Often clients ask me “what is 300dpi?”
I’ve had to explain this to them on numerous occasions. However I felt it was better to place a better explanation on here. WiseGeek explains this far better than I can. So here it is:
DPI (dots per inch) is a measurement of printer resolution, though it is commonly applied, somewhat inappropriately, to monitors, scanners and even digital cameras.
For printers, the DPIDPIDPI specification indicates the number of dots per inch that the printer is capable of achieving to form text or graphics on the printed page. The higher the DPIDPIDPI, the more refined the text or image will appear. To save ink, a low DPIDPIDPI is often used for draft copies or routine paperwork. This setting might be 300 or even 150 DPIDPIDPI. High resolution starts at 600 DPIDPIDPI for standard printers, and can far exceed that for color printers designed for turning out digital photography or other high-resolution images.
In the case of monitors, DPIDPIDPI refers to the number of pixels present per inch of display screen. The technically correct term is “PPI” or pixels per inch, but DPIDPIDPI is commonly used instead. A display setting of 1280 x 1024 has 1.3 million DPIDPIDPI, while a setting of 800 x 600 has 480,000, or less than half the resolution of the higher setting. With fewer dots per inch, the picture will not have the clarity that can be achieved with a higher DPIDPIDPI saturation. This is because displays create images by using pixels. Each dot or pixel reflects a certain color and brightness. The greater the DPIDPIDPI, the more detailed the picture can be. Higher DPIDPIDPI also requires more memory and can take longer to ‘paint’ images, depending on the system’s video card, processor and other components.
Scanners also operate at different resolutions. Scan time will increase with higher DPIDPIDPI settings, as the scanner must collect and store more data. However, the greater the DPIDPIDPI, or requested resolution, the richer the resulting image. A high DPIDPIDPI setting mimics the original image in a truer fashion than lower DPIDPIDPI settings are capable of doing. If the image is to be enlarged, a high DPIDPIDPI setting is necessary. Otherwise the enlarged picture will look “blocky” or blurry because the software lacks information to fill in the extra space when the image is enlarged. Instead it “blows up” each pixel to “smear” it over a wider area. Technically again, the more correct term in this application is sampled PPI, but DPIDPIDPI is more often used.
Digital cameras have their own specifications in terms of megapixels and resolution, but DPIDPIDPI is often mentioned in this context as well. Since DPIDPIDPI in all cases refers to the output image, a digital camera capable of the most basic current standards of resolution —- 3.0 megapixels and better —- will output an image capable of taking advantage of a very high DPIDPIDPI setting on the printer. However, if your printer is only capable of 600 DPIDPIDPI, the extra resolution of the camera will be lost in the printing process. When buying or upgrading components it is therefore critical that each product is capable of supporting the highest standards of any interfacing product.
Tags: dots per inch, dpi, resolution
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