HOW BLACK & WHITE FILTERS WORK
Posted by Benjamin Newton on
Top 3 reasons to use B&W Filters
- Improve Contrast between colors that reflect similar gray tones by separating them from other colors nearby.
- For Artistic Reasons - When real world conditions just don’t cut it you can use B&W filters to produce stunning images
- Remove contrast killing haze by blocking blue, violet, and UV light from the scene which improves detail, and increase sharpness
What B&W (Panchromatic) Film sees
It may go without saying but panchromatic film does not see or record color the way our eyes and brain do. In fact B&W film sees all visible colors of light as similar tones of gray. The only thing that separates those tones is the intensity of light being reflected off the surface of the subject; shadows and highlights. To put that in a real-world setting, just imagine a gray rainy day outside at the beach where the light is very flat; no bright highlights and no deep shadows. The sand, water, clouds and horizon will render about the same low contrast gray tone. Black and White filters are used to separate those colors to improve contrast at the time the image is recorded.
It’s All About Complimentary Colors
To effectively use B&W filters in the field you need to understand the concept of complimentary colors and how it influences the way film records those colors as tones of gray. In the simplest terms a colored filter will pass its own color and block its complimentary color. For example, you are taking a picture of a red rose with green leaves (below) against a black background and you choose to put a 25A red filter on your lens. The filter will pass the red light which will render the rose a very light gray and block the green light (complimentary color) rendering the leaves much darker. In turn, you could use a X1 Green filter to create the opposite look in which the rose will turn nearly black and the leaves will lighten.
We explain how each filter affects color below by using a color wavelength chart and then converting it to grayscale. These charts are a visual approximation and provides a really strong visual to help you understand of how these filters can help improve your images. The chart below is a baseline grayscale conversion without using any filters. You can see that it is very flat and lacks contrast based on color alone. This chart does not take into account the reflectivity of the subject or the overall exposure of the scene.
How to Choose a B&W filter
Hoya currently makes 5 filters for B&W film shooters to help them capture beautiful images
Use the information below to help chose the filter that is best for the situation. All black and white images were shot on Kodak Tri-X Pan film using a Canon F1 with a 50mm f1.4 lens. The color images were shot with a Sony A7R2 with a 50mm f1.8 lens. The film was scanned on a flat bed scanner and each image was processed for exposure only and contrast was not manipulated.
Hoya 25A - Red Filter
The 25A Red filter will make reds a very light gray. As we move further away on the color wavelength chart, density increases to near black as we get to green and beyond. Since the filter is on the far left of the chart it provides very dramatic contrast changes. A lot of landscape and architectural photographers will use this filter to create dramatic separation between blue skies, trees, clouds, and buildings. The filter nearly eliminates all Blue UV haze resulting in crisp, sharp images of distant subjects like mountains.
The filter can be difficult to see through depending on the lighting conditions. We recommend composing and focusing prior to attaching the filter. You will need to compensate for 3-stops of light loss when determining your exposure.
Hoya YA3 - Orange Filter
This filter is more versatile and more popular for everyday landscape shooting because it is effective but much less contrasty than the 25A Red. The orange filter helps separate each of the near colors but is less dramatic when shooting blue skies because the complimentary color pushes into the deep blue range which is beyond the typical blue sky. This translates to lighter and more natural looking tones for blue skies. It is also great on overcast days when trying to separate water, cloudy skies and foreground.
The filter is not as dark as the red filter and it is possible for most to focus and compose with the filter attached. You will need to compensate for 2-stops of light loss when determining your exposure.
Hoya K2 - Yellow Filter
This is the most popular filter for everyday shooting. It is effective at filtering out the blue/violet/UV light that kills contrast and provides a nice balance of contrast between all colors without being too dramatic. Great for outdoors, buildings, landscapes, and people. Because you only lose 1/2-stop of light it is easy to focus and compose. Your camera’s built-in meter can typically compensate accurately with the filter attached.
Hoya X0 - Yellow-Green Filter
This filter is a subtle way to help separate green tones from one another. This is best used in forests, gardens, and situations where yellow-green to blue-green foliage needs separation from one another. Yellow-green plants will become lighter and Blue-green plants will be darker. Without the filter those types of plants will render the same gray tone and lack contrast. You will need to compensate for 1 1/2-stops of light loss when determining your exposure.
Hoya X1 - Green Filter
Essentially the opposite effect created by Red. Blue skies will get lighter and have a similar tone to the clouds, leaves and trees will also be lighter. Reds and oranges will be darker. The filter is helpful when green is the predominate color in the scene and you want to create separation between each type of green. It also helps create separation between the ocean (blue-green = lighter) and the sky (blue-violet = darker). You will need to compensate for 2-stops of light loss when determining your exposure.
SOURCE: Hoya Filter USA
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