DIGITAL FILE FORMATS + more information about digital Files
FILE MANAGEMENT
Everyone should have a portable storage device (USB Flash drive or hard drive) or use the Art & Design Data Server.
Files need to be "managed", i.e. arranged and sorted by some functional and consistent system.
Notes on good file management
1. Obvious - make sure that you are saving/copying your files onto your portable drive (or the Data Server), files stored on the desktop computer in the labs will NOT be saved after you log out.
2. In your storage device, the following is recommended:
A. Create a folder named "Image Practice" or "arts341"
B. As you create files for certain projects, create folders named for the projects those files belong to - you should end up with a folder for each project, for example.
C. Within your respective project folders, you should also create deeper levels of order. Folders that distinguish between Photoshop (un-flattened) files and flattened printable files is a good idea. A folder for source images is also recommended.
3. Naming files. It is recommended that you DO NOT use space and special characters (other than hyphens and underscores) in the names of your files. Come up with a system for differentiating words in compound titles: "myPhotoshopFile.psd" or "Red_car.jpg" for example.
4. When working in Photoshop, NEVER trash your unflattened files - Save both your print/web-ready and photoshop files. If you need to edit the image for any reason, you definitely want the photoshop file with all your layers.
BASICS OF DIGITAL IMAGE FILES
Resolution
The pixel dimensions (image size or height and width) of a bitmap image is a measure of the number of pixels along an image's width and height. Resolution is the fineness of detail in a bitmap image and is measured in pixels per inch (ppi) or another unit of measurement (cm, mm, etc). The more pixels per inch, the greater the resolution. Generally, an image with a higher resolution produces a better printed image quality.
Remember though that screen resolution is always low (usually 72ppi), so high resolution images on monitors are reflected by their scale - you can zoom in on a high res digital image, retaining more detail that a low res one.
This is different, but related to print quality, measured in dots-per-inch (dpi) which is controlled by the printer.
File Types
PSD: Photoshop format (PSD) is the default file format and the only format, besides the Large Document Format (PSB), that supports most Photoshop features. Because of the tight integration between Adobe products, other Adobe applications, such as Adobe Illustrator, Adobe InDesign, Adobe Premiere, Adobe After Effects, and Adobe GoLive, can directly import PSD files and preserve many Photoshop features. For more information, see Help for the specific Adobe applications.
When saving a PSD, you can set a preference to maximize file compatibility. This saves a composite version of a layered image in the file so it can be read by other applications, including previous versions of Photoshop. It also maintains the appearance of blended layers in the future.
16-bits-per-channel and high dynamic range 32-bits-per-channel images can be saved as PSD files.
JPG: JPG (Joint Photographic Experts Group) is what is called a "lossy" format, as it is based on a compression schema that decreases file size by "recording" only certain information about the image. Lossy means that the image looses quality each time it is saved and compressed. JPGs are 24-bit color files. JPGs are most useful for photographic images used on the web.
PNG: Portable Network Graphic is a lossless form of image compression - much like a GIF. PNGs save only the color information necessary (or selected) for the image quality in question. This form of compression is called "indexed color" - meaning exact color information is "recorded" in the file, so it reproduced exactly each time it is saved/copied. PNGs can save alpha transparency in 32-bit mode (unlike GIFs). Both PNGs and GIFs are most useful for graphics and images with large areas of solid colors on the web.
GIF: Graphics Interchange Format (sometimes called CompuServe GIF, after the company that developed it in 1987). It only supports up to 8 bits per RGB channel (thus 256 colors total) and is a lossless format. It is primarily good for solid and limited color range images. It can also save limited info for animations.
TIFF: Tagged-Image File Format (TIFF, TIF) is used to exchange files between applications and computer platforms. TIFF is a flexible bitmap image format supported by virtually all paint, image-editing, and page-layout applications. Also, virtually all desktop scanners can produce TIFF images. TIFF documents have a maximum file size of 4 GB. Photoshop CS and later supports large documents saved in TIFF format. However, most other applications and older versions of Photoshop do not support documents with file sizes greater than 2 GB.
TIFF format supports CMYK, RGB, Lab, Indexed Color, and Grayscale images with alpha channels and Bitmap mode images without alpha channels. Photoshop can save layers in a TIFF file; however, if you open the file in another application, only the flattened image is visible. Photoshop can also save annotations, transparency, and multiresolution pyramid data in TIFF format.
In Photoshop, TIFF image files have a bit depth of 8, 16, or 32 bits per channel. You can save high dynamic range images as 32-bits-per-channel TIFF files.
About Compression
Graphics file formats differ in the way they represent image data (as pixels or vectors), in compression techniques, and which Photoshop features they support. With a few exceptions (for instance Large Document Format (PSB), Photoshop Raw, and TIFF), most file formats cannot support documents larger than 2 GB.
Note: If a supported file format does not appear in the appropriate dialog box or submenu, you may need to install the format’s plug-in module.
