Digital Printing Technology

Pixels and crystals are now on equal footing as affordable digital cameras allow us to produce photographic files equal or superior to the conventional film images of the twentieth century.  As digital cameras increase their capacity to store more pixels so must the printers that are used to output these images.  Every step forward in digital camera resolution must be matched by advancements in printing technology.

Conventional color photographic printing by means of a chemical darkroom produces continuous tone analog images that are made up of random dots of color dye that formed around microscopic pieces of silver.  Digital prints can be made on a variety of papers with wax or pigmented inks, with laser light on conventional photographic papers, pigments that are sublimated into a gas and blended to form images or they can be etched into a metal plate and printed with lithographers inks.  What most of these methods have in common is that the image is first converted by a computer into a series of dots.  The limiting and differentiating factor in all digital means of printing images is the way these dots are mechanically placed on a surface and the size of the smallest dot the device is able to produce.  There are many printer choices, from low to high resolution, capable of simulating continuous tone photographs.  Some can make digital prints that are indistinguishable from chemically made prints others can produce images with color or smoothness not possible with traditional photographic processes.  Figure 8.1 shows the differences in how a continuous tone image is formed from film, digitally on a screen, and by ink.

 

Forming a Continuous Tone Image from Film (grain), Digital (pixels), and ink (halftone). 

 

Displaying the Image

 

Screen Resolution (PPI) & Dot Pitch

Screen resolution, pixels per inch (ppi), and print resolution, dots per inch (dpi), are two different measurements and are often used interchangeably.  They must be clearly understood to properly scan, scale (image size), and to prepare images for the web or to print.  Screen resolution (ppi) is the maximum number of pixels per inch a monitor can display at any one time.  PPI is determined by the manufacturer and cannot be changed.  It is usually between 72 and 90ppi, but varies slightly from monitor to monitor.  The dot pitch (Figure 8.2) rating of any screen only determines the quality of the display monitor.  PPI is measured in millimeters (mm) and theoretically the lower the number the sharper the image.  Although cathode ray tube (CRT) and liquid crystal display (LCD) screens are mechanically different, the dot pitch rating is still the same and ultimately only slightly affects image size on a screen, but NOT print size.

 

 

Dot Pitch

 

Print Resolution (DPI)

Print resolution (dpi) or dots per square inch refers to the number of dots a printer can apply within one physical inch on paper.  Dpi is variable and many inexpensive printers average 1200 dots per square inch.  Image quality is increased when more and smaller dots are contained within the same inch of physical space on the paper or material.  The more dots per square inch, the more continuous tone and photographic the image will look.  The most common color printer for photographs is an ink-jet printer that sprays tiny dots of color to create an image from a digital file.

Since screen resolution (ppi) and printer resolution (dpi) are two different measurements they can become confusing when scanning, scaling or resizing your digital photograph for printing.  Figure 8.4 demonstrates what happens to an image that is scanned at a dpi higher than 72 and viewed on the display at 100 percent. The screen image will appear larger than one anticipated, requiring re-sizing of the screen image.

 

 

This photograph was scanned at 72 dpi with a print dimension of 3 - 5/8 x 2 - 7/8 inches.  Notice the picture and rulers closely approximate 1 inch of actual length and width when viewed at 100 percent in the photo-imaging software.  With this 72 dpi scan the screen size and print size will be similar because the screen dot pitch (ppi) closely resembles the true physical inch when output to paper.  This would be considered a 1:1 ratio in regards to scale when viewing at 100 percent on screen when compared to the print size.

 

Here the same photograph was re-scanned at 300 dpi at the same dimensions, 3 - 5/8 x 2 - 7/8 inches.  Notice that the screen rulers now exceed 1 inch of actual length and width when viewed at 100 percent. Now it requires 300 screen pixels (ppi) to represent the 300 dots (dpi) as one inch. This would be considered a 4:1 ratio in regards to the imageÕs scale on screen when compared to the actual print size.  The image will still print 3 - 5/8 x 2 - 7/8 inches, but now at higher resolution.

The Image Window

To help keep track of all the variables in a digital file, software programs display many key pieces of information about the image.  Figure 8.5 identifies this data that surrounds the working image and describes their meaning.

