subtractive color theory

Photoshop 6 Scanning using ICC Profiles

Working with Profiles
Applying Neutrality
Guidelines for Highlights, Shadows and Midtones
Adjusting Midtones
Conclusion
Typical Photoshop Neutral Balanced Values for CMY and RGB

1. Set up the Photoshop Pre-adjustments:
Adjust the color settings:

• RGB Working Space - For print use Adobe RGB or ColorMatch RGB
• CMYK Working Space, insert a printer profile
• Measuring Tools: use the Info Palette and Eyedroppers for Levels & Curves

2. Use the Photoshop Import to capture the image
If your scanner does not have a place to insert a profile then use the Mode/ Assign Profile option.

Viewing Tip:

When in the RGB mode use the View Menu/ proof setup to view the potential results of a CMYK conversion before you go to CMYK. Choose your CMYK working space profile and the rendering intent. This option allows you to have multiple view of the same image with different working spaces, profiles and rendering intents.

3. Use: Mode/ Assign Profile - Use your Scanner Profile
(this sets the scanner profile as the images source)

4. Use: Mode/ Assign Profile - Use your RGB Working Space profile
(this sets the working space profile as the images destination)

5. Adjust Highlight areas with Levels or Curves while in the Working Space. Use neutral CMYK target values via the Color Picker with RGB images.

Typical values are:

• Cyan =5%
• Magenta =3%
• Yellow=3%
• Black =0%

6. Adjust the Shadows with Levels or Curves while in the Working Space. Use neutral CMYK target values via the Color Picker with RGB images. CMYK shadow point values are based on the profile and will vary.

7. Adjust the Midtones with Levels or Curves while in the Working Space. These adjustments are based on image class (hikey/lowkey) and neutrality for midtones

8. Adjust the RGB image with Hue & Saturation or Selective Color.

9. Apply USM* - This step is an option and can be applied at other stages of imaging
process such as: either right after scanning (step #2) at this stage (step#9) or
after the image becomes CMYK ( after step #10).

10. Convert from the RGB Working Space to the CMYK Working Space.

Option A: Use the Mode / CMYK
Be sure the correct CMYK Printer profile is in the Color Settings

Option B: Use Mode/Convert Profile
Use your CMYK Printer Profile

11. Fine tune the CMYK image by adjusting
Highlights, Shadows, Midtones and Hues

Working with Profiles

Using canned or supplied profiles do not always work. We suggest using custom profiles that you or a service provider has made for your specific input and output devices.

Profiles are used in pairs. This means there is a source profile and a destination profile.

For example if your scanner does not have a place to insert a profile then you must use the Mode/ Assign and Convert to Profile option.

Assign: To your scanner profile
(this sets the scanner profile as the images source)

Convert: To your RGB Working Space
(this sets the working space as the images destination)

When you print or Mode/ CMYK, the source and destination change.

Photoshop 6 makes this easier than Photoshop 5.

Use Convert to Profile.

This dialog shows you the source profile of you image and then allows you to convert to your profile.

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Applying Neutrality to the Image -
Color Casts :A Fact of Life

Most all color images have some type of color cast and it is sometimes difficult to decide how to adjust color casts in highlights, shadows, and midtones of each original. Some color casts are slight and some dramatic. Color casts can be overcome by adjusting the color image either during the scanning, on the desktop color separation process or a combination of both.

Typically, neutral gray values are determined by the operator. See the neutral gray values chart below as a guide. The operators makes critical decisions about how neutral to make highlight, shadows and midtones by measuring and looking at each image. For example, if the image is going to print, neutral gray halftone output values are referenced to determine how neutral gray highlights, shadows, and midtones will become in the reproduction. If a color cast is in the image, the operator decides how much of a color cast to maintain, practically reduce, or completely eliminate it. This skill is learned by looking at the final results and remembering the RGB and CMYK halftone values that produce certain visual results.

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Guidelines for Highlights, Shadows and Midtones

Neutrality is a good guide for determining where and how to adjust highlight, shadow, and midtone areas from the start of the image reproduction process.
Adjusting the image to reflect the proper highlight and shadow range is a critical step in achieving a good quality color reproduction. This process frames the images so that the tonal range can be adjusted to give the best results in the reproduction.

o Identify the highlight areas of your image first.