About file compression
Many file formats use compression to reduce the file size of bitmap images. Lossless techniques compress the file without removing image detail or color information; lossy techniques remove detail. The following are commonly used compression techniques:
RLE (Run Length Encoding)
Lossless compression; supported by some common Windows file formats.
LZW (Lemple-Zif-Welch)
Lossless compression; supported by TIFF, PDF, GIF, and PostScript language file formats. Most useful for images with large areas of single color.
JPEG (Joint Photographic Experts Group)
Lossy compression; supported by JPEG, TIFF, PDF, and PostScript language file formats. Recommended for continuous-tone images, such as photographs. JPEG uses lossy compression. To specify image quality, choose an option from the Quality menu, drag the Quality pop-up slider, or enter a value between 0 and 12 in the Quality text box. For the best printed results, choose maximum-quality compression. JPEG files can be printed only on Level 2 (or later) PostScript printers and may not separate into individual plates.
CCITT
A family of lossless compression techniques for black-and-white images, supported by the PDF and PostScript language file formats. (CCITT is an abbreviation for the French spelling of International Telegraph and Telekeyed Consultive Committee.)
ZIP
Lossless compression; supported by PDF and TIFF file formats. Like LZW, ZIP compression is most effective for images that contain large areas of single color.
Digital Color
Bit depth specifies how much color information is available for each pixel in an image. The more bits of information per pixel, the more available colors and more accurate color representation. For example, an image with a bit depth of 1 has pixels with two possible values: black and white. An image with a bit depth of 8 has 28, or 256, possible values. Grayscale mode images with a bit depth of 8 have 256 possible gray values.
RGB images are made of three color channels. An 8-bit per pixel RGB image has 256 possible values for each channel which means it has over 16 million possible color values. RGB images with 8-bits per channel (bpc) are sometimes called 24-bit images (8 bits x 3 channels = 24 bits of data for each pixel).
In addition to 8-bpc images, Photoshop can also work with images that contain 16-bpc or 32-bpc. Images with 32-bpc are also known as high dynamic range (HDR) images.
See an example of differences and chart.
Bitmap Vs. vector graphics: A bitmap file contains information about each pixel that makes up the image - which means that increasing the scale of an image decreases its resolution and increases the amount of memory used. Photographic forms of images are bitmaps.
Vector graphics are created through mathematical formulas that determine line size, radius of arcs and color. Vectors can be reduced and enlarged without resolution degradation or proportion changes. Illustrator and InDesign are examples of print based vector apps. Flash uses vectors on the web.
The web is an RGB environment, low resolution (72 ppi), so any images you download are probably low res and RGB.
Everyone should have a portable storage device (USB Flash drive or hard drive) or use the Art & Design Data Server.
Files need to be "managed", i.e. arranged and sorted by some functional and consistent system.
Notes on good file management
1. Obvious - make sure that you are saving/copying your files onto your portable drive (or the Data Server), files stored on the desktop computer in the labs will NOT be saved after you log out.
2. In your storage device, the following is recommended:
A. Create a folder named "Image Practice" or "arts341"
B. As you create files for certain projects, create folders named for the projects those files belong to - you should end up with a folder for each project, for example.
C. Within your respective project folders, you should also create deeper levels of order. Folders that distinguish between Photoshop (un-flattened) files and flattened printable files is a good idea. A folder for source images is also recommended.
3. Naming files. It is recommended that you DO NOT use space and special characters (other than hyphens and underscores) in the names of your files. Come up with a system for differentiating words in compound titles: "myPhotoshopFile.psd" or "Red_car.jpg" for example.
4. When working in Photoshop, NEVER trash your unflattened files - Save both your print/web-ready and photoshop files. If you need to edit the image for any reason, you definitely want the photoshop file with all your layers.
BASICS OF DIGITAL IMAGE FILES
Resolution
The pixel dimensions (image size or height and width) of a bitmap image is a measure of the number of pixels along an image's width and height. Resolution is the fineness of detail in a bitmap image and is measured in pixels per inch (ppi) or another unit of measurement (cm, mm, etc). The more pixels per inch, the greater the resolution. Generally, an image with a higher resolution produces a better printed image quality.
Remember though that screen resolution is always low (usually 72ppi), so high resolution images on monitors are reflected by their scale - you can zoom in on a high res digital image, retaining more detail that a low res one.
This is different, but related to print quality, measured in dots-per-inch (dpi) which is controlled by the printer.
File Types
PSD: Photoshop format (PSD) is the default file format and the only format, besides the Large Document Format (PSB), that supports most Photoshop features. Because of the tight integration between Adobe products, other Adobe applications, such as Adobe Illustrator, Adobe InDesign, Adobe Premiere, Adobe After Effects, and Adobe GoLive, can directly import PSD files and preserve many Photoshop features. For more information, see Help for the specific Adobe applications.
When saving a PSD, you can set a preference to maximize file compatibility. This saves a composite version of a layered image in the file so it can be read by other applications, including previous versions of Photoshop. It also maintains the appearance of blended layers in the future.