 

1. Scale: Since a monitor can only display about 72 ppi your image program scales the image to show the difference between the screen display and the bit depth (resolution in ppi) of the actual image.  Figure 8.5 above shows an image with a bit depth of 300ppi image.  In this case the software has scaled the display of the image to only show 16.7 percent of the actual pixels contained in the image.

2. Image Mode:  Imaging programs allow one to work in a variety of color modes including RGB, CMYK, Grayscale, Bitmapped, Duotone, or LAB.  Some filters and operations can only be performed in RGB mode.

3. File Size:  This area shows the size of the file when it contains only one working layer.

4. File Size (with layers): Layers are transparent surfaces that can be individually placed on top of the original image, adding to the file size.  You can move, scale, draw, edit, and paste on to any layer without disturbing the other layers or the original image.  Adding layers while working allows you to work separately on the various parts of your image, which helps to organize and manage the workflow.  Flattening an image converts all layers back into one, reducing the file size.  Images that are sent to high quality printers often have to be flattened before printing.

5. File Name: Most imaging software will display the name of the file somewhere along the top of the image window.

6. Extension: Extensions describe the file format to the computerÕs operating system.  PCÕs and web browsers require the three-letter file extension be included in a fileÕs name, such as .doc or .jpg, in order for it to be opened or displayed.

7. Ruler:  Most imaging software includes an option for displaying a ruler along side an image.  The user can usually define the particular units a ruler uses.

Sizing a Digital File

As previously discussed, file size in megabytes (MB), screen resolution (PPI), and print resolution (DPI), are three different measurements that need to be understood to be able to properly scale, scan, and prepare images for printing or the Web.  Although closely related MB, PPI and DPI are not a true measure of the actual image size when outputted to paper or viewed on the screen.

            The size and quality of the final print is first determined by how many pixels were originally exposed by the camera or scanner. The original exposure or scan is absolutely crucial towards determining levels of quality for the final print. Digital cameras capture images based on the common settings of High, Fine, Normal, and Basic.  Low-resolution settings, such as Basic for the camera or 72 dpi for scanning, will produce a file usually of under one megabyte that is only suitable for images appearing on the computer screen or on a Web page.

Once the file is captured/scanned, changing the resolution will affect the file in different ways, depending on how the change is made.  For example, a digital camera using the Fine setting might produce an image file of 1600 x 1200 pixels.  Depending on the camera and software, this image may import into your software program at a default resolution of 72 dpi and pixels dimensions of 1600 x 1200, which will make the print size 22.222 x 16.667 inches at 72 dpi

The print size is very large at 72 dpi and when outputted to paper would produce a soft-focus or pixilated image with only 72 dots per square inch.  Changing the resolution to 300 dpi would more closely match conventional photographic quality.  In this image, changing the default 72 dpi up to 300 dpi, for seemingly better visual acuity, will result in adding 31 million more pixels to the image because width and height dimensions were not scaled down proportionately!  The computer has to resample, also known as interpolation (see next section), by placing extra pixels in the image. To do this the computer looks at adjacent pixels and places new pixels between them that are based on an average of the original two, which creates a look called pixelization.

To change the resolution (dpi) to an existing file, simply change the number in the resolution box to 300 dpi (see figure 8.7).  This change will not affect the print size or improve the print quality because resampling/interpolation will occur.  Only the file size (5.59 MB to 95.4 MB) will change with no increase in detail.  The original un-interpolation 72 dpi image file and itÕs new 300 dpi interpolated counterpart will print very similarly.  There is no gain in the detail of the interpolated image file.  However, re-shooting at a higher pixel dimension is necessary to maintain detail at larger print sizes.

 

Interpolation or Resampling

Changing pixel dimensions forces the software to interpolate the changes.  Interpolating is a set of mathematical logarithms automatically applied when the original pixel dimensions are changed for resizing.  Interpolation cannot add or subtract detail, it only randomly adds or subtracts pixels making a Òbest effortÓ when resizing the original pixel dimensions.  There are many interpolating logarithms that perform slightly different mathematical computations, but the end result is still degradation of the original image file that will affect image quality as the computer is literally making up the information.

The three most common modes of resampling, which appear when the Resample Image box is checked, are Bicubic, Nearest Neighbor, and Bilinear. Always use Bicubic interpolation because it gives the smoothest results.  Although Bicubic takes longer to compute the speed of todayÕs computers make it negligible. Nearest Neighbor is the fastest interpolation method producing the most jagged results and Bilinear splits the difference between the two.

