Contrast part 2: Tonal & Color Contrast

Part 2 of a continuing new blog series

“All About Image Contrast for Photographers”

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Contrast comes in “two flavors”

1. Tonal contrast

2. Color contrast

Each plays inter-related but separate roles

In determining how & what we see

 

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Color & Tonal Contrast

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The separate roles of tonal & color contrast

Greatly simplified –

Tone’s role is determining location & motion of what we see

Color’s role is identification (what it is that we see)

These functions take place in different parts of the brain

Each function using separate neural paths

The What (color) Pathway and

The Where (tone, brightness) Pathway

A side note – the part of your eye (cones) responsible for color

Doesn’t function in low light (when it’s dark)

So? Your night vision is all black & white!

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An application of  the What & Where to imagery

Talented artists can create paintings where

Object tones are nearly equal (equiluminant), but

Hues of the same objects differ greatly

Here is my favorite example –

Monet – Impression: Sunrise

Note the sun vs. its background

Wildly different hue, but

Equiluminant

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So Monet could create “equiluminance” – so what?

If an object and background are equiluminant,

Our “where system” can’t determine the object’s position

Why can’t the position be determined?

The where system is based on seeing tonal contrast

If parts of an image are equiluminant, there is no contrast

As a result, positions may seem to shift or shimmer

This is because each time your eyes re-scan that spot

Your vision may “compute” a different location

This is why Monet’s paintings (and others, as well)

Sometimes appear to have movement or shimmer in them

They confuse our where system & its need for tonal contrast

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So how about color & the “what” part of the equation

Color assists in visual discrimination

It helps detect patterns that might go unnoticed without it

Equiluminant stripes of different hues for example

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Together with tonal variations

It sharpens contrast between parts of an image

It is of little help with spatial details

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Hopefully, this shows how tonal and color contrast affect images

This information tells us how we can improve our own images

Both during image capture and in post-processing

Mastery of contrast, IMHO, is what made Ansel Adams stand apart

Specifically, his mastery of tonal contrast

(and not his camera technique which, though obviously good, didn’t “stand out from the crowd”)

Master tonal & color contrast and you too will stand out

The next post will discuss, in general, how this can be done

Followed by detailed post-processing examples, including

How to introduce equiluminance into your photos

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If you’re interested in learning more, I recommend

Vision and Art: The Biology of Seeing [Paperback]

by Margaret S. Livingstone

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