Production 2 - Scanners and Scanning

Scanning the Printed Grayscale Art:

Actually the same as scanning printed line art in that the grey areas have been converted to a dot pattern. ◦ All you have to do is capture the original dots by scanning as line art at the resolution of the output device. ◦ You are under the same constraint as with line art; ‣ You cant change the size of the image. ‣ Nor can you do any retouching in an image editing program because you will destroy the dot pattern

Scanning Coloured Line Art:

All line art is 1-bit when it is scanned or created, but all line art does not have to be printed with black ink. ◦ Many line art images have been printed with solid colours —perhaps a spot colour or 100 percent of a process colour — and you can still scan them as line art. ◦ Important thing to remember is that the scanner can "see" the colour. ◦ If the line art is a light colour like yellow, you need to increase the threshold setting so the scanner can pick up the light colour. ‣ Remember that you don't have to use black ink; you can print it with any spot colour. ◦ Scan the line art at the resolution of the output device, with a maximum resolution of 1200 PPI

Scanning Printed Line Art:

All you have to remember is that any gray areas you see aren't really grey — they're actually a pattern of dots. ◦ Scan a 1-bit, also known as line art. ‣ Solid black areas will appear as solid black and the dots will appear as dots. ‣ Shouldn't cause a moire pattern because you're not "screening a screen" — you're just copying dot for dot. ◦ One drawback to scanning printed art that has screens (dots) is that you cant change the size of the scanned image ‣ Enlarging causes the linescreen to become more obvious. ‣ Reducing causes the dots in the linescreen to merge together

Principles of Scanners:

An image is placed on a scanner surface and light passes across it. As the light hits the image or passes through, the light changes depending on what is in the image. Those changes to the light are then stored as a digital file. That digital file is called the scan, or the scanned image. A desktop scanner and a desktop printer are simply photocopy machines with very powerful computers in the middle to manipulate the images. Almost all scanners use the same CCD image sensors found in some digital camera. The more sensors in the scanner, the more information can be stored. The highest quality scanners use a technology called PMT (photo-multiplier-tubes) that read the CMYK colour values in the image and then translate that information into RGB data. ‣ Unless you've got a drum scanner, your scanner is CCD, not PMT. Choosing the right type for a project depends on the original image and what you intend to do with the image

Drum Scanners:

Highest quality scanner, the image (photograph, canvas, illustration, fabric, etc) is wrapped around a transparent cylinder. The cylinder rotates as the light is focused on the image. ◦ Can scan either reflective or transparent art. ◦ Can't use a drum scanner for images in books or art mounted on stiff illustration boards. ◦ Original drum scanners were extremely expensive machines that took up a portion of a room and needed specially trained operators. ◦ You took an image to the print shop and they scanned it and gave you back the image on a disk. ◦ Still common. ◦ The prices and sizes of these scanners have dropped considerably. ◦ It still takes a trained operator to get the best quality scans. ◦ Drum scans have been relegated to extremely high-end work

Scanning Printed Artwork:

In a perfect world, you would always have the original photograph, artwork, or negative of the art you want to scan. ◦ We don't live in a perfect world, and people do need to scan images that have already been printed. ‣ Problem is that when you scan printed artwork, you pick up the original line screen. ◦ You probably won't see any problems in this kind of scan when you view it on the monitor, but you'll see problems when the image is printed. ◦ Original line screen combines with the line screen for the new scan and causes a moire pattern. ‣ There are steps you can take to avoid moire patterns when scanning printed artwork, but they're not always affective

Hand-Held Scanners:

Least expensive scanners are those small ones you hold in your hand and drag across an image. ◦ Supposed to be easier ◦ Not recommended for printing a high-quality image

Flatbed Scanners:

Most common type of desktop scanners and most closely resemble the top of an office copy machine. ◦ Can handle reflective art and some have adapters for transparent art. ◦ Can even place small objects such as coins, keys, pencils, hands, etc. On top of the flatbed scanner. ‣ Makes scanning a quick substitute for photography. ◦ It's possible to get high-end results with a flatbed scanner that costs just under a hundred dollars

Contrast and Colour Controls:

Most scanners have some sort of controls for adjusting the colours and contrast of the image. ◦ As a general rule, adjusting the controls as you scan is better than using other software to adjust the image later. ◦ You may find that your image editing software has better controls over colour and contrast than your scanner. ◦ Experiment with your scanner and see what works best for you

Setting the Resolution:

Most scanners let you set the resolution of the scan in one of two ways; by choosing the actual resolution for the image, or by choosing the output media such as newspaper or magazine. ◦ If you are planning to print on a commercial press, call them and ask them; ‣ What is the resolution you recommend for my project? ‣ What resolution should I use?

