Looking at PS Color Management from Frequently Occurred Problems in Prepress Enterprises (Part Two)

What should I do when I open an RGB image with a profile embedded in it and the embedded profile is not the same as the color currently set in Photoshop?

If you select “Do not convert”, the image data will not change, but the color of the image on the display may change significantly; if you select “Conversion”, the image data will change, but the color of the image display may not be much different from the previous one. . Selecting "Convert" normally has better results, so it is recommended to "Automatically convert" or "Ask at opening".

You can do it in Photoshop 6. X uses "keep the built-in profile" so that the image is still displayed according to the built-in profile, which is a convenient way for RGB images that are eventually converted to CMYK mode. Do not use this menu if the RGB image is still in RGB mode at the end.

Note: Due to the inconsistency between the image-embedded ICC profile and the setting in Photoshop, the feature file mismatch dialog box appears when the image is opened in Photoshop. Normally, the conversion is selected.

4) RGB image file without a profile

If an RGB image file is not embedded in the property file, under normal circumstances, you can select a feature file most frequently used by the operator in the "From" drop-down menu in the open file prompt box, and select the corresponding in the "To" menu. CMYK or RGB mode.

5) CMYK scan data with profile

If you get a batch of scanned images while the scanner operator tells you the color separation settings for the scan, or provide you with the appropriate ICC profile, you can do this in CMYK Settings or CMYK Work Color Space. Make settings.

Note: In the CMYK setup menu, you can select or set the profile that matches the scanner. This will give you a better screen display.

From this point, we can also extend it slightly. We can sweep the image into RGB mode when the scanner scans. With the help of the ICC profile, we can use the same separation on each computer, whether it is a PC or a MAC. Setting, because sometimes image correction with RGB images has advantages over CMYK, such as using all filters. The RGB image is converted into a CMYK image before the final output; the same unfamiliar RGB image can be separated using a common separation property file. Many are avoided due to the uncertainty created by using the Photoshop Color Settings menu!

6) CMYK scan image without profile

If you get CMYK scanned images without a profile, no matter how good the quality of these images, you have to continue processing in Photoshop, which is often the situation in prepress companies, because these images are already in CMYK mode, You can try to use the cancel color management feature, which is to choose "do not embed profile" in Photoshop 5.X, and this option is stored in Photoshop 6.x.
The purpose of this setting is to protect the image colors. If you do not cancel the color management function in Photoshop and select the wrong Phot-oshop feature file will lead to wrong color conversion!

7) CMYK image with "error" profile

In principle, as with the aforementioned RGB image, “Conversion” is usually selected. The color loss caused by the conversion between CMYK and CMYK is not as severe as the conversion from RGB to RGB.

One thing to note here is that the different profiles of CMYK images (including grayscale images) determine the number of different blackplates. For example, when the grayscale image is converted to a CMYK image, different separation methods (characteristic files) are used. Produce a different number of black editions; for example, if a CMYK image uses a GCR color separation method with a higher number of black editions, if the color is not directly matched when a mismatch occurs, all of this information will be lost! It is better to choose "Question when opening" for the above mentioned situation. This allows you to see what kind of profile the CMYK image embeds when you open the image. You can also select "Do not convert" to open the image to see if the image meets the output requirements and correct it manually if possible.

There is a new feature in Photoshop 6.X, “Preserve embedded profile.” If you select an image that does not match the open profile, the display will be displayed according to the image's original embedded profile, such as with a profile suitable for gravure printing. The image previews the actual effect of gravure printing on the display; images with a file suitable for newsprint print characteristics preview the actual effect of newsprint printing on the display.

8) CMYK image files without profiles

For a CMYK image without a property file, you can specify a hypothetical property file. For image files that were saved long ago (such as Photoshop 4.0 does not support property files), you must specify a hypothetical property file before you convert it.

4. Summary

Using the color management options in Photoshop makes it easy to achieve the following main goals:

Improve the quality of the image;

The monitor display in a working group is definitely inconsistent. Using RGB profiles allows the images to be nearly identical on different displays!

The same CMYK image in a working group is certainly not consistent on different displays. These problems can also be solved with the device-independent ICC profile!

Images can be exchanged between PC and Mac with minimal color loss;

An image can be converted through different ICC profiles, so that the same image can be applied to different output processes;

A cheaper printer can be used as a digital proofing device. Although there are different RIP solutions for color management, the prices are relatively expensive. Some color management functions in Photoshop and other software can use inexpensive ink-jet printing to obtain proofs that can preview the final print. This is at some price. The expensive color management workflow cannot but be said to be a daunting challenge!

Source: HC Network Printing Industry Channel