Color theory is a fascinating topic, especially for photographers. It is important to understand the rules that govern the perception that humans have of colors. Today we will just touch the surface of this vast and complex field.
We wanted to see how different color filters would affect tones in black and white photography. We used Earl Grey B&W 35 mm ISO 100 and developed following the standard process.
The differences you see are coming from the different filter colors. We took the same image to compare how each filter would effect colors. Favoring locations where we could have a good variety of different shades.
Each filter requires adjusting the reading of the light, so each time we fixed the metering for the filter we were using. There is approximately a 1 stop difference with deep orange and green filters and 2 stops with a blue filter. This is what is usually referred to as the filter compensating factor.
We used Cokin filters: yellow A163, deep orange A172, and green P004. For the blue, we used a gelatin filter, the same you can use in the studio to color strobe lights.
Each filter favors the passing of its color while blocking the others, thus registering color in different intensities depending on which is their respective complementary color. Therefore rendering lighter or darker tonal shifts. You will see that it lightens the respective color and darkens the opposite one.
This filter blocks every other light wave except red light. The more light goes through the black and white film, the lighter it will be perceived on the film. And because more is coming through, the more you will see.
A red/orange filter is common among photographers. Generally, it boosts contrast in landscape images, especially enhancing the contrast in the sky. The blue gains intensity so the clouds are sharper and more defined against the sky. Also, it will boost foliage and leaves in landscape as green is its complementary color.
If used for portraits of people, it will lighten up the face for Caucasian skin tones, smoothing away any blemishes in the skin, and it will lower the contrast for darker skin tones. This avoids quite a lot of work in post-production.
The green filter has its perfect use for foliage as it will register the different shades of green. There will be more details and separation from the red tones. It can also work in your favor if you are looking to get more contrast in your portraits, achieving the opposite effect of the red, where instead of canceling skin imperfections it will highlight them.
Yellow can be considered an all-purpose kind of filter. It moderately increases contrast, as it affects the green colors and oranges, making it versatile for landscapes, as well as for city and street photography. If you are thinking about which one to get first, this would be a good starting point.
Blue filters are not so commonly used as their benefit can be limited to foggy days, hazy areas, or autumn/winter days where the mist is common or snow is your subject. Blue light is governed by the phenomenon known to the law of physics as Rayleigh Scattering. In short: it is what makes the sky blue.
But let's not digress too much here. You should be aware that the washed-out effect of the blue filter is influenced by this law, consequently even if it should darken all the complementary colors, such as yellow, oranges, and red, it will not accomplish this purpose, so it is not recommended in the majority of the cases that you might encounter.
When you look at them in sequence, you clearly see the different filters spark a contrast between the colors. Once you have decided on the final look you wish to have, based on location, subject matter and so on, it's a matter of choosing what best serves your creative vision.
Which one is your favorite filter? Have you ever used any in your black and white photography? Share your experience in the comments bellow.