Descreening Printed Art:

Most scanning software programs have a control that is supposed to descreen printed artwork. ◦ This feature will blur or merge the dot pattern into a solid set of pixels — in theory! ‣ Descreening is a hit-or-miss affair that avoid a moire pattern. ‣ Problems; it softens and distorts artwork so that it's obvious it's not an ordinary image. ◦ Descreening controls are usually listed as the linescreen you are trying to blur; 150 LPI, 133 LPI, 120 LPI, and so on. ‣ The original screen amount you choose, the higher amount of blur. ‣ Descreening doesn't apply to just the dots, but to the entire image; this softens the solid areas of the image as well. ◦ If your scanning software doesn't have the descreening feature, you can try blurring and sharpening the image yourself. ‣ Inkjet printer - will reduce some of the screening in the image by the very nature of the printing process. • Bottom line: Unless you have very expensive equipment, and years of experience, don't expect high-end results when scanning previously printed images

Scanning Printed Colour Art:

Previously printed art in colour is probably the hardest type of image to scan and have it look good. ◦ If you plan to reprint the scanned image in colour, you need to scan as RGB colour and not line art. ◦ Convert to CMYK (unless you plan to print as RGB to an inkjet printer) and then make separations. ◦ Must also apply some sort of "descreening" to avoid a moire pattern. ‣ Descreening is not a perfect solution.

Scanners use RGB:

Scanners capture the colour information as RGB (red, green, blue) ◦ This makes perfect sense because the point of a scanner is to put the image into the computer, which displays colour as RGB. ◦ If you plan to output a graphic in CMYK, work on your file in RGB, then convert it to CMYK just before you place it onto a page layout page for final output

OCR Software:

Scanners make pictures of images; they do not read text. If you scan a page of text, like from a book or a typed letter, you'll get a picture of the text — you won't be able to edit, change the typeface, or search the text. ◦ Special software called Optical Character Recognition (OCR) that is often included with scanners, or you can but it separately to use with your existing scanner. ‣ It recognizes the shapes of letter and creates an editable text file from the page on the scanner. ◦ Useful for converting large amounts of printed information into editable text. ◦ Can take some time and effort to get all of the text translated correctly. ‣ For a single sheet of text, a fast typist may be quicker and more accurate than scanning. And using OCR software; for a large body of work that needs to be digitized, OCR is an incredible solution

Sharpening:

Some scanning software lets you apply what's called sharpening (also called us harp masking) as you scan. ◦ Sharpening compensates for the slight blurring or softness in a scanned image by looking for any differences between the colours of the image. ◦ Then accentuates these difference, which makes the edges in the image more defined. ◦ Prefer to do my sharpening in Photoshop after I scan an image. ◦ Limit your sharpening to no more than 60-80 percent of the total amount possible

Colour Mode:

Some scanning software offers two ways to set the colour mode; One uses the digital terminology such as line art, grayscale, RGB, etc. ◦ The other uses common descriptions of the type of artwork. ‣ You still have to know what the terminology means

Slide Scanners:

Specially made scanner for transparent are, such as slides. ◦ Use extremely high resolutions to provide enough detail so a 1-inch image (the slide) can be enlarged to fill a full page without the pixels becoming obvious. ◦ Fewer photographers take pictures with film cameras, the slide scanner has become an endangered species with only rare sightings in graphic design firms

Bit-Depth:

The bit-depth of a scanner refers to how much colour information the scanner can capture. ‣ 1-bit scanner captures only line art images. ‣ 8-bit scanner captures grayscale. ‣ 24-bit scanner captures RGB images. ◦ Most office desktop scanners are 30-bit, while the higher quality graphic scanners are 36-bit. ‣ Means they can capture extra information about the colours of an image. ‣ Added bit-depth about the image provides more information to use during the colour and tonal correction of an image

