.

Filters can also be used over your light source to convert it into a source of illumination compatible with your film.

This can be easily, and inexpensively, done with a gelatin filter. For example: You can tape a gelatin filter over your electronic flash. This technique works very well and is a fine way to match the output of a flash to the predominate light in a room.



Filters For Color and Black and White Photography


Neutral Density Filters

Density of filter
% Light Transmitted
Filter Factor
Dummy *
100.0
1.0
0.10
80.0
1.2
0.20
65.0
1.5
0.30 [2X]
50.0
2.0
0.40
40.0
2.5
0.50
32.0
3.1
0.60 [4X]
25.0
4.0
0.70
20.0
5.0
0.80
16.0
6.2
0.90 [8X]
13.0
7.7
1.00
10.0
10.0
1.20
6.3
15.8
1.30
5.0
20.0
1.50
3.2
31.2
2.00
1.0
100.0
2.50
0.32
312.0
3.00
0.10
1000.0
3.50
0.032
3125.0
4.00
0.001
10,000.0

* Colorless filter for focusing when ND filters are being used.

Neutral density filters absorb light without changing the characteristics of the light. That is to say the color temperature is not altered. Use these filters when the amount of light reaching the film needs to be reduced, but not altered.

When combining ND filters multiply their filter factors together. For example: When combining a 0.40 plus a 0.50, the resulting filter factor is:

(2.5) x (3.1) = 7.75



The Polarizing Filter

This is really two Polaroid disks in a common holder. One disk screws into the lens and is held fast while the other is able to rotate in front of the firmly seated disk.

By looking through the camera and rotating the moveable disk you can actually watch the reflections come and go. Ditto when you use it to create that beautiful blue sky. You choose the amount of blue you want.

Filters for Color Photography

These filters, with the exception of the polarizer, are used to modify light for specific film. Color Temperature Correction Filters, or CC filters for short, and a color temperature meter will allow you to get perfect color rendition under just about any illumination.

CC Filters are beyond the scope of this book, but do keep them in mind should you ever need to precisely correct the color of a photograph.

Failure to correct the light-film combination will result in colors not being rendered properly.

For example: If you have ever used daylight color film indoors under incandescent lights you have seen a red cast to the pictures. This red cast exists because incandescent light contains more red light than the film is designed for. So, you get an over response to the red light.

Under fluorescent lights your photos will have a nice shade of green with daylight film exposed without a correction filter. Note: this is a great technique to use when you are photographing people you don't like. You get green skin tones. Let's just keep that little bit of nastiness between us, shall we?

Don't despair. If you have a photo that needs color correction. See a competent photo finisher or a professional lab. The problem may be able to be fixed in the darkroom.


Color Conversion Filters

As we mentioned in the gelatin example these filters can convert the light you are using into what is required for your film.

These filters can allow you to use daylight film indoors under incandescent or florescent lights. Here the filter will "adjust" the indoor light so it is compatible with your daylight film.

These filters can be made of optical glass or gelatin.

Color Balancing and Other Filters for Color Film

Filter Number Film Type Remarks
Sky 1A Daylight Reduce blue, adds warmth.
80B Daylight Balances daylight film for use with 3400oK lights.
85 Daylight Balances Type A, 3400oK film, for use with daylight and electronic flash.
85B Tungsten Balances daylight to Tungsten, 3200oK film.
FL B Tungsten Converts fluorescent light to better balance.
FL D Daylight Converts fluorescent light to better balance.
Polarizing All types Darkens sky, water in marine scenes, reduces reflection, flare and glare when at the proper angle.



