Is pixel a dot ?

naseeam used Ask the Experts™
Following is a question from Image Signal Processing Book:

Determine the actual physical measurement in millimeters of an image with 1400 rectangular pixels and a resolution of 72 dpi.

Is pixel a dot ?
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Distinguished Expert 2018

Although commonly used as DPI(Dots Per Inch), what is typically meant when talking about resolution(like that of a screen) is PPI(Pixels Per Inch).

So for this specific question they probably mean PPI, instead of DPI, since the two are commonly used interchangeably.

Hopefully this will get you the info you need, but if not, please feel free to ask any follow up questions.

Devin Becker
Joe WinogradDeveloper
Fellow 2017
Most Valuable Expert 2018
Hi Naseeam,
The terms pixel and dot are often used interchangeably, but they're not really the same. I recommend doing some reading at Wayne Fulton's excellent site, A few scanning tips. In particular, here are some must-read sections:

Photographic Resolution - How much can we scan?
Pixels, Printers, Video - What's With That?
What is a digital image anyway?

Here are other helpful articles on the subject:

PPI vs. DPI: what’s the difference?
How do pixels and DPI and resolution and picture size and file size all relate?
The 72 PPI Web Resolution Myth
JPEG Myths and Facts

Regards, Joe


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