Construct 3 recompress images
But when displayed side by side on the same computer monitor-“painted” onto the screen using identically sized pixelsthe first image would look much larger than the second. Of course, the second digital image would still represent the original in its totality it would just be less fine-grained than the first, as if Seurat used a thicker brush to make his dots. With different settings on our scanner, we could digitize that same 3_ x 5_ photograph at 100 dpi and arrive at a much “smaller” image size of 300 x 500. Note that digitization disassociates an image from its real-world size. But if you wanted to examine the eyes of Dorothea Lange’s famous “Migrant Mother” more closely, the version scanned at a higher resolution would be a far better choice. For instance, 900 x 1,500 would be the image size of a 3_ x 5_ photograph scanned at 300 dots per inch (3 times 300 by 5 times 300).įigure 20: At a small size, both of these close-upsthe left scanned at 72 dpi and the right at 300 dpiwould look identical on a computer screen. Digital image size is expressed by two numbers, the width in dots times the height in dots (otherwise known as pixels on a computer screen). The breadth of the color palette is called the bit depth, ranging, as already noted, from 1 for simple black and white to 24 (or higher) for a virtually limitless palette of colors that Seurat and his Impressionist friends would have envied. Close up, a digital image looks as if the pointillist painter Georges Seurat decided to use graph paper instead of a blank canvas, carefully dabbing a single dot of color into each box of the grid. For images, as with scanned texts, the two key measures of digital sampling are bit depth and resolution.
In digitizing images, as with all digitizing, the quality of the digital image rests on the quality of the original, the digitizing method employed, the skill of the person doing the digitizing, and the degree to which the digital copy has adequately “sampled” the analog original. As with many of the more technical subjects we discuss in this book, image capture and management is a much larger and more complex topic than we can discuss in detail here, and those contemplating a major project will want to consult more specialized guides. In that case, you need to focus on a wide range of issues, ranging from fidelity to the original to long-term preservation.
#Construct 3 recompress images archive
At the other end of the spectrum, you might be creating an online archive of color lithographs from the early twentieth century.
In that case, you can do some quick scans from books on an inexpensive scanner the standard should be whether it is large and detailed enough to convey the information you want your students to see. You might, for example, be creating a website for your course and want a few images for purely illustrative purposes. Although the original yields a higher quality digital reproduction, it also often increases costs because large or fragile originals require complex, special handling.Īlso, as with text, the goals of your website, your intended audience, and your budget will shape your digitizing plan. In addition, you will often face the question of whether to work from an original or a surrogate like a slide. But some visual materialsslides, transparencies, large format documents like maps, or fine linear illustrations (such as engravings in the nineteenth-century press)require more specialized equipment, photographic expertise, or scanning techniques. You can digitize many images with the same inexpensive scanners or cameras as you might use with text. S with text, turning analog visual materials into digital objects can be as easy as operating a photocopier. Becoming Digital: Preparing Historical Materials for the Web Digital Images