Image Capture Method

SCANNING

In computing, an image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop (or flatbed) scanner where the document is placed on a glass window for scanning. Hand-held scanners, where the device is moved by hand, have evolved from text scanning “wands” to 3D scanners used for industrial design, reverse engineering, test and measurement, gaming and other applications. Mechanically driven scanners that move the document are typically used for large-format documents, where a flatbed design would be impractical. Modern scanners typically use a charge-coupled device (CCD) or a Contact Image Sensor (CIS) as the image sensor, where as older drum scanners use a photomultiplier tube as the image sensor. A rotary scanner, used for high-speed document scanning, is another type of drum scanner, using a CCD array instead of a photomultiplier. Other types of scanners are planetary scanners, which take photographs of books and documents, and 3D scanners, for producing three-dimensional models of objects.  Another category of scanner is digital camera scanners, which are based on the concept of reprographic cameras. Due to increasing resolution and new features such as anti-shake, digital cameras have become an attractive alternative to regular scanners. While still having disadvantages compared to traditional scanners (such as distortion, reflections, shadows, low contrast), digital cameras offer advantages such as speed, portability and gentle digitizing of thick documents without damaging the book spine.

SCREENGRABS

MICROSOFT WINDOWS:
Prnt Scrn captures a screenshot of the entire desktop
Alt + Prnt Scrn captures only the active window or active dialog box
MAC OS X:
Cmd + Shift + 3 captures a screenshot of the entire screen and save it to desktop
Cmd + Shift + 4 captures chosen area of the screen and save it to desktop

DIGITAL CAMERA

A digital camera (or digicam) is a camera that takes video or still photographs by recording images on an electronic image sensor. Most cameras sold today are digital, and digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones) to vehicles. Digital cameras are made in a wide range of sizes, prices and capabilities. The majority are camera phones, operated as a mobile application through the cellphone menu. Professional photographers and many amateurs use larger, more expensive digital single-lens reflex cameras (DSLR) for their greater versatility. Between these extremes lie digital compact cameras and bridge digital cameras that “bridge” the gap between amateur and professional cameras.

Image Formats

JPEG

(Joint Photographic Experts Group) is a compressed image file format. not limited to a certain amount of colour, like GIF images are. Therefore, the JPEG format is best for compressing photographic images.So if you see a large, colourful image on the Web, it is most likely a JPEG file. While JPEG images can contain colourful, high-resolution image data, it is a lossy format, which means some quality is lost when the image is compressed. If the image is compressed too much, the graphics become noticeably “blocky” and some of the detail is lost. Like GIFs, JPEGs are cross-platform, meaning the same file will look the same on both a Mac and PC.

GIFF

The letters “GIF” actually stand for “Graphics Interchange Format,” but you don’t need to remember that. What you should know is that a GIF is a compressed image file format. GIF images use a compression formula originally developed by CompuServe (which is why you see the term “CompuServe GIF” in Photoshop, for those of you that care). GIFs are based on indexed colours  which is a palette of at most 256 colours. This helps greatly reduce their file size. These compressed image files can be quickly transmitted over a network or the Internet, which is why you often see them on Web pages. GIF files are great for small icons and animated images, but they lack the colour range to be used for high-quality photos.

TIFF

Stands for “Tagged Image File Format.” It is graphics file format created in the 1980’s to be the standard image format across multiple computer platforms. The TIFF format can handle colour depths ranging from 1-bit to 24-bit. Since the original TIFF standard was introduced, people have been making many small improvements to the format, so there are now around 50 variations of the TIFF format. So much for a universal format. Recently, JPEG has become the most popular universal format, because of its small file size and Internet compatibility.

PICT

Image file saved in the Macintosh PICT format; may contain both vector and bitmap data and can use thousands of colours; also supports RLE (Run-length encoding) and JPEG compression to reduce the file size. PICT files often use the .PCT file extension, especially on the Windows platform.

BMP

Uncompressed raster image comprised of a rectangular grid of pixels; contains a file header (bitmap identifier, file size, width, height, colour options, and bitmap data starting point) and bitmap pixels, each with a different colour. BMP files may contain different levels of colour depths per pixel, depending on the number of bits per pixel specified in the file header. They may also be stored using a greyscale colour scheme.

PNG

Image file stored in the Portable Network Graphic (PNG) format; contains a bitmap of indexed colours and uses lossless compression, similar to a .GIF file but without copyright limitations; commonly used to store graphics for Web images. The PNG format was created in response to limitations with the GIF format, primarily to increase colour support and to provide an image format without a patent license. Additionally, while GIF images only support fully opaque or fully transparent pixels, PNG images may include an 8-bit transparency channel, which allows the image colours to fade from opaque to transparent. PNG images cannot be animated like GIF images. However, the related .MNG format can be animated. PNG images do not provide CMYK color support because they are not intended for use with professional graphics. PNG images are now supported by most Web browsers. Mac OS X 10.4 and later saves screenshots as PNG files. Ubuntu Linux also stores print screen screenshots in the PNG format.

EPS

Encapsulated PostScript File. PostScript (.PS) file that may contain 2D vector graphics, bitmap images, and text; may also include an embedded preview image in bitmap format; can be placed within another PostScript document. EPS files are supported by several different drawing programs and vector graphic editing applications. They are often used as a standard means for transferring image data between different operating systems.

Problems Associated with Image Capture

MOIRE PATTERNS

A moire pattern will occur in the printing process when two, or more, repeating patterns overlap each other. Similar to the effect on television when a presenter wears a criss-cross pattern on their suit, this effect will result in halftone areas of the print if the line screens of two different inks have been output at the same angle. Therefore, it is important that the screen angles of each printing plate are different. Moire patterns can also occur when a halftone image is scanned and printed, as the dot pattern from the printed halftone can clash with the new line screen. There are numerous ways to reduce this, from blurring the scan slightly, to reducing the size of the scan, to various Photoshop techniques and filters.

PIXELATION

Pixelation happens when the individual pixels in a digital photograph are visible. Pixels are blocks of colour that make up the photograph. Pixelation only applies to the use of digital cameras, not regular cameras. In order to see the pixels, you can zoom in very close on a photograph.

RESOLUTION

Resolution is the term used to describe the number of dots, or pixels, used to display an image. Higher resolution means more image detail.

COLOUR CASTS

A colour cast is an unwanted tint in the image due to the lighting, the white balance of the video camera, or the type of film stock used given the lighting conditions during the shoot. Colour casts exist because one or more colour channels is inappropriately strong or weak. Furthermore, colour casts aren’t usually uniform across an entire image. Often, colour casts are stronger in one portion of the image (such as the highlights) and weaker or non existent in others (the shadows, for example).