When working with images, especially for print, it’s helpful to know about image resolution and DPI. Let us begin with the basics:
What is image resolution?
Resolution is the number of dots of ink or electronic pixels that make up an image, whether it’s in print or be viewed on the computer screen.
What is pixels and megapixels?
There are many ways to measure resolution. The most basic is the number of pixels the image consists of, which may be expressed in the number of megapixels. A picture of the 1 megapixel contains 1 million pixels, which refers to the number of columns (width) and rows (height) of the image, such as 1000 x 1000. An image of 2048 x 1536 has a total of 3,145,728 pixels, or 3.1 megapixels. The images in YAY have a resolution of respectively 0.3 megapixels (small), 3-megapixel (medium) and the original resolution of between 3.1 and 30 mega pixels (large).
What is DPI?
In addition to image resolution is expressed by showing the number of dots per inch. We got multiple units of measure based on what is appropriate (DPI, PPI, SPI, and LPI). The best known measure is the DPI (dots per inch) that says how many dots there are per inch. This expresses the resolution of a printer and should only be used in this context. It refers to the number of dots of ink or toner a printer can print a photo in. In general a higher number means a sharper image. DPI is unfortunately often used to express a scanner or a display resolution. It is misleading and should be avoided.
DPI, Resolution and Print size
When someone asks for “an image of 300 DPI” it is natural to believe that they want a picture with 300 pixels per printed inch, but if the print size is not given, this makes little sense. To better specify the desired resolution you should also state the size of the print – and make sure that the printer supports such a resolution. If the printer does not support more than 100 DPI, there is no reason to use a picture with higher resolution.
In conclusion we can say that a digital image does not have a specific number of DPI. An image of 1000 x 1000 pixels can be printed on 4 x 4 inches with a resolution of 250 DPI, or 10 x 10 inches at 100 DPI. Please also be aware that good imaging software easily allows you to change the DPI without compromising picture quality (just remember to avoid “resample image”, as it leads to loss of quality).