Filters for Black and White Photography

Subject
Effect
Filter
Clouds against clear blue sky or as a background. Natural sky. Medium yellow/light green.
Darker than normal sky. Dark yellow/orange.
Very dark sky. Red
Almost black sky. Dark red
Night effect. No 25 + Polarizing filter
Fabric including draperies, upholstery, clothing, etc. To darken. Complementary color to subject. *
To lighten. Filter of same color.
Flowers Lighten green foliage to make dark flowers stand out. Light green.
To lighten flowers to make them stand out against dark leaves. Filter as close as possible to the color of flower.
Glass objects. Pottery, china, etc. To reduce unwanted reflections. Polarizing filter.
To darken for increased contrast and to show detail. Complementary colored filter. *
Landscapes. Natural.Medium yellow.
Increase contrast and reduce haze.Dark yellow or orange.
Greater contrast and haze reduction.Red.
Marine scenes and subjects. Natural rendition of water. Medium yellow or light green
Darkened water. Orange or dark yellow.
Outdoor portraits with sky showing. Natural skin tones and natural sky. Light green.
Polished surfaces, waxes floors, tiles, linoleum, Formica. Reduce reflections.Polarizer.
Portraiture. Reduce contrast between blemishes and skin tone. Medium yellow or dark yellow.
Darken skin tones to emphasize tan or rugged, masculine quality. Light green.
Sand and snow lighted by sun with blue sky. Natural.Medium yellow of light green.
Increase contrast to emphasize texture. Dark yellow, orange or red.
Wood. Emphasize grain of dark wood.Red
Emphasize yellow wood, maple, oak, walnut. Dark orange or yellow.
Emphasize grain in light wood. Medium yellow.
Clouds against blue sky or as a background. Natural sky.

Medium yellow or light green.
Darker than normal sky. Dark yellow or orange.
Very dark sky. Red
Almost black sky. Dark red.

* Complementary color is found with a color wheel. Red is opposite Cyan. Blue is opposite Yellow. Magenta is opposite Green.

The Color Wheel

document.write('Click') for a more extensive color Wheel.

The Color Wheel graphically shows the relationship between primary and secondary colors. Primary colors (red, yellow, blue) are separated by secondary colors (orange, violet, and green).

Primary Colors cannot be made by mixing the other colors. You can mix two primaries to get a Secondary Color, but you can not create primary colors. The complement of any color is its opposite on the color wheel.

Complementary colors contrast drastically with each other.


The Human Perception of Color

Colors are nothing more than different wavelengths of light. Color complements have drastically different wavelengths and can cause perception problems for the viewer if placed close together in a work of art or photograph. This is because The rods and cones contained in the retina of the human eye cannot respond to such a large amount of visual information. So, we perceive a quivering or other optical distortion when two complements are used near each other.


Other Applications

When you are picking out clothing you can use the color wheel to determine if the colors clash.

Or, when you want that splash of color to set off an outfit or a photograph. The perfect color can be easily found. What you want is contrast, so pick that accessory from the opposite color on the color wheel. Just look at the color of your clothing and pick the its opposite.

And you thought this was just a photography book!


Filter Affect On Primary Colors

Filter: Affect on the primary color
red.
Affect on the primary color green. Affect on the primary color blue.
Yellow
Transmits and lightens. Transmits and lightens. Absorbs and darkens.
Green
Absorbs and darkens. Transmits and lightens. Absorbs and darkens.
Orange
Transmits and lightens. Absorbs and darkens. Absorbs and darkens.
Red
Transmits and lightens. Absorbs and darkens. Absorbs and darkens,
Blue
Absorbs and darkens. Absorbs and darkens. Transmits and lightens.



Filters To Lighten or Darken

Color of subject: Filter that will lighten. Filter that will darken.
Blue Blue. Red, orange, yellow.
Blue green Blue or green. Red, orange, yellow.
Green Yellow, green, orange Red, blue.
Yellow Yellow, green, orange, red. Blue.
Orange Yellow, orange, red. Green, blue.
Red Red. Blue, green.
Purple Blue. Green.
Pink Red. Green.
Brown Orange, red Blue.



Gelatin Filters

Gelatin filters are literally made out of gelatin. They are perfect for lots of applications and their price is very attractive, especially if you have a one time need. Here is a real world situation I faced and solved with a gelatin color correction filter.

For Example. Let's say that you are working in a large room that is lit by tungsten bulbs with a color temperature of 3400 degrees Kelvin, oK. So you buy 3400oK film.

Ah, so what's the problem? You want a source of fill light and you don't have one, or do you? Buy an 80B gelatin filter that balances daylight to 3400oK and tape it over the flash tube of your electronic flash. Now your daylight electronic flash is a 3400oK fill light.



Go take pictures with perfect color.


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