 

Equivalent Image Size

When learning to control camera exposure one comes to understand the concept of equivalent exposure.  This model states that when one changes from a slow shutter speed (1/60 of a second at f/11) to a faster shutter speed, one must compensate by using a larger aperture (1/125 of a second at f/8) to maintain the same exposure.  The reverse was also true.  A similar equivalent concept holds true for changing the size of digital images.  Figure 8.8 shows two image size windows for the same image.  By linking the document sizes by checking the Constrain Proportions box and the Resample Image box one can change the resolution of an image without the computer adding or subtracting pixels to an image, thereby maintaining the original image quality (See Figure 8.8.).

 

Links Between Document Size & Resolution

A simple mouse click in the check box next to Resample Image turns linking on and off.

By constraining the proportions of the height, width, and resolution we can alter the value of one variable and the program automatically compensates by increasing or reducing the other two.  Before and After are equivalent because when we add to the resolution the software program automatically subtracts from the height and width to maintain the same file size.  Notice in the Pixel Dimensions box the number of pixels referencing height and width has not changed and neither has file size.

 

The Real Size of a Digital Negative

A good way to understand the relationship between picture size, pixel dimensions, and dpi is to think of pixel dimensions as representing the real size of the Òdigital negativeÓ.  The digital negative is the total number of pixels from which there are a limited number of un-interpolated print dimensions available to produce un-pixilated images regardless of dpi.  Print size or print resolution (dpi) is not as significant as minimizing the effects of interpolation. A 2.1 megapixel digital camera or a 300 dpi scan at 4 by 5 inches are both capable of producing a digital negative of 1,920,000 pixels.  Figure 8.9 illustrates the relationship between dpi, interpolation, and print size. Note: as the print resolution increases from 72 dpi to 1200 dpi the print size is proportionately decreased to maintain the original number of pixels to the digital negative. Also notice two exceptions, the interpolated files will print less than optimal because pixels were randomly added or subtracted to compensate for print dimensions that did not remain proportional to the original 1,920,000    pixels. Both these interpolated files will show some pixelization but the file with less than the total original pixels will show less pixelization.

 

Figure 8.9 The Digital Negative: Avoid Interpolation

 

Table 8.1 shows how to make sure the original pixel dimensions (ppi) correlate exactly to the final output size (dpi) in regards to length and width.  The pixel dimensions should always remain constant as the digital negative is enlarged or reduced.  For example, when using a 2-megapixel camera on the Fine setting an image file of 1600 (W) x 1200 (L) pixels equaling 1,920,000 total pixels is made.  These 1,920,000 pixels now represent the physical size of the image and becomes the limiting factor when resizing the image for optimum results.  Since 300 dpi is considered the acceptable printing resolution to create digital pictures similar to film photographs, one divides 300 into the original pixel dimensions to determine the optimum output print dimensions (Table 8.1).

Table 8.1 Calculating Optimum Print Dimensions

 

Achieving Photographic Quality

 

Ink-jet Printers: Dpi to Dots to More Dots

 

Photographic quality ink jet printers are needed to produce prints that have the look of continuous tone.  Their print head design allows them to spray minute amounts of inks onto the receiver material at resolutions of 1440 x 720 dpi and higher.  They can also deliver subtle detail with more accurate and saturated colors and print on a wider variety of materials than their less expensive office counterparts.  These quality printers use more permanent inks and include additional colors greatly increasing the range of colors (color gamut) beyond traditional color photography.

         All inkjet printers use different amounts and methods of applying inks to create photo-realistic images.  General-purpose quality inkjet printers use four inks, cyan, magenta, yellow and black while higher-end photo quality inkjet printers can easily exceed four colors by adding orange, green and lighter versions of cyan, magenta and gray.  Creating photo quality photographs is not only dependent upon how many droplets fit with in an inch (dpi) of space, but also on the size and pattern of the ink droplets.  When a photo quality inkjet printer creates an image from a 300 dpi file it is not just creating one droplet of ink for each pixel (ppi) or dot (dpi), but rather it places four or more droplets of ink for each particular dot.  Color inkjet printers may have as many as 96 nozzles per color for applying droplets, which is a total of 672 nozzles to apply varying degrees of color and value.

