High & Low Resolution

High

If there are lots of pixels per inch, the resolution is high.

Prints are often made with a high resolution, such as 300 ppi.

On such a print, the pixels are tiny.

There are many of them squeezed into every inch.

Low

If there are few pixels per inch, the resolution is low.

A billboard may have a resolution of only six pixels per inch.

If you looked at the billboard from one foot away, you could see these enormous pixels.

But, because billboards are viewed from a distance, more pixels per inch are not needed.

A low resolution is sufficient.

Lots of Pixels Per Inch - Higher Resolution

Few Pixels Per Inch - Lower Resolution

Example

The small version of the picnic table photograph below is small because the resolution (300 ppi) "told" it to be small.

The photograph's pixels are closely spaced—300 ppi.

Similarly, the other version of the picnic table photograph is bigger because it's resolution (72 ppi) "told" it to be big.

The same pixels are now spaced out over a larger area—72 ppi.

Resolution

Preconceptions

There are two common preconceptions about resolution.

#1 Preconception

The pixel dimensions of a file are not size dimensions.

They're geometric dimensions.

A JPEG file from a 6 megapixel camera typically has these pixel dimensions:

3008 pixels x 2000 pixels

It looks like the file has a physical size, but it doesn't.

3008 x 2000 is just a description of how the pixels are arranged—their geometric pattern—not their size.

The file needs a resolution to "tell" the pixels how big they should be.

We'll get to that.

#2 Preconception

People often think that pixels have a fixed size.

Nope.

Pixels can change their size.

If we squish them into a small print, they get smaller.

If we spread them thinly on a huge print, they get bigger.

Pixels are very accommodating.

Summary

Physical Size = Pixel Dimensions / Resolution.

Let's look at another example.

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