Filter Experiment

Objective: To demonstrate the effects of each filter when using black and white film.

Activity: First research filters and the purpose of each pertaining to black and white photography. Then, experiment with filters by taking a picture of the same scene with a filter, and without a filter, and then develop each picture and compare.

Filters to be used: Red, Blue, Yellow, and Polarizer

Part One: Research

Figure 1: Five filters used in experiment

There are basically five filters for B&W photography as seen in Figure 1: red, orange, yellow, green and blue. Although these filters are used for black and white photography, and the single layer of silver halide produces a monochrome image, it still reproduces colors - but as different shades of gray. The sensitivity to different wavelengths varies, so it reacts differently to various hues. Most general-purpose films (panchromatic) incorporate dyes to adjust their sensitivity to all the visible colors. Some color hues are brighter than others; for example, the average yellow seems brighter than an average blue. Thus, it these tones are represented in a black and white photograph to create realistic images. If all of the items in your photograph were different shades of gray, then putting these filters over the lens wouldn't do anything except require an exposure adjustment. However, for example, blue sensitivity of black and white film can result in clear skies looking too pale because most B&W films are roughly the same intensity so you end up with a white sky. Thus, by using specific filters, the sky can be corrected to have more contrast.

Figure 2: Color Complement Wheel

Most B&W landscape photographs taken by professionals are taken with a filter of some kind. One of the major used for filters is to improve contrast. A color filter placed in front of the lens will pass more of its own color and block the light of other colors. Therefore the compliment of the filter color will appear darker. Figure 2 shows a color complement wheel, useful in determining each color's complement. A red filter darkens green and blue objects more than it darkens white things. However, if the opposite will occur is the complimentary color is used- a green filter makes red objects appear darker. Looking at figure 3, you can see the effects of each filter.

Filter Color	Physical effect	Practical use
Red	Absorbs nearly all blue as well as green light	Darkens blue sky and water considerably, incleases contrast in landscapes, and lightens yellow and red subjects.
Yellow	Absorbs ultraviolet and blue-violet	Darkens blue skies and shadows, and reduces bluish haze.
Blue	Absorbs red, yellow, green and ultraviolet	Lightens blue subjects, increases bluish haze.
Green	Absorbs red light	Objects that appear red become much darker
Orange	Absorbs ultraviolet and blue	Darkens blue sky

Figure 3: Description of filter

Part 2: Experiment

For this experiment, a lot of though went into how I could easily show the differences between each filter to an audience that had little to no prior knowledge of photographic filters. I decided to choose one subject and keep as many things as possible constant. I thought about taking photographs of different subjects and demonstrating the most common uses for each filter, but I thought that would make it hard to see the connections between each filter. Then I had to find a subject that incorporated everything the five filters affected. I drove around for a least an hour scooping something to photograph. I finally choose a landscape that incorporated everything I thought necessary- the barn's roof was red, the grass was green, there were clouds- but you could see the blue in the sky. I actually I waited a week for good clouds (and actually left electronics early just to take these photographs when the clouds were perfect)
Then when exposing and developing the photographs, I tried to keep the exposure times the same for each photo. I used a tripod to take the photographs and tried to capture the same image in each photograph, just with different filters. I used similar exposure times for each photograph and used the same lens. When developing the photographs I did not use any dodging or burning techniques, and kept the exposure times the same- 5 seconds at f/22. I did not use any contrast filters because this would alter the results; for example, if I used a polycontrast filter of 4, the clouds would "pop out" more and modify the data.

*Note: I actually took a few photographs of the seen in color, but have yet to finish taking the roll to have it developed. Thus, this would be a to include if experiment is used as a teaching tool.

Part 3: Results

Red filter: overall more contrast, clouds distinctively "pop out" more, grass was darkened
Yellow filter: overall more contrast, clouds appear somewhat darker
Orange filter: overall more contrast, clouds appear darker
Green filter: overall more contrast, red on roof barn darkened dramatically
Blue filter: overall more contrast; darken sky much more than I expected

With all of the filters, I could tell a big difference in contrast, especially in the clouds and sky versus not using a filter. However, there was not a great difference between the yellow and the orange filters. The outcomes of the green and red filters were the best. You could see very distinctively how they darkened there complementary color. The outcomes of all the filters were basically as I anticipated, other than the blue filter. I think possibly I either exposed the photograph longer or the exposure in the darkroom, because I have never seen a blue filter create that much contrast or darken subjects as much. Instead of lightening blue subjects, in this case the sky, it darkened the blue.

No Filter	Yellow Filter
Blue Filter	Green Filter

No Filter	Red Filter
Orange Filter	Green Filter

Part 4: Documentation

All information was derived from readings and experience with/ about filters.

Cokin Filter System, http://www.geocities.com/cokinfiltersystem/id77.htm.

Freedman, Michael (1993). The New 35mm Hankbook. Quarto Inc., Philidelphia. Pg. 61-64
Greenspun, Phillip. Filters. http://www.photo.net/equipment/filters.html.

Haynes, Don. A guide to Black and White Photography. http://www.ubmail.ubalt.edu/~dhaynes/photo/bwhite.htm.

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