Print Resolution Explained
Digital Scaling & Resolution
Resolution is the measurement of the output quality of an image, usually in terms of pixels, dots, or lines per inch. A digital image is made up of many small squares of color called Pixels (short for Picture Element). The number of pixels across the width and height of the image is called resolution. An image with 640 pixels wide and 480 pixels high has a resolution of 640 x 480. The more pixels in the image file, the higher the resolution.
When it’s time to print, specify what resolution you want to print the image. Pixus uses the most advanced equipment available to produce vibrant graphics from digital files. In order to produce a “Photo Quality” print, 100 ppi (pixels per inch) must be used. Smaller resolution files can be printed, but less than optimum results will be achieved.
How do you determine whether the Size and PPI of your photo are adequate for a large graphic reproduction?
Determine the desired resolution before taking or purchasing a photo and consider the final output. Pixus needs 100 DPI (Dots Per Inch) to get a photo quality print. View the example on the right. You are designing a 22″ x 28″ poster and you want your image to be 22″ wide. The photograph you’re using is 5.5″ x 7″.
First enlarge the photo 400% to have a large enough background and check the resolution by opening your original photo in Photoshop or another photo program. Many programs offer different approaches to resolution, so it’s important to refer to your user manual for specific instructions. In PhotoShop, go to Image>file size (figure 1) and the size and resolution or pixels per inch will be displayed. If your photo is 400 ppi or larger, it’s ready to be enlarged and used as the background. Next, rescan the original or retake the digital photo at this larger size if the photo is less than 400 ppi.
Example: Original photo size is 5.5″ x 7″ at 72 ppi. Required photo size is 22″ x 28″ at 100 ppi.
5.5″ x 7″ enlarged by 4 equals a 22″ x 28″ which is a standard sized poster. The photo should now be enlarged 400% and have 400 ppi to allow enlargement of the photo without losing resolution. Since the original is only 72 ppi, these calculations tell us a higher resolution photo should be used as the background.
Tip: Once the artwork becomes electronic, it cannot be enlarged without the loss of quality. For the best quality image prints, begin with a higher resolution photograph when designing your project. Your image can always be resized when the project is finalized.
Resolution: Sample Images
Notice the PPI when looking at these examples. When the PPI is decreased, the quality of the photo is decreased in the image’s edges and overall clarity.
Vector vs. Raster
Have you ever wondered about the difference between bitmaps and vector graphics? Bitmaps, also known as raster images, are pixels in a grid. Each pixel contains tiny dots of color and when combined, make up the picture you see on your screen. Vector graphics are composed of scalable objects such as lines and curves. These are defined mathematically to ensure a high quality result no matter the amount of scaling. (Scaling is the enlarging or reducing of size.) Vector graphics are easily modified and are not affected by scaling. Vector graphics are commonly created in Adobe Illustrator and converting vector graphics to raster images is quite simple.
Raster images are produced with the use of digital image capture devices such as, digital scanners, digital cameras or pixel editing programs like Adobe Photoshop. Raster images are comprised of grids in digital picture elements and better known as pixels. Pixels are described as squares or rectangular shapes in black, white, gray or color. Converting raster files to vector can be difficult and often not possible due to the impact of scaling.
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