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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.
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
* 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:
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?
Color Conversion FiltersAs 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.
The Color Wheeldocument.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 ColorColors 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 ApplicationsWhen 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.
Gelatin FiltersGelatin 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.
Chapter 8 Chapter 10