jnd: Just-Noticeable Difference

Part of a series – Color Managed Workflow

Today – Seeing differences between two colors

Summary – How much can colors differ (between monitor and print; between camera capture and post-processing displays, etc.) before you can notice the difference? This difference, jnd, may make or break your efforts to get correct image colors. This post illustrates jnd by comparing possible camera vs monitor color differences.

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I recently asked when is an image “good enough”

How  about a similar question

When is the match of two colors “close enough”?

Welcome to the world of jnd

(I’m not making up the acronym)

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Roll mouse over the image to see the after version

Shadow recovery in the cliff face

D300-_101004_155701__DSC7906_nx_lr5acrD300-_101004_155701__DSC7906_nx_lr5acr cep

Acadia National Park

DND (Definitely Noticeable Differences); I did make this one up 😉

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Note: Today’s color match question is somewhat related to

The recent post on Color IQ

BUT – different

The colored blocks in the IQ test

Were noticeably different in terms of hue

The test challenge was to put them in “hue order”

jnd addresses the related question of

How different must two colors be before

We even notice that they are different

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Without all of the color-geek-speak details –

Color differences can be measured & quantified objectively

Based on such measurements, tests with viewers established

How large the difference between two colors must be

Before the difference is noticed (subjective)

This is the jnd for colors

jnd also is used in other applications, e.g. music

Tests put the color jnd value in the range of

A color mismatch between 2.3 and 6

(I’ll spare you the details & illustrate this below;

suffice to say if the mismatch is above 6

Viewers will probably notice it)

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An Example

The example uses sRGB & Adobe RGB 1998 spaces for illustration

To remind you of how these two space compare

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Figure 1

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Fig. 2, below, shows jnd for sRGB vs Adobe RGB color spaces

So what?

Well, your camera typically will use one or the other

Your monitor most often also uses one or the other

Fig. 2 shows the difference between

What your camera captured and your monitor displays

WHEN these two devices aren’t using the same color space

Should you care?

I sure would!

If your post processing software reports

“Profile Mismatch” (or a similar alert)

When you open an image

This is what it’s alerting you to 😦

Click for Full Screen

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Figure 2

The horizontal bar near the bottom is the

Key for the differences shown in the main image above it

For example, the black square has a difference of 9 (very noticeable)

It’s the difference between the two space’s green

Look at Figure 1 to see WHY the large difference in greens

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Of course, the differences don’t have to be so noticeable

That’s where profiles enter the picture (a pun?)

The color differences in this “after profile” example

Range from 0 to 0.025, as compared to

0 to 9+ when we ignored the color space mismatch

Which would you prefer? 😉

8-2-2013 9-12-14 AM

Figure 3

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This is a tease for the next Color Management post

Profiles – what they are & what they do

In a few days after the glaze clears from your eyes 😉

I’m hoping to convince you that

You should know & care about color management

If you’ve learned something, pass it on….

This post illustrates my posting goal (not always achieved)

To provide useful photography improvement related information that won’t be found on hundreds of other sites; stand out from the crowd a little

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