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The Ultimate Guide to Digital Imaging

Vocabulary

The Ultimate Guide to Digital Imaging

Color, File Prep, Formats & More

Digital is the default medium that today’s photographers, artists and brands rely on to produce eye-catching, statement-making imagery. While digital may seem “easier” than traditional methods in many ways, it is also much more complex. Digital printing is both an art and a science, with countless nuances being balanced behind the scenes. As one of the few early photographic labs that has managed to adapt to and thrive in the digital age, Duggal Visual Solutions shares creatives’ passion for perfection in every aspect of digital image reproduction. This comprehensive guide to digital imaging serves as a how-to, how-it-works, did-you-know and in-case-you-forget, all in one.

Printing Terms and Concepts

Primary Colors RGB and CMY

There are two separate sets of primary colors in printing: additive color and subtracted color. Additive color is the color space for mixing light to create color. Monitors use additive color. Subtractive color is the color space used for pigments, inks or paints. All prints are subtracted color.

For additive color, the primary colors are Red, Green and Blue (RGB), each representing a third of the visible color spectrum of light. When you combine equal amounts of Red, Green and Blue light together, they create white light. Changing the intensity or amount of each color creates color and lightness variations.

The subtracted primary colors are Cyan, Magenta and Yellow (CMY). Mix equal amounts of Cyan, Magenta and Yellow pigment, and you have created Black. All other colors including Red, Green and Blue can be mixed from these three primary colors. In printing, K or black ink is included to add extra density to the dark areas. In theory, if we could produce inks that were a pure Cyan, Magenta and Yellow, we could produce all of the visible colors with just three inks. Unfortunately, inks are not pure and contain other colors, making it impossible for them to produce clean, vibrant colors. For instance, most inks called Cyan actually have Magenta in the ink and thus do not produce a clean Cyan color such as the color of a Caribbean Sea.

Profile, Formats and File Size for Digital Files

When checking a digital file, you should note three important characteristics: profile, format and file size. This information will give you a good idea of the quality of the final print and how large it can be reproduced.

The profile tells you the color space and the color model that the print was created in, such as Adobe 1998 (which is a RGB color space) or GraCol a (CMYK color space). Different profiles have different quality and range of colors.

The format is the way the digital file is stored. Some formats use compression to make the file easier to store by reducing the size. Common formats are JPEG, TIFF and RAW. File format can affect print quality, as well as the ability to adjust or correct the image.

The file size will be in megabytes, which essentially tell you how much digital information the file has. Each megabyte is 1024 kilobytes of data. The more megabytes, the more digital information, and the larger a print can be made.

Profiles for Digital Files

 Color Profile

A color profile is a numerical model of a color space. A color profile is needed to display and print accurately. Some profiles capture the maximum amount of colors and information, while others intentionally limit color to match the printing process or display that the file is being used for. For instance, Swop profiles limit the colors to match the colors that a web press can achieve. Matching the profile to the final use creates a more predictable result.

Adobe 1998

Adobe 1998 is a RGB color space that can reproduce approximately 50% of all visible colors, more than most printers can print. It is one of the most popular profiles because it captures so much information and color.

SRGB

SRGB can reproduce 35% of visible colors. The gamut is very close to most monitors and displays. Images on line are usually SRGB.

SWOP

Specifications for Web Offset Publication, or SWOP, is a specification for printing in the United States on Web presses. The SWOP organization developed SWOP to standardize the printing process and improve consistency. Most magazines are printed using SWOP. The profile is used to replicate the density and color on a SWOP printing press. Because the SWOP printing process has limited color saturation, the files also are limited in the range of colors.

GraCol

General Requirements for Applications in Commercial Offset Lithography, or GraCo,l is a specification for sheet fed printing. The specification defines ink specifications based on ISO standard defined CMYK inks and paper grade. GraCol is similar to SWOP but has a little richer color and slightly brighter paper.

Formats for Digital Files

TIFF (Tagged Image File Format)

TIFF is one of the most popular file types because it is a lossless format that enables embedded profiles and multiple players.

JPEG

JPEG is the most common format used in digital cameras. Unfortunately, the compression it uses can cause loss of information and detail. The file does not have the amount of information or the ability to process as a camera RAW file. When you shoot in JPEG, the camera converts the RAW data into JPEG automatically, without any consideration for the best option.

RAW

RAW or camera RAW files contain all the information that was captured by the sensor in the camera or scanner. Unlike JPEG or TIFF tiles, RAW files can be “processed” multiple times to create a single file that optimizes all data. RAW files are not print ready. They must be processed and saved in another format such as TIFF before printing.

PDF

PDF, or Portable Document File, is used to create documents that do not need the software they were created in to open or view. Most browsers can open PDFs. Because PDFs can contain all types, fonts and images, they are a good way to share files.

File Size

Megabyte

A megabyte is 1025 kilobytes of information. When you see the file size in megabytes, it has figured in the size, resolution and color space. An 8×10 CMYK file at 300 DPI is 27.5 megabytes, as is a 16×20 CMYK file at 150dpi. The 16×20 print is twice the size of the 8×10, but half the DPI. If we were in RGB, it would be 20.6 megabytes. The RGB file is smaller than the CMYK file because it has only three colors, where the CMYK has four.

