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By Root 1822 0

or Perceptual CMM and the target CMYK output is a newspaper color supplement printed on uncoated paper. If you use the Absolute Colorimetric rendering intent to convert these ‘targeted’ CMYK colors to the color space of the proofing device, the proof printer can reproduce a simulation of what the printed output on that stock will look like. Note that when you select the ‘Proof’ option in the Photoshop print dialog, the rendering intent menu appears grayed out. This is because an Absolute Colorimetric rendering is selected automatically (although the Print dialog doesn't actually show you this) in order to produce a simulated proof print.

When levels have to be set manually

You should be aware that some repro companies operate what is known as a ‘closed-loop system’ where they edit files in CMYK and do not necessarily use a profiled workflow. This is something that may only affect high-end repro users of Photoshop and if this is the case, you may need to target the shadows manually according to the conditions of the printing press. The same is also true if you are editing a grayscale file in Photoshop that is going to print.

Fine-tuning the CMYK end points

You can use the black point and white point tools in the Levels or Curves adjustment dialogs to assign specific pixel values to the shadows and the highlights. Normally you can rely on an image mode conversion to adjust the shadow points for you, but there are certain situations where it may be desirable to fine-tune the endpoints manually, such as when you are working on grayscale images that are destined to be printed in a book, magazine or newspaper. It may also be necessary if the image is already in CMYK mode but is missing an embedded profile, but you know what the press output should be. Instead of relying on the profile conversion to assign the end points, you can assign these manually. The eyedropper tools can also be used to color correct an image and remove color casts from the shadows or highlights, plus the gray point tool can be used to assign a target gray color to the midtones (this was covered earlier in Chapter 5).

Let's now run through the basic steps for assigning the end points via the shadow point and highlight point tools. Before you do anything else, I suggest you select the eyedropper tool in the Tools panel and go to the eyedropper Options panel and set the Sample Size to 3 × 3 Average (or perhaps higher, such as 5 × 5 Average). Now open the Levels or Curves dialog. The default values for the shadow point and highlight point tools are 0% and 100%, but if you want to set the shadows and highlights in a grayscale or CMYK image for repro output, you will need to set these differently. The shadow point should obviously be higher than 0% (in order to take into account the dot gain) and may typically need to be set to 4%, while the highlight point for the non-specular highlights should be slightly darker than 100% (this ensures that the highlight detail will hold on the press) and should be set to around 96% or lower. This method of assigning the end points allows you to decide exactly where the highlight and shadow points should be. Bear in mind here that when setting the highlight clipping point it is only important to set the highlight clipping point to the value suggested here for the non-specular highlight areas, as was discussed earlier in Chapter 3 on pages 180–183. In the case of specular highlights, such as highlight reflections off metal surfaces, there is no need to worry about these being clipped to pure white.

1.

I double-clicked the highlight point tool in the Levels dialog box (circled blue) and set the highlight target value (circled red) to match that of the press. A brightness setting of 96% should be OK for most printing situations.

2.

I then zoomed in on the image and clicked on the area I wanted to assign as the highlight target point (this should be a non-specular highlight and not a specular highlight such as a reflection or glare).

3.

Next, I double-clicked the shadow point tool (circled blue)