How to Do Everything With Your Scanner- P11 pdf

Be Sure to Look at the Optical Resolutionof a Scanner Optical resolution is the most commonly used specification to compare the capabilities of different scanners.. Generally, the higher

Be Sure to Look at the Optical Resolution

of a Scanner

Optical resolution is the most commonly used specification to compare the capabilities

of different scanners It refers to how many pixels, dots, or samples per inch the scanner’s sensors can detect Generally, the higher the resolution, the better the quality

of the scanned image Low-end scanners have a resolution of 300 ppi, while high-end scanners can detect as many as 4,000 ppi

The 300-ppi variety will provide adequate resolution for computer-screen images, since most computer graphics cards can’t handle much more detail than this (You can learn more about how a graphics card functions in Chapter 4.) On the other hand, if your objective is a nice copy from a laser or color printer, the results from a scanner with a 300-ppi optical resolution are likely to disappoint you A 400 to 600 resolution will probably give you the quality you’re looking for in a printed copy

Optical resolution is most important when you need to print good-quality photos to include in publications such as books, magazines, newsletters,

or scrapbooks If you need good-quality printed photos, choose as high a resolution as you can afford Economize with a lower optical resolution

if you’re producing images to be viewed on a computer monitor or in PowerPoint presentations.

Avoid Comparisons of Interpolated Resolution

Suppose you have a choice of two scanners in your price range, one advertising a resolution of 300 dpi (or spi or ppi) and another boasting a 600-ppi resolution The 600-ppi resolution is a better deal, right? Not necessarily

A recent trend has been for manufacturers to market their scanners based on

interpolated, or software-enhanced, resolution Based on some technical guesswork,

interpolation uses a mathematical algorithm to add more pixels to the ones the scanner has sampled with its sensors The result is an image with more pixels or dots per inch, but not necessarily more accuracy as to detail

Interpolated resolution produces good results for images on the Web, but is less satisfactory for scanning photographs for archiving or publication Generally, it is not a good option if you need to scan negatives, since negatives require a resolution capability of at least 1,200 ppi

When comparing the resolution of various scanners in your price range, make sure you’re comparing apples to apples Do not compare the optical resolution of one model to the interpolated resolution specifications

of another.

Testing the Tonal Sensitivity

Not all 30-bit scanners are created equal A scanner might be able to detect a large number of colors, but over a relatively narrow range Also, bit depth doesn’t tell you

how well scanners distinguish among similar shades This is called tonal sensitivity,

and is not disclosed by manufacturers Generally, high-end, more expensive scanners exhibit greater tonal sensitivity

You can evaluate the tonal sensitivity of different scanners by comparing the scanning results using the same original Skin tones are particularly useful for comparing tonal sensitivity between scanner models Certain models of scanners often cast a slight greenish tinge to skin tones, which can significantly alter the appearance of your subject.

Read the Manufacturer’s Resolution Rating

When you check the optical resolution of a particular scanner, you find it expressed in two numbers For example, a scanner might have a 300×600 ppi resolution, or a 400×800 ppi capability The first number refers to the number of pixels that can be sampled horizontally, and the second number specifies the vertical sampling

The number of samples for the vertical sampling is greater, but because of the blurring effect that occurs as the scanner moves vertically from line to line, not all of the sampled data is useful for reconstructing the image For this reason, when you are shopping for a scanner, it is most useful to compare scanners based on the their horizontal resolution, or the lower of the two numbers

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Coordinating Your Scanner with Your Printer and Monitor

An issue that causes constant confusion is that of coordinating the capabilities of your scanner with those of your printer and monitor to get the best final image Although your scanner might have the capability to detect large amounts of color data, your printer might not have the capability to print it, and your monitor likely cannot display all of it

Measuring the Monitor’s Resolution

Computer monitors have resolution specifications all their own, usually provided to you by the manufacturer in horizontal and vertical pixels A common monitor resolution is 800×600 pixels, or 800 pixels horizontally and 600 pixels vertically Another common monitor resolution is 1024×768

The higher the resolution setting on your computer, the more detail you can display from a scanned image on your computer screen In contrast, lower resolutions

do not make full use of all the image data your scanner might have captured

The Effect of Changing the Monitor and Scanner Resolution Settings

Increasing the resolution setting on your monitor makes images, such as the icons on your screen, appear smaller because the pixels display closer together The overall image at a higher resolution level is more detailed, and appears seamless Figures 2-6 and 2-7 show images displayed at monitor resolution settings of 1024×768 and 640×480, respectively

Higher resolutions—1024×768 or greater—usually work better on a larger monitor If you currently have a 17-inch monitor, you might want to invest in a 19- or 21-inch one if you plan on doing a lot of graphics work.

The effect of increasing or decreasing the resolution settings on your scanner also has

a marked effect on what you see on your screen For example, suppose you create two different scans of the same original image You scanned the first using a resolution of 600 ppi, and the second using 100 ppi, as shown in Figures 2-8 and 2-9 When viewed, the 600-ppi scanned image appears physically larger than its 100-ppi counterpart This is due

to the fact that while the original image was the same, the amount of pixel information

scanned and displayed has increased So, your monitor simply has more pixels to display.

FIGURE 2-6 An image displayed on a monitor set at a resolution of 1024×768

appears smaller.

FIGURE 2-7 An image displayed on a monitor set at a resolution of

640×480 appears larger.

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FIGURE 2-8 An image scanned at 100 ppi

FIGURE 2-9 An image scanned at 600 ppi