On Graphics: Getting images, scanning, file formats

GETTING IMAGES

Scanning, PhotoCD, Digital Cameras

SCANNING
slides, flat artwork and objects, photographs

The quality of the scan depends on quality of scanner.

Professional: Drum scanner, CCD Scanner (CMYK)

Retail: Flatbed (RGB)

Modes: Grayscale, Black and White Line Art, Color

Resolution:

Scan resolution is measured in pixels per inch (ppi)

Screen resolution is measured in dots per inch (dpi)

Inkjet printers: use 200 ppi or greater.

How many bits per channel do I want?

High end: 16

Low end: 8

Note: some printers will not print more than 8 bits/channel

What is a bit?

Donπt ask.

Bit:

Short for binary digit, the smallest unit of information on a machine. A single bit can hold only one of two values: 0 or 1. More meaningful information is obtained by combining consecutive bits into larger units. For example, a byte is composed of 8 consecutive bits.

FILE FORMATS

PSD, BMP, JPEG, PCX, PICT, PIXAR, TIFF, TARGA, GIF, PNG

http://www.quepublishing.com/articles/article.asp?p=169557&seqNum=3

Every file format that Photoshop can create or import has specific capabilities and purposes, note some below:

PSD
Photoshop's native file format supports all the program's capabilities.

Large Document Format (.psb)

New in Photoshop CS is the capability of saving truly huge images. In earlier versions of Photoshop, the maximum image size was 30,000 pixels by 30,000 pixels. The new PSB file format can handle images as large as 300,000x300,000 pixels. Note: remember that Photoshop's Large Document Format (PSB) is not available until you enable the feature in the File Handling pane of Photoshop's Preferences dialog box.

CompuServe GIF

GIF is a common Web file format, suitable for illustrations and other images with large areas of solid color and no or few gradients or blends. Many logos and cartoons, as well as Web navigation items, such as banners and buttons, are appropriate for GIF. This file format is not appropriate for most photographs and other continuous-tone images because it can record a maximum of only 256 distinct colors.

Photoshop EPS

PostScript is a page description language developed by Adobe, and it was at the heart of the desktop publishing revolution of the 1990s. An Encapsulated PostScript (EPS) file can contain any combination of text, graphics, and images and is designed to be included (encapsulated) in a PostScript document.

One of the greatest advantages of EPS as a file format is the capability of including both raster and vector data and artwork.

JPEG

Joint Photographic Experts Group (JPEG) is technically a file compression algorithm rather than a file format. The actual file format is JFIF (JPEG File Interchange Format), although JPEG is more commonly used. JPEG supports Grayscale, RGB, and CMYK color modes and can be used with files more than four times as large as Photoshop's 30,000x30,000 pixel maximum. JPEG does not support transparency, alpha channels, spot colors, and layers. Paths can be saved with a JPEG file, including clipping paths (although most programs can't use the clipping path, with the notable exception of InDesign). Type is rasterized when a file is saved as JPEG.

JPEG is commonly used on the Web for photographs and other continuous-tone images in which one color blends seamlessly into another.

JPEG 2000 (.jpf)

JPEG 2000, an improved variation of the JPEG file format, is now supported in Photoshop. Although this format is used for both print and the Web, most Web browsers require a plug-in to display JPEG 2000 images.

Photoshop PDF

Adobe's Portable Document Format (PDF) is a cross-platform format that can be opened and viewed in the free Acrobat Reader, available for most computer operating systems. PDF is, at heart, a PostScript file format. Photoshop breaks PDF into two categories: Photoshop PDF and Generic PDF. Both can be opened, but only the former can be created.

Raw

In Photoshop, it's necessary to differentiate between Raw files saved from the program (Photoshop Raw) and digital camera files being opened in the program (Camera Raw). Many high-end cameras use proprietary versions of the Raw format. Previous releases of Photoshop could not natively open such files. The various camera manufacturers had their own software to open and process the files, from which you could save a TIFF file to open in Photoshop. In early 2003, Adobe released a Photoshop 7 plug-in called Camera Raw for use with the top cameras from Canon, Nikon, Minolta, Olympus, and FujiFilm. That plug-in has been incorporated into Photoshop CS and has some additional capabilities.

Photoshop Raw

The Photoshop Raw file format records pixel color and very little else. Each pixel is described in binary format by color. Because the file doesn't record such basic information as file dimensions and color mode, coordination and communication are important. If incorrect data is entered into the Raw Options dialog box when an image is opened, an unrecognizable mess is likely to result

Camera RAW

When you select and open an image from a high-end digital camera, Photoshop will, if necessary, launch the Camera Raw plug-in. (Some Raw files can be opened directly in Photoshop.) The Camera Raw plug-in offers very powerful image-adjustment capabilities. Global color and tonal adjustments, sharpening, noise and moirÈ reduction, and compensation for color fringing caused by chromatic aberration are some of the features of Camera Raw.

TIFF (.tif)

Tagged Image File Format (TIFF) and EPS are the two most widely accepted image formats for commercial printing. TIFF files can be produced directly by most desktop scanners and many digital cameras. The format supports CMYK, RGB, Lab, Indexed Color, Grayscale, and Bitmap color modes. In Bitmap mode, alpha channels are not supported, but they are available in all other color modes. Spot channels are supported, and clipping paths can also be saved with TIFF images to denote

Photoshop DCS

Desktop Color Separations (DCS) is a version of EPS developed by Quark. (The file that's produced has the .eps extension.) The original DCS file format is now referred to as DCS 1.0, whereas an updated, more flexible version is called DCS 2.0.