Scanner resolution details - common terms (2)

4. Display resolution

There are two different representations of monitor resolution.

The first method is to describe the total amount of information a monitor can display at the same time. The common display resolutions of PCs are as follows: 640~480 (Pixel), 800~600 (Pixel) and 1024X768 (Pixel). The first number represents the number of horizontal pixels of the screen, and the second number represents the number of vertical pixels of the screen. For example, 640~480 (Pixel) means 640 pixels per line for a total of 480 lines. The higher the display resolution of the display, the greater the range of images that can be seen at a time when working. For professional designers who often deal with large-size, high-resolution images, it is best to use a display with a higher resolution, such as 1152X864 (Pixel) or 16001200 (Pixel).

The second method refers to the number of dots or lines described per inch on the screen. Different manufacturers and different types of monitors have different values. The computer monitor typically uses a resolution of 72 dpi per inch. But not all sizes of display are the same, it varies with the size and resolution of the display. You can also change the resolution of the current screen via the "Display Properties" dialog box, but the range is very limited.

The resolution of the display will only affect the convenience of the user when working and will not affect the output quality of the image data.

The size of the image on the screen depends on the image's pixel size, monitor size, and monitor resolution settings. The display size of the image on the screen is determined by the pixel size of the image plus the size and settings of the display. The file size of the image is proportional to its pixel size.

It should be noted that the resolution of the image displayed on the screen is very low. Although many images appear colorful and dazzling on the screen, the monitor is almost the lowest resolution of any digital image media. In use, the resolution of the display is almost always lower than the output resolution set for the image, so the image displayed on the screen is much larger than the printed image.

In Photoshop, image pixels are directly converted to display pixels, which means that when the image resolution is higher than the display resolution, the image is displayed on the screen larger than the specified print size. For example, when a 1 inch X1 inch, 144 dpi image is displayed on a 72 dpi display, it is displayed in a 2 inch by 2 inch area on the screen. Because the display can only display 72 pixels/inch, it takes 2 inches to display 144 pixels that make up one edge of the image.

5. Output resolution

The output resolution refers to the density information required for the final output of the image to a color printer or other digital printing device.

The output resolution is an important factor that affects the print quality. If the output resolution is lower than the printing device's requirements, the print image will lack gradation and the image will appear grainy. Conversely, if the output resolution is too high, unnecessary output time and costs will increase, and the finer levels of contrast may also be lost.

When the output device is a printer, the printer resolution limits the output resolution. Printer resolution refers to the dots per inch (dpi) that the printer can produce in both horizontal and vertical directions. The higher the resolution of the printer, the smaller the dots it produces, and the more continuous it appears in the hue of the printed image. The printer resolution limits the maximum number of single colors that can be represented in a print. For best results, use an image resolution that is proportional to (but not the same as) the resolution of the printer. If the laser printer's output resolution is 300dpi to 600dpi, it will print better on 72dpi to 150dpi images.

When the final output device is a continuous-tone printer, images close to the original may be reproduced as long as the output resolution is approximately equal to the printer resolution, such as sublimation printers and some hot-wax printers. The resolution of the printer itself is the deciding factor. Generally, it is considered that the output resolution is equal to the resolution of the printer. This results in a good effect. For example, using a 300 dpi sublimation printer with a 300 dpi output resolution will give good results. For an original image using a continuous-tone printer as the final output device, only the factors of enlargement factor and printer resolution need to be considered when calculating its scanning resolution, namely:

Scan resolution; magnification factor x printer resolution.

(to be continued)