Filtered BW Conversions

Posted by CWade in How-To | 2 Comments

Okay, filters. Filtering black and white images is one of the most gratifying concepts/processes in photography (IMO), so I thought I’d show some different results.

Disambiguation: I’m mostly referring to contrast-enhancing, colored, filters.

To be clear, this isn’t meant as a tutorial, but here are some I enjoy for both Photoshop and GIMP:

I first became acquainted with filters in their tangible form: physical glass or plastic pieces placed in front of the lens to filter incoming light (most often used in film photography.) I use the Cokin system with my N80 when I shoot black and white film. However, I’ve had good success using them with my D80 as well, even though most photographers prefer to convert color–>BW digitally.

This .gif example of Lu-dog demonstrates how the two most commonly-used colored filters affect the BW conversions.
  1. Frame 1 = Color original
  2. Frame 2 = strong Green Filter
  3. Frame 3 = strong Red Filter

A good, semi-mnemonic way to remember how filters will affect your image: filter color will lighten similarhues in the image & darken complementery hues. You can
refer to your basic color wheel for reference:

So you can see that a red filter (Frame 3) will lighten the red tones (look at the carpet on the
left of canine), and darken the cyan tones (carpet on right of canine).

I should mention there is no “correct” result. It’s all subjective, right? The green filter yields a generally more contrasty image in this example, and the red filter tends to isolate the subject (Lu-dog) a little more from the carpet.

Personally, I prefer the color image, here. Go figure.

As an outdoor example, my neighbors have some awesome tulips I’m obsessed with:


Green Filter

Orange Filter

Red Filter

Here, my favorite is the last, the
red filter. I like how it isolates the flowers from the greenery. But again, this is personal preference.

One more example, just for kicks:

From left-right, you can observe the tube gain contrast value, while the stripes on the barricade lose contrast value.

The green filter in the first absorbs much of the greenish light being reflected by the hose, and so it appears white. By the same token in the first image, the filter is letting much of the red UV spectrum, reflected by the barricade’s reddish-orange stripes, through to the camera’s sensor. In the last image, which has been red-filtered, just the opposite is true. (Also, notice the grass has an increased contrast value.)

Again, this is an image I’d probably never want in BW to begin with.

Of course, the most often-used photographic application of contrast-enhancing, color filters is in landscapes: making white clouds stand out in a bright sky.

Here is an example, “Orange Hill,” which can be found in my online portfolio:

It usually ends up looking something like this (red-filtration):

Compare, side-by-side, with a version that’s simply been desaturated without filtering:


2 Responses to Filtered BW Conversions

  1. Matt Allen Photography says:

    awesome write-up Cait!

  2. gretchenmist says:

    great post, thanks for sharing your know-how. i never think of photoshop from a photography point of view!! when i know i should coz then it all makes more sense!

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