Inkjet printers are rather complicated printing devices that must control all those nozzles accurately to create droplets of ink that can convince the eye of continuous tone.  Better inkjet printers are capable of delivering excellent photo quality between the range of 150 and 360 dpi.  Although these printers are capable of resolutions up to 2880 dpi, it is generally not worth the printing time and storage space to produce image files greater than the visual acuity of the human eye.

 

Paper: Un-coated and Coated

Un-coated (porous) printing papers are the most readily available papers and are best identified as the inexpensive xerographic, ink-jet or laser-jet papers used primarily for text. Structurally these papers are raw cellulose wood fibers bleached and processed into the standard letter and legal sized formats. These papers have less uniformity when considering brightness, surface texture, absorbency and pH levels. These un-coated papers absorb more ink allowing them to print and dry faster to the touch.  The downside of these materials is that they are more susceptible to fading due to environmental factors and exposure to light. Coated papers (micro-porous) have special coatings that either modify or completely cover the cellulose fiber making the paper achieve superior print results and archrival qualities. These papers are designed to resist fading although drying times can be somewhat longer. Coated papers come in a variety of traditional photographic surfaces including high gloss, semi gloss, flat matt, luster and also in many canvas-like textured surfaces. Non-porous materials are polymer or vinyl based printing materials for banners or decals. The smart advice is to check the kind of coating or surface that exists with the printing material to be used and choose the appropriate type of ink, making sure the existing printer can handle the combination.

 

Inks: Water-Soluble and Pigment Based

There are also two groups of inks: water-soluble dye-based and pigment-based.  Inexpensive ink jet printers use water soluble inks and should only be used when permanence is not a concern, such as for color proofing and short-term use. Photo quality ink jet printers use pigment-based inks that contain small waterproof color flecks that makes the inks more fade resistant and richer in color.

 

Print Permanence

There has not been enough independent empirical testing to accurately predict the permanence of ink-jet prints plus the equipment and materials have been in flux.  To maximize longevity use coated (micro-porous) papers and the best quality pigment-based inks currently available.  When permanence is a major concern, it is best to evaluate the current array of inks and papers before buying a printer to make sure everything is compatible and capable of producing the desired results.  Using papers and inks from different manufacturers is not recommended because manufacturers only test, rate, and guarantee permanence based upon their own system of papers, inks, and printers.  Choosing papers and inks from different manufacturers may produce the visual results one is looking for, but be sure the combination has been tested for maximum longevity (see Chapter 9 for factors affecting permanence).

 

Printing Methods & Output Issues

 

Desktop Ink-jet Printers

Desktop Ink-jet printers are inexpensive and use water-soluble inks and plain paper to make color prints. Better-quality paper will yield higher-quality images.  Some dye-based ink-jet printers produce prints that are impermanent and can, without protection, fade within 6 months.

 

Iris Print

The iris printer was the first printer used in digital fine art reproduction. Iris prints are a type of ink-jet print produced by spraying millions of fine dots of ink per second onto paper.  Created on a spinning drum, these gallery-quality prints can be made on virtually any material that will accept ink. The iris printer uses dye-based inks that produce some of the most vibrant and widest tonal values available. Depending on the type of ink, paper, and coating, such prints could have a life span ranging from as little as 6 months but generally iris prints are made to last decades. Iris prints where once the standard for high quality fine art reproductions but now has become a special purpose niche process. Although iris prints still represent the standard in which most digital prints are measured against.

 

Light-Jet

A LightJet or Lambda printers are brand names for printers that expose a digital image directly to color or black-and-white photographic paper using red, green and blue laser beams.  The resulting images are processed in regular photographic chemistry and therefore possess the same surface and permanence properties as traditional photographic prints.  LightJet prints are extremely sharp and very close to continuous tone because the LightJetÕs resolution would exceed 4000 dpi when compared to conventional half-tone printing.

 

Giclee Printing

Giclee, French for squirt, is a chic phrase for ink-jet printing.  Technically, even an inexpensive ink-jet printer produces giclŽe prints.  GiclŽe was first associated with Iris printers, which initially defined the digital fine art print market.  It was used to appeal to print connoisseurs who expected state of the art ink-jet printing with a certain level of permanence, but the term is not regulated and hence carries no warranties of any sort.