Find a neutral white area that carries the whitest image details. This is called the diffuse highlight. Use target values of;

• Cyan =5%
• Magenta =3%
• Yellow=3%
• Black =0%

Identify the shadow areas second.

Find the darkest neutral black of the image area. Setting the shadow with Photoshop can be precarious if you have never done it before. What makes it so tricky is that different CMYK shadow point values are based on the Color Settings/CMYK Setup or ICC profiles. So the values in the Shadow Point Color Picker will vary. My suggestion is not to worry about the CMY values and only change the K value. The K % value can be adjusted to change how light or dark the shadow point becomes. Start experimenting with the default K value and then see the results. If the image comes out too dark in the shadow, then change the k value in small increments such as 5% until the images shadow areas do not reproduce too light or too dark.

Levels and Curves are the most common Photoshop tools to adjust an image's highlight and shadow areas

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Adjusting Midtones (the basics)

Image areas ranging from highlights to shadows define midtone image areas.
After highlights and shadows are set correctly, it is the midtones that control an image's contrast. Typically, when an image's contrast is set correctly then other image processing corrections such as altering gray balance and selective color usually become less likely and if necessary easier to adjust.

After the highlight and shadow areas are established, midtones have to be adjusted. Typically you can make a single point midtone adjustment with either the Levels or Curves tool. The Curves tool, however, allows multiple points of control over the adjustment of tones between the highlight and shadows.

Midtone adjustments are based on two factors:

(1) How the images tones are visually distributed throughout the image.

For example and average image is has a wide range of tones that extend from the highlight to the shadow. A light looking images tones (highkey) are predominantly in the lighter areas of the image. Dark looking images tones (lowkey) are mainly in the dark regions of the image.

Since there are varieties of light and dark image categories, only experience will indicate how much to change the color controls to optimize various types of light and dark images.

To understand how to adjust and deal with light and dark images, it is necessary to first to establish how an average image is reproduced. (i.e. establish the average image parameters). The average image parameters establish a starting point for reproducing all types of color images. The average setup is based on reproducing most average original images with little modification. To use this strategy highlights and shadows are defined and adjusted with little change and are applied with standard midtones settings, pre-established neutral values and hue and saturation (color correction) values.

Once color scanning and Photoshop parameters for average images are identified, the approach is to use them as a starting point to adjust light and dark images.

After highlights and shadows are adjusted:

• A high key image requires increasing midtone areas to bring out or better separate the highlight to midtone details.
• A low key image requires decreasing midtone areas to bring out or better separate the shadow details.

Since each image has its own unique distribution of tones, only experience will provide exactly how much to adjust a midtone, but the principles of adjusting midtones for average, light and dark images are the basis for achieving good contrast in a color reproduction for print or non-print workflows.

(2) If the image midtone areas need to become neutral gray looking

See the neutral gray chart below

Levels and Curves are the most common Photoshop tools to adjust an image's contrast and neutrality.

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Conclusion:
When highlight, shadows and midtones are set correctly the lightest and darkest near neutral image areas will visually help make the reproduction look like the original. If highlight and shadow areas are not adjusted correctly each reproduction will be inaccurate visually.

Color Areas
Color areas are seen as hues in original images and reproductions by a variety of objects or scenes. These areas are made up of colorful range of tones and hues in areas like red, green, blue, cyan, magenta, and yellow. Though generally not characterized by highlights shadows and midtones, color areas are directly affected by highlight shadow and midtone adjustments. Color areas are usually thought of and controlled in terms of selective areas such as red, green, blue, cyan, magenta, and yellow(RGBCMY).

Selective Color
The purpose of selective color correction is to control specific hues and/or the amount of saturation in each color area individually of a selected color RGBCMY.
While there are other methods of selective color correction, such as using masks, the system of using six colors area and four different color inks (making a possible 24 interactions) is the most well know method of selective color correction for scanners and desktop color software applications.

Hue & Saturation and Selective Color are the most common Photoshop tools to adjust an images selective color areas.

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Typical Photoshop Neutral Balanced Values for CMY and RGB

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