Output Dictates Input

As illustrated in the digital workflow map from the previous lesson, there is a process that needs to be decided before even the first steps of a project commence. Depending on how the final artwork is intended on being displayed, the original material will need to be scanned, photographed, or imported at particular resolutions and color modes.

Pixel Resolution

Photoshop is the industry standard for Rastered artwork. In recent years it has also begun to include features that allow for the creation of some Vector artwork. Both of these file classifications have different technical aspects that effect printing.

Rastered files are composed pixels and are also referred to as bit-mapped art (also: bitmaps, bitmap files). They are generated in Photoshop are bound to the metrics between pixel resolution and document dimension.

Read: Image Resolution

When a bit-mapped image changes size, the relationship between it’s pixel resolution (measured in pixels per inch) and it’s pixel dimensions change. When an image is scaled bigger (the pixel dimensions become greater), the image will loose quality (the pixel resolution becomes lower).

When bitmap files are scaled above 100% the resolution lessens, resulting in what is referred to as ‘pixelation’ – a loss in visual detail.

Vector artwork is composed of visually presented mathematical equations. They are primarily generated in Adobe Illustrator and sometimes with the vector tools offered in the later versions of Photoshop. Vector files and are resolution independent; they can be scaled up or down infinitely with no loss in detail.

RGB vs. CMYK

Color is reproduced differently on computer screens than it is on paper. The fundamental discrepancy means that ‘what you see is not what you get” in term of color reproduction on paper from your computer monitor. (See Color Management below for more.)

RGB
Red, Green and Blue are the three colors of light used to produce the visible spectrum of color on a computer screen.

CMYK
Cyan, Magenta, Yellow, and Black( K) are the four primary colors of ink used to produce color on paper.

All computer monitors display color in RGB. All printers use CMYK ink-sets to remake the colors on screen to images on paper. While many desktop printers now accept and print files with RGB color values, these values are still converted to CMKY during the printing process.

To understand the differences between RGB and CMYK the difference between additive and subtractive color theory needs to be examined.

Resolution & Color Modes for Printed Artwork

Artwork whose output is via a printer needs to be saved in CMYK format*, and be much higher resolution that that of art displayed digitally. Typically all files bound for printing are made and saved at a minimum 300 ppi

*Note: Nearly all desktop printers (like the ones used for class) are ‘pro-sumer’ level printers, and are designed to accept RBG files to reduce user error, which are converted into CMYK when printed. For more about this topic visit: photo.net – Epson 1280 etc. CYMK or RGB printer?

Resolution & Color Modes for Screen and Web Art

Artwork whose output is to a computer screen (via the Web, CD/DVD, iPod, touch screen kiosks [ATMs, self check-outs, Airport check-in…]) needs to be saved in RGB format and require a resolution of 72 pixels per inch (72ppi or a ‘resolution of 72’)

Acquiring Artwork Via a Scanner

Nearly all scanners can be accessed within Photoshop, using a protocol known as TWAIN

Careful attention should be paid when scanning to create both the proper resolution and target size.

There are two types of functionality that most desktop scanners can provide – reflective – or flatbed scanning, and transparency – or film scanning. Both still require the same attention to resolution and target size to create a technically suitable file to be sent to photoshop or saving.

Importing Art From Digital Cameras

Most digital cameras can interface directly with Macintosh computer without any additional software – the image files can be copied directly from the camera’s CF card or SD Card to your personal hard drive and accessed in Photoshop or Bridge.

Importing Art From Other Software

Artwork sometimes originates in software other than Photoshop, and can easily be imported, placed, or even pasted into a Photoshop file.

When importing vector files (Adobe Illustrator Files) or PDF files (Adobe Acrobat) the files will likely need to be ‘rasterized’. This process commits the artwork to a bitmap. Be sure to choose an appropriate resolution and dimensions – the art cannot be ‘upsized’ or scaled larger after this step.

Saving Artwork in Photoshop

There are several formats that Photoshop can generate. Each has it’s own qualities and serve different purposes.

Popular Image File Formats

PSD – the native format for Photoshop

PSD (Photoshop Document) is the preferred file format for artwork created or edited in photoshop. It the only file format that will respect all the editing features available, including layers, adjustment layers, layer effects, masking etc. It is an uncompressed format and is the best way to archive your work. It is likely not the best format for output except for direct printing to desktop printers – the files are incompatible with many other programs, and are far too big to use on the Web.

JPEG – A common multipurpose filetype.

JPEG (Joint Photographic Experts Group) files are a lossy format (in most cases). The DOS filename extension is JPG, although other operating systems may use JPEG. Nearly all digital cameras have the option to save images in JPEG format. The JPEG format supports 8 bits per color – red, green, and blue, for 24-bit total – and produces relatively small file sizes. The compression when not too severe does not detract noticeably from the image. But JPEG files can suffer generational degradation when repeatedly edited and saved.

TIFF – A larger file for printing

TIFF (Tagged Image File Format) is a flexible image format used for printing, and uses a filename extension of TIFF or TIF. TIFF files are much bigger in file size than JPEGs, but like JPEG, the TIFF format can be lossy or lossless. Some types of TIFF files offer relatively good lossless compression for bi-level (black and white, no grey) images. Some high-end digital cameras have the option to save images in the TIFF format, using the LZW compression algorithm for lossless storage. The TIFF image format is not widely supported by web browsers. TIFF is still widely accepted as a photograph file standard in the printing industry. TIFF is capable of handling device-specific color spaces, such as the CMYK defined by a particular set of printing press inks.

RAW – a robust format made by digital cameras

RAW refers to a family of raw image formats that are options available on some digital cameras. These formats usually use a lossless or nearly-lossless compression, and produce file sizes much smaller than the TIFF formats of full-size processed images from the same cameras. Unfortunately, the raw formats are not standardized or documented, and differ among camera manufacturers. Many graphic programs and image editors may not accept some or all of them, and some older ones have been effectively orphaned already. Adobe’s Digital Negative specification is an attempt at standardizing a raw image format to be used by cameras, or for archival storage of image data converted from proprietary raw image formats.

GIF – a compressed image for non-photographic for the Internet graphics

GIF (Graphic Interchange Format) is limited to an 8-bit palette, or 256 colors. This makes the GIF format suitable for storing graphics with relatively few colors such as simple diagrams, shapes, logos and cartoon style images. The GIF format supports animation and is still widely used to provide image animation effects. It also uses a lossless compression that is more effective when large areas have a single color, and ineffective for detailed images or dithered images.

PNG – an advancement over a GIF, for Images on the Internet

The PNG (Portable Network Graphics) file format is regarded, and was made as, the free and open-source successor to the GIF file format. The PNG file format supports true color (16 million colors) whereas the GIF file format only allows 256 colors. PNG excels when the image has large areas of uniform color. The lossless PNG format is best suited for editing pictures, and the lossy formats like JPG are best for final distribution of photographic-type images because of smaller file size. Many older browsers do not yet support the PNG file format, however with the release of Internet Explorer 7 all popular modern browsers fully support PNG.

BMP a basic image file for Windows compatibility

The BMP file format (Windows bitmap) is used internally in the Microsoft Windows operating system to handle graphics images. These files are typically not compressed, resulting in large files. The main advantage of BMP files is their wide acceptance, simplicity, and use in Windows programs.