 

Mural-Size Prints

Creating photographic high-quality digital images is a reality for both the consumer and professional and can be seen in art worldÕs embrace of mural-size prints.  Even though digital cameras can exceed the sharpness of 35mm film cameras, the enlarging limitations remain constant.  Digital photography is not a magic bullet for making large prints from small cameras.  A blow-up from any type of 35mm equivalent media will show a loss of sharpness due to the increase in grain or pixelazation in proportion to the size of the enlargement.  Once affordable digital image sensors become available in medium and large formats, film will eventually become obsolete.

            Until this occurs, the best practice for making big fine art digital imagery is to record the image on a large format film and scan the film at the highest possible resolution.  Such prints require film scans, in excess of 4000 dpi and up to 8000 dpi, along with professional scanners and printers.  Making digital prints exceeding the capabilities of desktop printers, 13inches in height widths up to 40 inches, require floor model photo quality ink-jet printers.  Many of these printers are capable of printing up to 64 inches in height and widths as long as the roll of papers will allow (lengths can exceed 100 feet).

 

Mixed Digital Media

With the availability of high quality, large-format printers and a wide variety of printing materials the possibilities of digital mixed media have just begun to be explored.  Photographers have always experimented with the surface of the print, some by applying pigment to the surface others by collaging different photographic images and materials together.  All of these methods can be brought together using the digital print as well.  In addition to traditional glossy paper, manufacturers have developed materials such as artist canvas that can be run through a digital printer and then be painted on with acrylic or oil paints like a conventional canvas.  Materials, such as Polysilk cloth, can be printed on and then become waterproof, which allows them to be exposed to the elements or even washed.  Other materials include translucent and transparent films that can be used as backlit prints, as photographic negatives or in mutilayered images.

 

Preparing the Digital Print for Mixed Media

New developments in digital media are currently being driven by the advertising industry.  Most of the store displays, such as ads found in supermarkets, are now being produced on these large format printers.  Artists have to be aware of the demands of the advertising industry when using these new materials.  Advertisers want their materials to be sturdy enough to be walked on or displayed outdoors, but they are not necessarily interested in images that will last more than a few months or a few years.  Luckily many of the same qualities that make an image last for 25 months outdoors will allow those same prints to last years or decades when they are displayed indoors.

One thing that imagemakers can do to protect their images from damaging UV or when preparing images for mixed media applications, such as acrylic or oil paint, is to seal the surface with a spray or liquid coatings.  These coatings are water or solvent based and can be used with water sensitive inks.  Since many of these coatings can yellow or crack over time, testing a particular combination before use is recommended.

 

Working With a Computer

As a camera condenses a three-dimensional scene into a two-dimensional representation, the computer seamlessly combines different media into a virtual representation, retaining the qualities of some and eliminating the qualities of others.  Anything that can be done with a camera, paintbrush, or drafting set can be replicated on a computer.

Large, high-resolution images require extra processing time and plenty of available hard-drive space to operate efficiently.  A 100 MB file should have at least five times that amount (500MB) of free hard drive space to make use of the imaging software tools and the filters.

The computer is a powerful tool for experimenting with ideas and design, but it is not always the best way to produce an image.  Images stored on silver-based film provide a tremendous amount of permanent information that is easy to access, and economic to store.  If you are not planning to significantly manipulate the image, a wise choice still could be the silver-based photography.  

The Color Monitor

All monitors use an additive RGB color system (see Chapter 1).  Any combination of these light primaries always produces a lighter result.  Since light is transmitted from the image, the colors tend to be more saturated and luminous.  The printed image uses a CMYK subtractive system to form an image on a sheet of paper.  Any increase in pigment density subtracts the initial amount of light, producing a darker result.There is an inherent visual difference between images seen on your monitor, other monitors, and output devices.  Sophisticated monitors allow for color correction as well as contrast and brightness adjustments, but these only affect how the image appears on your monitor and not other monitors and/or paper output.  Color management hardware and software is available to help control the color balance between monitors and output.  

 

How Monitors Show Color

Depending on the monitor size and the amount of video memory (VRAM) it is possible to see and manipulate millions of colors with image-processing programs.  All video monitors represent color by displaying minute RGB dots, which are displayed on the monitor as pure color.  All other colors shown on-screen are a mixture of pixels used to approximate the color needed.  In addition to full color, images can be produced as a gray scale, which produces 256 shades of gray, or bitmap images, which are purely black-and-white.

