Scanning tips

You can find tips on scanning in general here.

You can find tips on scanning for print here.

Tips on scanning for the web.

Color: You would usually want to scan at full color(24 bit).

Resolution: You have 2 main choices as far as what resolution to scan at for an image going on a web page.

You can scan at a higher resolution than you need. This gives you the flexibility to resize the image down to the size you need later. You then might need to sharpen the image afterward using he unsharp mask filter(see below).

If you know exactly what size you need beforehand, you could scan at the exact resolution you need to get the image at the size you want for your web page. To figure out the resolution to scan at for a web page, you can use the following formula.

For example

200/4=50

Your scanning resolution is 50 ppi(pixels per inch)

Moire Patterns

If you get a moire pattern from your scan, there are a couple of ways to repair them, but your better off avoiding them in the first place.

Moire Patterns are not an issue when scanning photos printed traditionaly(not with ink).

To avoid moire patterns:

1. Look for a descreening filter in the scanning software.
2. Try a different scanning resolution(probably higher).
3. Angle the print on the scanner a little.
4. Scan at a higher resolution and then downsample.

General Steps to correct and prepare images for screen or print
Some steps can be optional.

1. Straightening and cropping
   1. Use the ruler tool under the eyedrop tool to correct tilt.
      1. Drag along what should be horizontal or vertical like the horizon or a building.
      2. Go to image-image rotation- arbitrary to rotate to straight.
      3. You can also rotate while cropping if you put your cursor near the corner of the crop tool marks.
   2. Use the crop tool to crop.
      1. Get this C key on your keyboard to choose the crop tool.
      2. Hit the enter key to accept the crop, or the escape key to start over.
2. Spotting, retouching, dust and scratch removal.
   1. For spotting, the spot healing brush usually works well.
      1. Pick a brush at the top that is slightly larger than your spots.
3. Brightness and contrast/Global tonal correction
   1. For a quick adjustment of conrast, use a levels adjustment layer
      1. Click on the adjustment layer button at the bottom of the layers panel and choose levels.
      2. Drag the black-and-white sliders under the Histogram in towards the center until you get to an area of the histogram where there is some image data.
4. Correct colors/saturation/Global color correction
   1. One way to do a color correction in your image is to use the gray eye dropper tool in a layers adjustment layer and click on something in your image that should be gray.
   2. Another way would be to go to the channels menu in the levels adjustment layer, and drag the center slider in each channel to adjust the color balance.
5. Selective tonal and/or color correction
6. Sharpen
   1. Sharpen using the unsharp mask filter under the filter menu. See below for a description of the settings for the unsharp mask filter.
7. Suppress noise and artifacts
   1. This might be necessary if you took a photo using and high ISO setting, or you were trying to fix a JPEG that had been overly impressed.
8. Target for print (sharpening, handling out of gamut colors, compressing tonal range, converting to CMYK.)
   Or
   Optimize for Web

Unsharp masking, or USM, is a traditional film compositing technique used to sharpen edges in an image. The Unsharp Mask filter corrects blurring introduced during photographing, scanning, resampling, or printing. It is useful for images intended both for print and online.

The Unsharp Mask filter locates pixels that differ from surrounding pixels by the threshold you specify and increases the pixels’ contrast by the amount you specify. In addition, you specify the radius of the region to which each pixel is compared.

The effects of the Unsharp Mask filter are far more pronounced on-screen than in high-resolution output. If your final destination is print, experiment to determine what dialog box settings work best for your image.

To sharpen an image using the Unsharp Mask filter:

1 Choose Filter > Sharpen > Unsharp Mask.

2 Sharpen the image:

• For Amount, drag the slider or enter a value to determine how much to increase the contrast of pixels. For high-resolution printed images, an amount between 150% and 200% is recommended.

• For Radius, drag the slider or enter a value to determine the number of pixels surrounding the edge pixels that affects the sharpening. For high-resolution images, a Radius between 1 and 2 is recommended.

A lower value sharpens only the edge pixels, whereas a higher value sharpens a wider band of pixels. This effect is much less noticeable in print than on-screen, because a 2-pixel radius represents a smaller area in a high-resolution printed image.

• For Threshold, drag the slider or enter a value to determine how different the sharpened pixels must be from the surrounding area before they are considered edge pixels and sharpened by the filter. To avoid introducing noise (in images with fleshtones, for example), experiment with Threshold values between 2 and 20. The default Threshold value (0) sharpens all pixels in the image.

If applying the Unsharp Mask filter makes already bright colors appear overly saturated, convert the image to Lab mode and apply the filter to the L channel only. This technique sharpens the image without affecting the color components.