What does 300dpi mean for photographic works?

DPI (short for dots per inch): printing resolution (the number of dots that can be printed per inch, that is, printing accuracy). The DPI of a picture refers to the number of pixels per inch, which is similar to the density, that is, the number of pixels per inch of a picture, to indicate the clarity of the picture. The smaller the dpi value, the lower the definition. The definition of a photographic work reaching 300dpi is already very high, and it is an ultra-clear picture.

The relationship among the print size, the number of pixels of the image and the print resolution can be expressed by the following calculation formula:

Horizontal (vertical) pixel number of image = horizontal (vertical) resolution of printing × horizontal (vertical) size of printing,

Horizontal (vertical) pixel number of image/horizontal (vertical) resolution of printing = horizontal (vertical) size of printing.

For a specific image, the number of pixels in the image is fixed, so the printing resolution is inversely proportional to the printing size.

For example, if you want to print a 4 * 3-inch photo with a horizontal and vertical printing resolution of 300dpi, the number of pixels collected by the camera should be at least (300*4)*(300*3)= 1080000 pixels, about one million pixels. If the number of pixels collected is too low, the printing quality of the image will be reduced; if it is too high, the printing quality will not be improved.

The 300dpi of photographic works is the quality and size of the photos provided by the organizers clearly required by the photographic contestants to meet the printing clarity of this standard. Or a clear nominal work, so that visitors can clearly know the clarity level of the work in advance.

(Note: 300dpi is the limit of the printer. Pictures larger than 300dpi will not improve the clarity of the photos. Actually, 250 is enough. Even if a picture file larger than 300dpi is input into the printer, the printer will calculate the picture as 300dpi before printing. In addition, don't underestimate the printer's 300dpi. The photo quality of a 300dpi printer is unmatched by any printing equipment. )