William Liao

October 19, 2021

Just noticeable difference

In printing, resolution is described as dots per inch or DPI. 

For text documents, 150 DPI is usually good enough.  

For customer-facing documents like posters and brochures where image quality is a priority, it’s normal to double the DPI up to 300. 

In use cases where even higher resolution images are needed, the DPI doubles again to 600. 

Though it’s possible to go even higher to 1200 DPI and above, most people don’t bother for one simple reason: the increase in DPI stops being noticeable. 

There’s a concept in psychology called just noticeable difference, which describes the minimum amount of change that would need to occur for someone to detect a difference at least 50 percent of the time. 

Work that successfully crosses the just noticeable difference threshold is usually credited for moving the needle. Everything else is noise. 

For the same reason it doesn’t make any sense to go above 1200 DPI, there are things that don’t make a difference — enough of one at least — to justify the effort. 

If the change isn’t noticeable, did anything really change at all?