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       Wednesday, July 30, 2014 

 

Scanning Guidelines


This page will answer questions you may have about acquiring your figures with a scanner. There are a few things to consider before you get under way. Check these links for information concerning figure scanning. Please e-mail digitalart@cadmus.com for any additional information.

 

Scanning in Adobe Photoshop

Step 1: Test and Compensate for Scanner
Step 2: Compensating for Press Conditions

Scanning Tools/Resources

Other Helpful Hints and Information


 

Resolution Reminders

 

Line art should be scanned at 1200 dpi and saved in bitmap/monochrome mode.

Gray Halftones should be scanned at 300 dpi and saved in grayscale mode.

Color Halftones should be scanned at 300 dpi and saved in CMYK mode.

Combination halftones should be scanned at 600 dpi and saved in grayscale mode.

 

Please Note

 

An image should be saved and submitted in the size at which it will be printed (see a printed journal for column width or contact the editor). All cropping and manipulations must be completed before the images are submitted to Cadmus. If halftones must be reduced at Cadmus, the probability of introducing moiré patterns increases. Scaling, rotation, and cropping should be done at the scanning or imaging stage (i.e., in Adobe Photoshop) rather than in a page layout program. Make sure all images are clean by removing dust specks, scratches, and tape marks.

 
   
 

Scanning Black & White
images in Adobe Photoshop

STEP 1: Test and Compensate for the Scanner

This process requires a 12-step printers' grayscale. You can get one through one of the resources below or through a local graphics arts company or art store.

  • Scan the 12-step grayscale

First, scan the grayscale. Once the scale appears on your screen, choose the Show Info command from the Window pull-down menu.

scan1.gif (1731 bytes)

  • Read Highlight and Shadow

Position Photoshop's Eye Dropper tool over steps 1, 3, 6, 9, and 12 of the grayscale (noting the readings of each step in the info window). The info palette should show readings of 0, 25, 50, 75, and 100%, respectively. If your scanner does not read these gray values correctly, a curve may need to be created to achieve the correct tonal values.

  • Creating a Curve to Compensate for Scanner

To create a curve, choose the (Adjust->Curves) command from the Image menu. A new window with a curve will appear. At the bottom right of the curve you will notice the Input and Output information displays (Item #1 below). Click once on the grayscale at the bottom of the curve window (Item #2 below). This will change gray level readings to a percentage. (Note: if after clicking there your readings do not show a "%" symbol, you should click again. Your readings should have a "%" symbol.) Adjust the curve so that the steps on the scanned grayscale read 0, 25, 50, 75, and 100% at 1, 3, 6, 9, and 12, respectively. Then save this curve as Grayscale Curve in an easy access location. This curve can be applied to all scans to compensate for the scanner's deficiencies.

    This curve is designed as a general compensation to provide good quality scans from your personal scanner. The curve should be applied to all scanned images as a compensatory measure.

  • Loading a Curve

To load a Curve you previously saved. Scan or open an image and open the curve window (Image>Adjust>Curves..). Then choose Load... and navigate to the curve you previously saved. The curve will then be applied to the image.


STEP 2: Compensating for Press Conditions

  • Analyzing Highlight and Shadow Dot Percentages

The grayscale curve can be modified to compensate for press conditions, maximum and minimum dot, and dot gain to reflect the press requirements. To determine if any additional adjustments need to be applied to your image, first open the Info palette. Next, use Photoshop's Eye Dropper tool to read the image's lightest and darkest points.

The highlight dot, the lightest area of the image, should not be less than a 4% dot, shown below on left.

The shadow dot, the darkest area of the image, should not be darker than a 94% dot, shown below on right. If your highlight and shadow values are outside those ranges, you will need to adjust the image.

(To access the curve palette, select Image->Adjust from the pull-down menu and select Curves. The curve window will appear.)

  • Adjusting the Curve

Select the point at the lowest end of the curve (the highlight dot). Upon moving the dot, you will notice that the values in the Input and Output will begin changing. The value should increase by the amount of the difference between your smallest percentage and 4%. For example, if you read a highlight value of 1%, you will need to click on the lower left side of the slider, and move it so that the Input value reads 0%, and the Output value reads 3%. (Thereby changing a 1% value to 4%.) Do the same for the shadow dot, moving the 100% Input value so that the Output decreases by the amount of the difference between your highest percentage and 94%.

Adjusting the Highlights (below)

Adjusting the Shadows (below)

Adjusting the Midtone (below)

The midtone range can also be adjusted if needed. This can be done by selecting the middle of the curve (see below). The Input and Output values should read 50% and 40%, respectively. Be careful when adjusting the midtone dot; too much or too little adjustment can easily degrade the quality of the image. Generally it is better to slightly adjust the image than it is to over adjust it.

 

Scanning Tools/Resources

  • Scanner Calibration Tools
Pitman Prepress
STO Cameraman's Guide 12-Step Reflection
Item #1553-R1215
List Price is $6.75
Los Angeles (626) 855-1220
San Francisco (510) 265-5570

Kodak Professional Imaging Ordering Desk
Q-13 Reflective Grayscale strip
Catalog #152-7654
List Price is $20.70
2-3 day delivery
Toll Free: 800-234-0426

Other Helpful Hints and Information

  • Keep a Backup

It is a good idea to save and maintain an unedited version of the original scan in case you make a mistake in editing the image. Keeping a copy of the untouched image will save time if you need to rescan or recreate the image.

  • Treat Each Scan Individually

Always keep in mind that halftone photography and scanning is an art form. Each individual image differs in tonal range and contrast. Therefore, no one curve can achieve perfect or even good results for every scan. Each image must be viewed, adjusted, or "tweaked" based on its individual characteristics. Fine tuning of the curve and use of other features such as sharpening or unsharp masking may be required.

  • Practice Makes Perfect

If you are going to use Adobe Photoshop to generate or adjust images, it would be a very good idea to receive some formal training in its use. At the very least you should read the manual and practice on some test images.

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