IMAGE DIMENSION - PRINT SIZE & QUALITY

The concept that the higher the printer resolution number, pixels per inch (PPI) or the file size in megabytes (MB), the better a print will look is not necessarily always true. Final print quality or what makes a good print also involves many other factors such as: how the image was captured (camera & lens quality), the file type (e.g. raw/jpeg), processing (colour space or colour profile), the printer, printheads, printer drivers, inks, media (photo paper versus canvass) etc. and even includes taking into consideration viewing distance (the capacity of the human eye to distinguish detail). 

All image dimensions on this website are provided in pixels and with a potential print size measurement using a high-resolution of 300 pixels per inch (ppi).  However, a good quality print could have a resolution anywhere from 180 ppi to greater than 300 ppi, depending on the distance from which the image is intended to be viewed.  Therefore, digital images may be developed at differing resolutions and sizes.

As general rule, prints that are meant to be viewed close-up should have resolution between 240 ppi -300 ppi.  For larger images, to be viewed from a distance further away, a lower ppi of 180 ppi to 240 ppi may be acceptable. 

For example, a 24MP image printed at a resolution of 300 ppi will allow a maximum print size of 20 x 13.3 inches which has a comfortable viewing distance of ~3 feet (generally considered to be 1.5 times the diagonal measurement of the image):

(6000 pixels/300 ppi = 20 inches) by (4000 pixels/300 ppi =13.3 inches)

However, by reducing the resolution to 200 ppi, the print size may be increased to 30 × 20 inches, with a comfortable viewing distance of ~4.5 feet.

(6000 pixels/200 ppi= 30 inches) by 4000 pixels/200 ppi = 20 inches)

Both prints should be of good to excellent quality for viewing.  A caveat to this, is that individuals who enjoy a photo may often want to take a closer look, thus one may wish to retain a higher resolution where possible from a practical versus technical perspective.

Note: The aspect ratio of a digital image cannot be changed without choosing to crop out portions of an image.

To determine an acceptable print size, consider where the image will be display, then consider the viewing distance, and decide on an appropriate resolution.

Once you have a sense of the resolution required you can use the formula below to determine a potential print size (inches).   

# of Pixels (long edge)/Resolution -Pixels per inch

By

# of Pixel (Short Edge) / Resolution - Pixel Per Inch

Using a good quality print lab is important. Most good quality print labs will provide guidance on the maximum size print(s) one can get from a digital image if they know the image’s specifications.