16-bits-per-channel and high dynamic range 32-bits-per-channel images can be saved as PSD files.
JPG: JPG (Joint Photographic Experts Group) is what is called a "lossy" format, as it is based on a compression schema that decreases file size by "recording" only certain information about the image. Lossy means that the image looses quality each time it is saved and compressed. JPGs are 24-bit color files. JPGs are most useful for photographic images used on the web.
PNG: Portable Network Graphic is a lossless form of image compression - much like a GIF. PNGs save only the color information necessary (or selected) for the image quality in question. This form of compression is called "indexed color" - meaning exact color information is "recorded" in the file, so it reproduced exactly each time it is saved/copied. PNGs can save alpha transparency in 32-bit mode (unlike GIFs). Both PNGs and GIFs are most useful for graphics and images with large areas of solid colors on the web.
GIF: Graphics Interchange Format (sometimes called CompuServe GIF, after the company that developed it in 1987). It only supports up to 8 bits per RGB channel (thus 256 colors total) and is a lossless format. It is primarily good for solid and limited color range images. It can also save limited info for animations.
TIFF: Tagged-Image File Format (TIFF, TIF) is used to exchange files between applications and computer platforms. TIFF is a flexible bitmap image format supported by virtually all paint, image-editing, and page-layout applications. Also, virtually all desktop scanners can produce TIFF images. TIFF documents have a maximum file size of 4 GB. Photoshop CS and later supports large documents saved in TIFF format. However, most other applications and older versions of Photoshop do not support documents with file sizes greater than 2 GB.
TIFF format supports CMYK, RGB, Lab, Indexed Color, and Grayscale images with alpha channels and Bitmap mode images without alpha channels. Photoshop can save layers in a TIFF file; however, if you open the file in another application, only the flattened image is visible. Photoshop can also save annotations, transparency, and multiresolution pyramid data in TIFF format.
In Photoshop, TIFF image files have a bit depth of 8, 16, or 32 bits per channel. You can save high dynamic range images as 32-bits-per-channel TIFF files.
About Compression
Graphics file formats differ in the way they represent image data (as pixels or vectors), in compression techniques, and which Photoshop features they support. With a few exceptions (for instance Large Document Format (PSB), Photoshop Raw, and TIFF), most file formats cannot support documents larger than 2 GB.
Note: If a supported file format does not appear in the appropriate dialog box or submenu, you may need to install the format’s plug-in module.
About file compression
Many file formats use compression to reduce the file size of bitmap images. Lossless techniques compress the file without removing image detail or color information; lossy techniques remove detail. The following are commonly used compression techniques:
RLE (Run Length Encoding)
Lossless compression; supported by some common Windows file formats.
LZW (Lemple-Zif-Welch)
Lossless compression; supported by TIFF, PDF, GIF, and PostScript language file formats. Most useful for images with large areas of single color.
JPEG (Joint Photographic Experts Group)
Lossy compression; supported by JPEG, TIFF, PDF, and PostScript language file formats. Recommended for continuous-tone images, such as photographs. JPEG uses lossy compression. To specify image quality, choose an option from the Quality menu, drag the Quality pop-up slider, or enter a value between 0 and 12 in the Quality text box. For the best printed results, choose maximum-quality compression. JPEG files can be printed only on Level 2 (or later) PostScript printers and may not separate into individual plates.
CCITT
A family of lossless compression techniques for black-and-white images, supported by the PDF and PostScript language file formats. (CCITT is an abbreviation for the French spelling of International Telegraph and Telekeyed Consultive Committee.)
ZIP
Lossless compression; supported by PDF and TIFF file formats. Like LZW, ZIP compression is most effective for images that contain large areas of single color.
Digital Color
Bit depth specifies how much color information is available for each pixel in an image. The more bits of information per pixel, the more available colors and more accurate color representation. For example, an image with a bit depth of 1 has pixels with two possible values: black and white. An image with a bit depth of 8 has 28, or 256, possible values. Grayscale mode images with a bit depth of 8 have 256 possible gray values.
RGB images are made of three color channels. An 8-bit per pixel RGB image has 256 possible values for each channel which means it has over 16 million possible color values. RGB images with 8-bits per channel (bpc) are sometimes called 24-bit images (8 bits x 3 channels = 24 bits of data for each pixel).
In addition to 8-bpc images, Photoshop can also work with images that contain 16-bpc or 32-bpc. Images with 32-bpc are also known as high dynamic range (HDR) images.
See an example of differences and chart.
Bitmap Vs. vector graphics: A bitmap file contains information about each pixel that makes up the image - which means that increasing the scale of an image decreases its resolution and increases the amount of memory used. Photographic forms of images are bitmaps.
Vector graphics are created through mathematical formulas that determine line size, radius of arcs and color. Vectors can be reduced and enlarged without resolution degradation or proportion changes. Illustrator and InDesign are examples of print based vector apps. Flash uses vectors on the web.
The web is an RGB environment, low resolution (72 ppi), so any images you download are probably low res and RGB.