The number represents the size of the pixel. Of course, the more, the better. Take a look below and you will understand. "Pixel" is composed of the two words Picture (image) and Element (element). Letters are a unit used to calculate digital images. Just like photographic photos, digital images also have continuous shades of tones. If we enlarge the image several times, we will find that these continuous tones are actually composed of many It is composed of small square dots with similar colors. These small square dots are the smallest unit "pixel" that makes up the image. This is the smallest graphic unit that can be displayed on the screen, usually a single stained point. The higher the pixels are, the richer the color palette they have, and the more realistic the colors can be expressed. The English name of the effective number of pixels is Effective Pixels. Different from the maximum pixels, the effective number of pixels refers to the pixel value that actually participates in photosensitive imaging. The highest pixel value is the real pixel of the photosensitive device. This data usually includes the non-imaging part of the photosensitive device, and the effective pixel is the value converted at the zoom magnification of the lens. Taking Minolta's DiMAGE7 as an example, its CCD has 5.24 million pixels (5.24 Megapixels). Because part of the CCD does not participate in imaging, the effective pixels are only 4.9 million.
Digital pictures are generally stored in pixels, and each pixel is the smallest unit in a digital picture. The larger the pixels, the larger the image area. To increase the area of ??a picture, if no more light enters the photosensitive device, the only way is to increase the area of ??the pixels, which may affect the sharpness and clarity of the picture. Therefore, when the pixel area remains unchanged, the largest picture pixel a digital camera can obtain is the effective pixel.
When users buy digital cameras, they usually see merchants advertise "maximum pixels up to XXX" and "effective pixels up to XXX". So how should users choose? When choosing a digital camera, you should pay attention to the effective pixels of the digital camera. The number of effective pixels is the key to determining the quality of the picture.
DPI stands for resolution, which refers to the number of dots per inch. DPI can be subdivided into horizontal resolution and vertical resolution. For example, a 1 inch * 1 inch picture, if its horizontal resolution The resolution is 100 dpi and the vertical resolution is 50 dpi. That is to say, it is divided into 100 small segments per inch horizontally and 50 small segments per inch vertically, just like a grid on a meter stick. This picture has a total of 100 *50=5000 grids, this picture has 5000 pixels. Since its horizontal resolution and vertical resolution are not equal, each pixel is a tiny rectangle.
So the actual pixel It is a concept of area, and because the pictures produced by general computers/digital cameras have the same horizontal resolution and vertical resolution, each pixel is a tiny square, so it is called "DPI" which means the length per inch. "The number of pixels" is actually the "number of dots per inch of length".
The area size of each pixel is determined by the production process. The higher the process, the smaller the area of ??each pixel, and the smaller the area of ??each pixel per square inch of the screen. It can accommodate more pixels, the higher the dpi value, the finer the image. The pixels are so small that the human eye cannot distinguish them, and the image looks no different from the actual one.
This is how the concept of "how many megapixels" in a digital camera comes from. For example, a camera can take a photo of up to 1600 pixels * 1200 pixels. Its pixel value is 1600 * 1200 = 1.92 million, which is approximately equal to 2 million. This is a 2-megapixel digital camera.
So the 300 dpi mentioned in the question means that there are 300 dots per inch in the horizontal and vertical directions on the screen. This camera The actual height of the machine screen can be calculated by combining the number of pixels and dpi. For this machine, 400 pixels is 400/300=1.33 inches, and 533 pixels is 533/300=1.78 inches.
For a computer photo, you can change its resolution in Photoshop's "Image" - "Image Size" menu. The default is 72. If you change it to a smaller size, you will reduce the image. If you change it to a larger size, you will enlarge the image (the image quality will be lost). ), in fact, it is just the effect of zooming in and out. The real impact is on some image printout situations that require high resolution. You can open the "File" - "Print Options" menu to view the print preview.
(Attachment: 1 inch = 25.4 millimeters)