Scanner Resolution:

The optical resolution of a scanner refers to how much detail the scanner can capture ◦ Optical resolutionis expressed as two numbers, such as 600 x 1200 PPI. ◦ First number, 600, is the number of pixels per inch of information the scanner captures in the horizontal direction. ‣ The higher the number of pixels per inch, the more detail the scanner can capture. ◦ The second number, 1200, refers to the number of steps the scanner head moves along the vertical direction. The actual resolution of the image is only the number of pixels per inch, not the number of steps. ◦ The resolution of a scanner expressed ass the interpolated or enhanced resolution. ‣ Interpolated resolution is much higher than the optical resolution. ◦ A scanner with an optical resolution of 600 x1200 PPI might have an interpolated resolution of 9600. ◦ The scanner software is able to interpolate (kind of fake) the true resolution of the image into a higher number. ‣ Interpolation doesn't actually increase the detail in an image — it just means the image can be enlarged without any obvious pixelation

Original Images:

The sorts of things you can put through the scanning process can be divided into two catergories; reflective art and transparent art. ◦ Reflective art or images are physical objects such as photographs, canvasses, paintings, or objects. ◦ Transparent art or images include film, slides, acetate, etc. The scanner captures the light as it passes through the original image

Preparing to Scan:

Using a flatbed scanner, some general principles you should follow to make sure you get the best quality scan. ◦ Clean the glass. ‣ Make sure you keep the glass of the scanner as clean as possible. ‣ Watch out for small defects —dust, scratched, and fingerprints all affect the final quality of the scan . ◦ Take care of the art. ‣ Handle the art carefully to make sure it doesn't pick up any fingerprints, dust, scratches, etc. ◦ Use glossy photos. ‣ Photos on glossy paper make better scans than photos on matte surfaces. ◦ Straighten the image. ‣ Make sure the image is as straight as possible. ‣ You can use the edge of the glass to align the photograph, but because the optical quality of the glass is better in the center, you may want to place the art in the center of the scanner. ‣ Don't rely on rotating the image electronically because it forces the pixels in the image to resample, which causes a loss of detail. • It is much better to scan perfectly straight, if at all possible. ◦ Keep the image on the glass. ‣ Put the top of the scanner down on top of the art to apply uniform pressure on the image. ‣ This. Keeps all the portions of the image in focus. ◦ Avoid vibrations and motion. ‣ Avoid jostling the machine while the scan is in progress to keep the light source constant as it passes along the image

Scanner Software:

Very few controls on the scanner itself. ◦ All the controls for the scanner are in the software. ◦ Each scanner company has its own brand of software

A Legal Note About Scanning:

You can't just grab any magazine or book and scan whatever is inside and print it in your own projects. ◦ Someone somewhere owns the rights to the image. ◦ Most magazines copyright their entire issue. ◦ The photographs may be owned by the photographer. ◦ Advertisements are copyrighted by the companies that bought the ads. ◦ Websites are all copyrighted. If you cant get permission to use an image, don't use it!!

Sheet-Fed Scanners:

You insert (feed) a paper image into the scanner that resembles the top of a fax machine. ◦ All sorts of paper sizes. ◦ Save the scanned images as a PDF file. ◦ Sheet-fed scanners can handle hundreds of pages of material at a time. ◦ Great for converting tons of paper into electric documents. ◦ I wouldn't use a sheet-fed scanner to capture an image for a professional publication. ◦ The paper moves over the scanner head (instead of the scanner moving over the paper) means there can be variation along the line of the scan

Scaling during Scanning:

You should not resize an image unless you understand how it will change the resolution. ◦ It's perfectly safe to resize (scale) an image when you scan it

A scanner allows you to capture objects outside the computer and put them inside the computer...

◦ No matter how much it costs, a scanner doesn't scan objects as automatically as a point-and-shoot camera; if you don't set the right settings on the scanner, you wont get good results. ◦ They used them to scan prints and negatives of photographs to use in their designs. ◦ The need for scanners has dropped dramatically with the increased availability and lower prices of professional digital cameras