Megapixel

Megapixel is a term most often used to describe the digital capture size of a camera. For every megapixel, you have 1 million pixels. If your camera captures 3507 pixels wide by 2338 pixels high, it is an 8.2 megapixel camera.

DPI

DPI (dots per inch) is a term to quantify how many printed dots are used by a printer in creating a print. The higher the DPI, the better the quality. Files sizes are sometimes described by DPI as well. This can be confusing because you need to know the size of the file and DPI to understand how much data the file has. It is much easier to use megabytes. For computer screen resolution, PPI (pixels per inch) is used to describe the resolution because the images on monitors are created with pixels instead of printed dots.

Compression

Compression is used to reduce file size. There are two types of compression: Lossy and Lossless. When you use lossless compression, the quality of your original is maintained. Lossy compression may lose detail and information to obtain a smaller file.

File Interpolation

Using software, pixels are added to create a larger file by mathematically averaging the data between two pixels to create a third pixel. Although the file gets larger and may look better when enlarged, it has not created any new original data. A larger digital photo will always look better than an image that was smaller and enlarged by interpolation.

Pixel

The term, pixel comes from combining the words, picture and element. Pixels are the smallest display unit on a computer screen. Each pixel has three channels, one for each of the RGB colors. Most monitors’ pixels are 8 bit, which can create 256 distinct colors in each of the RGB channels. Newer high-end displays offer 10 bit color, which translates to 1024 pixels per RGB channel.

Types of Prints

Large Format Printing

Large inkjet printers can print up to 16 feet wide. Many substrates ranging from vinyl to wallpaper can be printed on to create giant color prints. The quality of large prints depends on the quality of the original file sent to the printer, the DPI that the printer can print, and the color range of the inks the printer uses.

Giclee

The word Giclee, which means “splash” in French, is used to describe high quality archival inkjet prints. Many types of “art” papers can be used for giclee printing.

Dye-Sublimation Prints

Dye-sublimation allows us to permanently print on fabrics. These large format prints can be used in lightboxes, outdoor banners, custom fabrics and more. They can also be folded for easy shipping.

C-Print / Duraclear/ Duratrans

The original digital photo printing process was introduced in the 1950s by Kodak as the “chromogenic color print” or “C-print.” These prints use silver halide and dye couplers. The light sensitive plastic papers were originally exposed using enlargers to project negatives onto the C-paper. Most C-prints now are exposed by digital printers from digital files using lasers or LED. After the C-Print paper is exposed, the paper must be processed in photographic chemicals that develop the image. Besides paper C-prints, there are also clear base prints called Duraclear and Duratrans that have a white transparent base.

Lighting for Viewing Prints

Color Temperature

The color of light is measured in kelvin degrees to describe the color temperature of a light source. 5000K is close to daylight, and warmer Tungsten light is around 3200K. The lower the kelvin, the redder the light, and the higher the kelvin, the bluer the light. Different color lights can drastically change how a print looks. It is very important to know the color temperature of the light that a print will be viewed with.

Metamerism

When two materials or prints appear to match under one light source but differ under another light, the phenomenon is called metamerism. Metamerism is caused when light sources are not full spectrum. Two light sources may appear similar in color when viewed, but could be missing certain parts of the color spectrum. The missing color causes the metamerism.

Types of Printers

Lambda / Lightjet

Years ago, negatives were projected onto photographic paper using enlargers, and then processed in photographic chemicals to create a print. Lambda and Lightjet replaced the enlarger by projecting digital images using lasers onto the same photo paper. After exposing the paper, the prints need to be processed in photographic chemicals.

Web Press

Web presses print on continuous rolls of paper or other substrates. These presses are used for large volume print runs such as newspapers and magazines. The CMYK inks are not very pure, so the results from a SWOP press are less colorful than higher quality printers such as inkjets.

Sheet-Fed press

Sheet-fed presses print on individual sheets of paper, unlike the Web press that uses a roll. This allows the printer to go slower, which increases the ink density of the print. Sheet-fed presses are normally used for smaller quantity and higher quality print runs.

Authored By:

Jerid O’Connell

VP of Creative Services, Duggal Visual Solutions

 About Duggal Visual Solutions

Duggal Visual Solutions, Inc. was incorporated in 1963 and is an award-winning global supplier of printed visuals, custom displays and multimedia solutions. For more than 50 years, Duggal has served as a trusted advisor and partner in helping the world’s leading image-makers communicate visually with their audiences and customers.

Our clientele is widely spread among top global retailers, Fortune 500 corporations, museums, galleries, non-profit organizations, photographers, visual artists and designers. Our cutting-edge production equipment, 24-hour facilities, and seasoned industry veterans combine to offer a comprehensive suite of visual solutions for projects of all sizes and parameters. From in-house design and production to shipping and installation anywhere in the world, the Duggal team is dedicated to providing the highest level of service and quality.

To learn more, visit www.duggal.com