 

What Is Bit Color?

Bit depth describes the number of bits (the smallest unit of information on a computer) assigned to each pixel and refers to the number of shades of gray or the number of colors that can be represented by a single pixel.  The greater the number of bits (2, 4, 8, 16, 24, 32 or 64) the greater the number of colors and tones each pixel can simulate (see box 8.1).  The bit depth of your computerÕs display is the number of different colors it can show at any given time.  The size of the display and the amount of video RAM you have on the graphics card controls bit depth. 64-bit color is the highest level of color a computer can produce.  24 bits and above create color variations well beyond the range of human perception.  Even though human perception is limited to 24 bits and below, 32 and 64 bit color can improve color accuracy and correction on screen.

 

 

Color Management (ICC Profiles)

In 1993 a group of eight software and digital output device manufacturers formed the International Color Consortium (ICC) to establish and maintain a set of international color standards.  The group introduced a standard device profile format, known simply as ICC, to define how different color devices, often made by different manufacturers, produce color images.  An ICC profile is a file that describes how a particular device reproduces color (printers or monitors).  These profiles map onto an image file the characteristics of different output devices with their limited color spaces making the output of images from varying devices predictable and observable.

 

Profiles, Profiles and More Profiles

In the digital environment every workstation has a unique Òprintable color spaceÓ sometimes known as Òcolor gamutÓ.  ICC profiles are small, digital files that help the computer determine the actual viewable and printable color space of the working environment.  These files are sometimes pre-loaded in an image of software program, but many need to be loaded based on the device.  Color space is determined by everything that goes into making the image including: the camera or scanner (input), the type monitor (viewable color space) and the printer along with its specific combination of inks and paper (output).  The ICC profiles Òre-mapÓ or reassign a new color value to a digital image when color values are detected outside the viewable or printable color space.  Sometimes the shift is not severe or even detectable.  The standard ICC profiles, called Ògeneric profiles,Ó are designed as a Òbest guessÓ method of normalizing many variables over the widest variety of possible environments and can do a good job.  Factory ICC profiles are best and can reduce time and effort when color correcting, but not always.

Anyone with conventional color darkroom printing experience will see the same functionality between determining the correct filter pack and using ICC profiles.  In conventional color printing a series of cyan, magenta and yellow filters are used to correct color balance based on the type of film, light source, paper, temperature, and chemicals.  The ICC profiles are digital equivalent.  In a controlled working environment with well-maintained equipment a good understanding of ICC color management can minimize the color correction process with digital images.  Just as in conventional color printing, ÒtweakingÓ the color balance is a continuous process.  ICC profiles are based on the monitor settings, such as contrast, brightness, color temperature, tint, and RGB, and have their place in making critical work.  In a controlled working environment with the proper software and color calibration equipment, the color calibration of the monitor to the printer can be done very precisely.  In a group lab environment where the monitor controls and room lighting are constant flux, it is usually easier and quicker to first print a digital image file that contains both a gray scale and color scale chart.  This print is compared directly to the monitor and the necessary adjustments are made to the monitor to match the print.  Although this color management style is not empirical, it works well to compensate for the numerous unexpected changes that constantly occur in a group work environment.  Also, regardless of what a calibration program states, color response is subjective and it is our eyes that ultimately determine whether a color print achieves its desired results.

 

Other Digital Colors

Many software applications allow for the manipulation of color according to its hue, saturation, or luminosity (HSL) or through a licensed color system such as Truetone¨ or Pantone¨.  These last two systems allow for the most understandable color manipulation on the computer.  Process color, or CMYK, is the traditional printing method of lithographic printers.  This set of subtractive primary color is the system used by most color printers.  Many output devices cannot print all the colors a computer is capable of processing.  Some software packages will warn you if a particular device cannot print a selected color.  Computer users can make color separations for printing using the CMYK mode.  When switching from RGB to CMYK the computer dulls the screen colors to simulate a subtractive print.  High-end multi-color printers rely on RGB to manage all their possible color options.  Duo-tone effects, applying a second accenting color, are also possible.

 

Digital Memory

 

RAM

When a program begins, its contents are loaded into random access memory (RAM). Instructions the computer needs to perform its tasks are stored and processed in RAM chips, sometimes called memory chips, that come in a variety of sizes, pin configurations, types, and formats.  The amount of RAM a computer has directly affects its performance and capabilities and is easily expanded.  Most software applications include minimum memory requirements on their printed material.  However, to effectively run the program you may need much more RAM so it is prudent to research programs before purchasing them.

