Finding lightest and darkest areas

In my digital darkroom workflow, one of the things I commonly do is find the lightest and darkest parts of the subject.  I sometimes also locate a medium toned, neutral color, if available.  I do this for a number of reasons.  If an image has a color cast, we can use this information to remove it using the Levels or Curves adjustments.  Also, while we make tonal adjustments, we can monitor these locations to see if we are losing detail.  This section covers the method I use to find the lightest, darkest and medium toned areas.  We will be using Figure 1 as the example image in this section.
 

Figure 1

Looking at Figure 1, we can see this image has whites and blacks.  However, the whitest white is the bit of sky in the upper right hand corner and the darkest black is the deep shadows above the white fronds on the right side of the image.  These two areas are not in the same light as the rest of the image.  Therefore, these two areas are not the ones I am looking for.  What we want to do is identify the lightest and darkest parts of the image that we consider part of the subject.  Not the specular highlights or deep shadows.

Another thing we will notice is this image has a strong bluish cast that we will want to remove.  We will be removing this color cast in the sections discussing Levels and Curves.  However, we first need to identify appropriate light, dark and neutral areas we wish to adjust.  In this image, when we search for the lightest areas, we will look in the area of the white fronds at the bottom of the image.  When we search for the darkest area, we have lots of options, but we want to avoid the dark shadows.  A good place to search for a medium toned, neutral color is in the bark of the nearest pine tree.

Lightest and Darkest Areas

To find the lightest and darkest parts of the subject, we will use the Color Sampler tool in combination with the Threshold command.  When finding the lightest and darkest areas, it is important to remember that we need to find the lightest and darkest tones that we consider an integral part of the subject.
 

Color Sampler

To find the lightest and darkest parts of an image, follow these steps.

• Select the Color Sampler tool .  As seen in Figure 2, it is in the Adobe Photoshop Tools palette.
• Change Sample Size to either 3x3 average or point sample.  I usually use 3x3 average as point sample can be too precise to use.  Sample Size is in the Photoshop menu bar.
• Turn caps lock on to change the Color Sampler cursor to crosshairs .
• If there are other layers in the Photoshop document, make sure the image layer is the active layer.
• Click Image > Adjustments > Threshold.
• Move the Threshold slider to the left to find the darkest area of the image. Shift - click this area.  We have now created a Color Sampler target for the dark part of the image.  Figures 3A and 3B show how the Threshold command works.
• Now move the Threshold slider to the right to find the lightest area of the image, as shown in Figure 3B.  Shift - click this area to set another Color Sampler target.
• Cancel the Threshold dialog box.  Do not click OK.

I chose the dark side of the pine tree in the middle of the image as the darkest area and one of the fronds as the lightest.  When creating the color sampler targets, the important point to remember is we are not trying to find the lightest and darkest part of the image.  We are finding the lightest and darkest areas of the subject that we wish to monitor.

Figure 3A.  Using the Threshold Command to Find Darkest Area

Figure 3B.  Using the Threshold Command to Find Lightest Area

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Info Palette

When creating a color sampler target , Photoshop places its information in the Info palette.  Looking at Figure 4, we can see at the bottom of the Info palette is #1 and #2.  This corresponds to the numbered targets we just created.  The RGB values are showing us the individual red, green and blue channel values.  If the image areas we targeted were truly neutral, the three RGB numbers would be the same.  Looking at target #1, which was placed on the white frond, we can see that the green and blue channels are the dominant channel.  This tells us this area has a cyan color cast to it since green + blue = cyan.  Target #2 is showing a definite blue cast since blue is 15 and red and green are both 0.

We have finished identifying the lightest and darkest areas.  Now we will identify a mid toned area.
 

Mid toned Area

To find a mid toned area of an image, we will use the Color Sampler Tool in combination with the Curves control.  This target can be especially useful when using the gray eyedropper in the Levels or Curves control when neutralizing a color cast.  If the mid toned area will be used to help remove a color cast, it is important to find an area of the image whose color we want to be neutral after correcting.  In our image in Figure 1, pine tree bark represents a color that should be neutral.  So we will look for a mid toned area there.

 

To find a medium toned area of an image, follow these steps.

• Turn caps lock on to change the Color Sampler cursor to crosshairs .  (The Color Sampler tool does not have to be active at this time though.)
• If there are other layers in the Photoshop document, make sure the image layer is the active layer.
• Click Image > Adjustments > Curves.
• Click-hold the left mouse button and mouse over the image in the area where we think we will find the mid toned value we want.  As we mouse over the image, observe the Input/Output values in the Curves dialog box.  Once we find an area as close to 127 as possible and it is a color that should be neutral, stop moving the mouse.
• Hold down the Shift key and click the left mouse button once.  We have now placed a third color sampler target over our mid toned area.  All three color sampler targets can be seen in Figure 5.
• Cancel the Curves dialog box.  Do not click OK.

We have now finished identifying and targeting the lightest, darkest and medium toned parts of the subject.  Figure 6 shows the Info palette with all three color targets.