120 ART Digital Foundations One PROF. Jones F2008 _________________________________________________________________________________________________
1. PIXEL & RESOLUTION
WHAT IS A PIXEL? Pixels are small square picture elements that contain color, grayscale, or black and white information that is shown on the monitor or sampled while scanning, or can be even referenced to the dot on the print. Pixels vary in size depending on the resolution. The higher the resolution number (comprised of more pixels), there is more detail in an image (clarity and higher quality of image) whereas the lower the resolution number (comprised of less pixels), there is less detail in an image (less clear, pixelated, and poor quality of image). WHAT IS RESOLUTION? Resolution refers to the number of pixels per unit of measure in the digital image of the monitor, scanned image of the scanner, or printed image from a printer. Resolution is commonly expressed as pixels per inch (ppi), samples per inch (spi), and dots per inch (dpi). Commonly, PPI is used for referencing pixels per inch on monitors and is the measurement of output resolution on monitor screen. SPI is used for referencing samples per inch in scanning and is the measurement of input resolution of sampling (scanning) an image with a scanner or image setter. DPI is used for referencing dots per inch to be printed and is the measurement of output resolution on a laser printer or image setter. RESOLUTION AND SCANNING: Pixels that are sampled by scanning vary in size depending on the number of resolution. At 150 spi, the scanner takes a sampling of the image every 150th of an inch; at 72, samplings are taken every 72nd of an inch, and etc. The higher the scanning resolution, the greater the amount of detail that can be captured. Photoshop allows you to change these settings.
Jones/Saturday, September 13, 2008 1/ 13
The image to the left, (say hello to baby Coco!) is an RGB image @72ppi. I created this image with a digital camera, (the original hi-resolution images vital signs are easily called up in Photoshop, by calling up Image Size in the menu bar). You can see below that the original image is 3,872 pixels wide by 2592 pixels high. Multiplying the height and width of a digital image gives you the total pixels the image has, in this case, 10,036,224. Ten million, thirty-six thousand, two-hundred and twenty four, which is the equivalent of 10.036 MEGAPIXELS, the term commonly used to describe the capture capacity a digital camera has. The image you are viewing in this document, however does not need that level of resolution. It has been reduced or resampled to a 72ppi image, which is all thats necessary to view it on screen. Remember that using the correct resolution is very important in design. Any images that you use for the screen within web pages, dvd-menus, pdf portfolios, kiosks, etc. only need 72ppi. Any more makes those images load sluggishly and is the mark of an amateur. Your images need to load swiftly and look good. This is called image optimization.
Jones/Saturday, September 13, 2008 2/ 13
<<<
ONE INCH
>>>
the square in between each blue line=one pixel.
The image to the left is an enlargement of the 72ppi image at 400%. Ive gridded out the image pixel by pixel so you can see the amount of total pixels per inch. Below is an enlargement at 1450%. Here, you can see, even more clearly, each individual pixel. Each pixel represents a particular point on the image which has a distinct color value.
In digital imaging, you control how much resolution you want to put in an image considering the limitations of your capturing device (scanner, camera, etc.)
Jones/Saturday, September 13, 2008
3/ 13
TOO HIGH RESOLUTION IS COUNTERPRODUCTIVE: On the other hand, scanning or printing with a too high of a resolution number will be counterproductive, the le size of the image will be unnecessarily large causing delayed and longer processing time for scanning and printing. When the resolution is too high, there is no gain in the actual quality of the image that can be seen with the naked eye. SCANNING AND PRINTING RESOLUTION MAXIMUM: Regardless of output resolution, 600 spi is a good maximum for scanning an image. Something like scanning or printing at 1200 spi is counterproductive since the difference of quality will be hard to see with the naked eye. A rule of thumb for printing is that the image resolution of the le should be twice the amount of the printing resolution. PRINTING RESOLUTIONS ARE BASED ON LPI: To make matters even more confusing, Printers (both offset and desktop) use a term lines per inch to describe the effective resolution of the print. Remember that the printing process re-interprets your images and lays the respective image/ graphics in a pattern on the paper. The effective resolution of this print is dependant upon the screen or style of patterning the image to be printed. Resolution in printing industry is expressed in lines per inch (lpi). Resolution in the digital world is expressed in dots per inch (dpi). As a rule of thumb, dpi should be twice the desired lpi, at 100% size. READ THIS LINK BELOW for a more complete discussion concerning DPI, PPI and LPI. http://www.adobeforums.com/webx/.3bb51427
Jones/Saturday, September 13, 2008 4/ 13
RESOLUTION FOR Mac Lab:
Printing your work through printers in the Mac Lab (which range from 120-150 lpi), youll need the digital image to be between 240-300dpi. The largest print size available in the lab is 12 x 18, so remember that if you have a small item to scan and your intention is to make it into a larger print, you will need to give it more resolution. If you have a 3 x 5 drawing and you want it to be 6 x 10, you would then need to scan it in at 600 spi (samples per inch). Printing anything at 72 dpi will be a poor quality. It is recommended to never print at 72 dpi. 150 dpi should be the minimum for printing, and 200-300 dpi or higher is recommended depending on the scale of the print size.
If your image will be viewed on-screen/web, etc. the resolution should be 72 ppi, the standard resolution of monitors since images are to be seen only by computer monitors. In the past, 96 ppi was used for creating image for the web on PC but nowadays most people use 72 ppi cross-platform (PC and MAC). A standard American NTSC video system outputs images at the size of 640 x 480 (4:3 ratio) pixels at 72 ppi and this is the standard for most computer monitors. Although one would never print at 72 dpi, 72 ppi is the correct resolution to work with on any screen-based images (for
Jones/Saturday, September 13, 2008 5/ 13
web, video, CD-ROM titles). For making webpages, it is important to make le sizes (in bytes) as small as possible while maintaining good quality of the image since one would want to lessen the downloading time of the image. This is called image optimization.
CHICO Xerox Phaser 860 Letter + Legal Size Ink Stick 600 x 600 dpi or 600 x 1200dpi (hi res mode) Duplexes: Can print on both sides of paper HARPO Xante Accel-A-Writer 3N Letter, Legal + Tabloid Size Min. print size 3.94" x 5.83" (100 mm x 148 mm) Max. 13.00" x 18.50" (330 mm x 470 mm). Black Toner only 600 x 600 dpi or 1200 x 1200 dpi (hi res mode) Factory Default LPI=85LPI Can be set up to 210LPI Download Manual PDF
GROUCHO Xerox Phaser 790DP Letter, Legal Size + Tabloid Size Minimum: 3.5 x 5.5 (90 in. x 139.7 mm) Maximum: 13 x 18 in. (330.2 x 457.2 mm) Maximum image size: 12.6 x 17.2 in. (320 x 437 mm) Color Toner (Cyan, Magenta, Yellow, Black) 600 x 600 dpi Duplexes: Can print on both sides of paper
ZEPPO Xerox Phaser 7750DN Letter, Legal Size + Tabloid Size Can print up to 48 long through manual pass tray. Color Toner (Cyan, Magenta, Yellow, Black) 1200 x 1200 dpi Duplexes: Can print on both sides of paper
PRINTERS IN THE MAC LAB
Jones/Saturday, September 13, 2008 6/ 13
2. BIT DEPTH AND COLOR MODES
WHAT IS BIT DEPTH AND COLOR MODES? Bits are the basic elements of digital data. A single bit is either on or off, usually expressed as 1 or 0 so that there are only two variations. Each pixel of an image has a "depth" of one to 32 bits and each image can be set to different color modes that represent different forms of variations to bit depth and color palette choices. 1-bit depth images contain 2 color variations (0,1), black and white, making it DUOTONE COLOR MODE. 2-bit depth images contain 4 color variations (00, 01, 10, 11), black and white and two gray tones in between, making it QUADTONE COLOR MODE. 8-bit depth images contain 256 color variations (numbered as 0-255), making it GRAYSCALE or INDEX COLOR MODE (color mode for Web). 24-bit depth images contain 3 channels of 8-bit depth color variations (0-255 x 3 channels) which is 256 color variation of RED, 256 color variation of BLUE, and 256 color variation of GREEN, making it RGB COLOR MODE = the color mode for light. 32-bit depth images contain 4 channels of 8-bit depth color variations (0-255 x 4 channels) which is 256 color variation of CYAN, 256 color variation of MAGENTA, 256 color variation of YELLOW, and 256 color variation of BLACK, making it CMYK COLOR MODE the color mode for printing. Another form of 32-bit depth is known as RGB & ALPHA CHANNEL COLOR MODE, a grayscale channel mode with RGB used for quickmask and other techniques in photoshop.
Jones/Saturday, September 13, 2008 7/ 13
Different color modes can be changed in Photoshop by going under the menu Image or one can set the color mode when making a new le.
DIFFERENCE BETWEEN RGB & CMYK:
RGB is made of primary colors of "light": Red, Green, Blue. The human eye responds to stimuli from varying RGB wavelengths and renders the appropriate signals to the brain so that we perceive such colors as cherry, mauve, and taupe. RGB is also the color mode for light thats emitted from a source such as a video monitor. Most scanners also use an RGB color model for recording digital image data. RGB color is called additive because colors throughout the spectrum are created by adding varying intensities of red, green, and blue light to black (no light). These intensities range from 0 to 255 (256 color variation in 8-bit depth color mode) and the combination of 3 channels values equates a variation of 16,777,216 colors, known as "millions of colors" (especially in monitor display settings). The additive of all colors makes WHITE and the absence of all colors makes BLACK in RGB color system. CMYK is made of secondary colors of RGB and are opposites to RGB: Cyan, Magenta, Yellow, and Black. When RGB light strikes an object, the amount of CMY in the objects pigmentation affects how much light is reected back. It is the reected light that we see. Cyan absorbs red light, magenta absorbs green light, and yellow absorbs blue light. The degree of absorption depends on the amount of pigment or, in printing terms, the amount of CMY ink. This is why CMYK is considered subtractive; the colors displayed by CMYK are the result of subtracting varying amounts of red, green, and
Jones/Saturday, September 13, 2008 8/ 13
blue light. Opposite to the way RGB works, the additive of all makes BLACK and the absence of all colors makes WHITE in CMY color system. This is why in printing the color white is the space of NO colors. RGB is the default color mode for pixel-based software applications such as Photoshop, Paint, and etc., that is known as BITMAP GRAPHICS. CMYK is the default color mode for line-based software applications such as Illustrator, Corel Draw, and etc., that is known as VECTOR GRAPHICS or POSTSCRIPT GRAPHICS. At times, CMYK can be set as the color mode for Photoshop and RGB for Illustrator. RGB however, is mostly used for Photoshop since it is the colormode of "light" and Photoshop is an application that does digital darkroo...