 

ROM

Permanently installed in the computer, read only memory (ROM) contains the basic instructions the computer needs to start up and to draw objects on a screen. Unlike RAM memory, ROM is unalterable.

 

Hard Disk

The hard disk, usually installed inside the computer, is where applications and files are stored.  Since image files are often larger than the available RAM, some software applications use the hard disk to temporarily store information.  The program shuffles information from the hard disk (the scratch disk) into RAM, where it is processed.  This enables the program to complete complex operations and functions, such as ÒundoÓ and Òpreview.Ó  The scratch disk can take up to five times as much space as the original image because it stores several different versions of the image.  The computerÕs hard disk must have enough free space to accommodate these temporary files.

Basic Digital Imaging Functions and Tools

 

Top Main Menu Options

Regardless of the imaging program, there are many common and unique categories located in the top Main Menu that offer access to many functions for editing images. The most common categories are File, Edit, View, Insert, Layer and Filter. Within these categories there are hundreds of selections, that when used in combination with the Toolbar, can create several thousand ways to manipulate an image.

 

Cut and Paste Function

The ability to replicate and move information is the essential power of the computer.  Cutting and pasting is possible between files made on different pieces of software as well as between documents made on the same software.  The data structure of the information is not always compatible.  Most well developed software applications have a set of procedures, usually located under Edit in the Main menu, for converting and opening files produced by different applications.

 

Scale & Size Function

Scale, one of the primary clues to depth perception, can be manipulated to change the context or to create an image that challenges the viewerÕs assumptions.  An entire image or parts of an image can be foreshortened to simulate perspective or stretched to fit into a defined area.

            Size controls, usually located under Edit in the Main menu, usually refer to image size or canvas size.  Both make the image larger or smaller when outputted, but altering the canvas size allows for the creation of blank drawing space (or crops the image) while altering the image size affects the overall dimensions of the image.

 

Digital Filter Function

An image can also be manipulated through a serious of functions called Filters usually located in its own Main Menu category. All programs offer a wide variety of filters built into the program but many third party filters, known as plug-ins, can be purchased and added to the default filter list.  Common filter effects are pixelate, blur, mosaic, distort, charcoal, reticulation and many other artistic effects. In the nineteenth century, photographers turned to the aesthetic strategies of painting for guidance.  Today, software manufacturers have done the same, producing effects packages that transform digitized images into simulated paintings.  As imagemakers continue to discover an original digital aesthetic, there will be less of a reliance on older mediums and filters that simulate them, allowing an authentic digital syntax to emerge and grow.

 

Common Toolbar Icons for Additional Photo-editing

Many of the common editing tools began in Photoshopª and have since migrated to other programs. The various tools are located in a floating toolbar that defaults to the right or left side of your screen. The tools described here only represent the most universal and common. Please refer to the manufacturers manual or the applicationÕs Help Menu for complete and detailed descriptions of all tools. Many of the visible tools on the toolbar have hidden options that are revealed by simply using Click-Hold or Option-click the visible icon, depending on program. Also, each tool has editable options that are usually displayed in an Options Bar underneath the top Main Menu on the screen when tool it is active.  The Options Bar is a convenient way to change many options related to the active tool such as: brush size, type of gradient, font size, transparency and colors.

 

Changing Mouse Pointer

When tools are selected, the mouse pointer matches the tool icon. Many of the drawing and painting tools are circles, which represent the selected width. Each cursor has a hot spot where the effect begins, for example: the tail of the lasso's loop for the Lasso tool is where the selection begins.

 

Option/Shift/Command keys

Knowing when to the use the option, shift or command keys in conjunction with the active tool will be necessary to use many of the tools and their functions. For example: using the Option key with the Zoom tool changes the mouse pointer to a plus or minus allowing one to Zoom in or Zoom out of the image on screen. Also, using the shift key with the Magic Wand allows you to add to your previous selection allowing one to group many selections.

 

Bit Color

 

2bit = black & white

4bit = 16 color

8bit = 256 color

16bit = 32,0000 colors

32bit = millions of colors (16.8 million)

64bit = billions of color (4.2 billion)