5.3. CM and Scanning: In Depth
First, remember that the general rule of thumb is that the better the original image or scan, the better the quality of the output.
In this example, I will use the Epson Scan software with a Perfection 3200 scanner. Most other software works in a similar fashion; if you understand the concepts here, then you should be able to adapt them to your particular scanner. (Note that there are a few scanners, including the entire HP line, which are designed for the beginner or business user, which do not give you the controls to create a high-quality scan.)
So let's dig right in and set up the scanner. By default, the scanning software is in Full Auto Mode. There are a variety of options that are available if you go into the Customize options, including the type of original, the resolution of the desired output, dust removal and color restoration, and a few other features. Next to the Scan button (and not very obvious in our example) is the File Save Setting button, which allows you to select the location, file format, and name of your file.
The Home Mode is the next mode on the list, and it is a bit more advanced. Home Mode gives you considerably more options, including the Document Type that you are scanning. You are also asked for the Destination Document Type and the Output Resolution. The Configuration button at the bottom of the window brings us to a new window.
Finally, we are getting to the good color stuff. From the Configuration screen, click on the Color button, and you are presented with three options. Under the first option, Color Control, uncheck "Continuous auto exposure." If you leave this option on, the scanning software will take the lightest tone and make it pure white and take the darkest tone and make it pure black, which is a problem because we'll lose all the details in the highlights and shadows. Set the Display Gamma to the gamma that you have your monitor calibrated and profiled to.
The next option in the Configuration window is ColorSync on the Mac and ICM on the PC. This option allows you to apply a scanner profile to the scan and then convert it directly to your working space or, if you are not planning on editing the image at all, to apply the printer profile. For the most part, I would not use this setting, even though it looks cool, because it doesn't allow you to calibrate the scanner.
Last but not least, the third option is the No Color Correction option. This option would be used if you were planning either to apply your scanner profile or color correct your image in a program such as Photoshop. To obtain the best-quality scan with this option, it is best to scan at a high bit level.
Professional Mode is the third and most powerful scanning mode for the Epson Scan software. This is the mode where we're going spend the most amount of time, going through the many controls and options. As with the two previous scanning modes, we first need to determine whether we are working with reflective or transparent media. To scan transparent media, such as film, you either need a dedicated film scanner or a flatbed scanner that has a separate light source for the film.
In Professional Mode, we have an even greater number of options for Destination /Image Type. The two that we are most concerned with here are 48-bit Color and 16-bit Gray Scale. Earlier in the book, we spoke about the advantages of working with files with a higher bit depth. The concept of 48-bit color is a bit confusing until you realize that a 48-bit image contains three 16-bit files: one each for red, green, and blue (hence, 16 x 3 = 48-bit). Unless you are doing high production scanning with minimal to no corrections or enhancements in image-editing software such as Photoshop, you should scan at the high bit level, which will allow you to have the most tonal information with which to edit. After editing, you can convert the image into an 8-bit file.
The Adjustments give you a variety of options in the Reflective Mode, such as Unsharp Mask Filter and Descreening Filter. If we change over to the Film Mode, new options become available, including Grain Reduction, Color Restoration, and Dust Removal. Since our main concern is achieving the best color from the scanner, we won't go into detail about these options. If you need to find out more, see the Appendix for a list of books and manuals that cover some of options more thoroughly than we can here.
Our foremost concern is the Adjustments indicated by the four icons at the top of the window. In order to make these options available, you need to be in Color Control Configuration. If they are grayed out, then you have selected either the ColorSync or No Color Correction options.
The leftmost icon is for Auto Exposure, which we don't want to use because, as mentioned earlier in this chapter, it blows out the highlights and plugs the shadows. The second icon from the left is the Histogram Adjustment, which is where we will do the most work in calibrating the scanner. We'll also be using the next two buttons in part: Tone Correction and Image Adjustment.
A great tool that we can use to assist us in calibrating the scanner for reflective originals is the GretagMacbeth ColorChecker. This target has been around for many years, and the reason that it works so well is that there are a limited number of patches (compared to other targets), and it is easy to find out what the RGB values of the patches are.
The values in this chart are for the Adobe RGB (1998) color space because most photographers will use it as their default color space. By reading the RGB values of the ColorChecker in the scanning software and adjusting them to those in the Adobe RGB chart, we can calibrate the scanner.
The Histogram Adjustment window gives you a tremendous amount of control over the scanner. We will use this window to set the highlight, shadow, overall tonality, and overall color balance using the ColorChecker. A histogram is a representation of the number of pixels at any given point on the tonal scale. Black is on the left, while white is on the right. The value of black is 0, while white is 255. For our individual RGB channels, 0 is no color, while 255 is the pure color.
In the Histogram Adjustment window underneath the histogram, you will find a series of sliders for both input and output. The Input scale has white, gray, and black sliders; three eyedroppers for white, gray, and black; and a numerical readout for each. The output scale is much simpler, with only white and black sliders and readouts. By using these tools, you can go a long way toward calibrating your scanner.
Let's go step by step: