Below, the red numbers are the number of stops in a photograph file.

The blue numbers are the quantity of brightness levels.

1	2	3	4	5	6
Shadows		Midtones			Highlights
64	128	256	512	1024	2048

That's great if you have lots of editing to do in the highlights.

There are 3,072 brightness levels (1024 + 2048).

However, most photographs are more about the midtones.

There are only 768 brightness levels in the midtones (256 + 512).

And, photographers often have to lighten deep shadow areas.

There's not much for you to lighten.

There are only 64 brightness levels in the deepest shadows.

Why?

Why are most of the brightness levels placed in the highlight areas?

You can skip the answer, if you wish.

The answer involves sweeping the cobwebs off of some 6th-grade math.

We use a base 10 numbering system (dec), and computers use a base 2 numbering system (bin).

Both of these numbering systems are place-value systems.

A number is determined by the value of number and its place.

For example, let's look the number 5,555.

The five in the right-hand column below means 5 x 1.

In the next column, to the left, the 5 means 5 x 10.

In the next column, five means five x 100.

Finally, in the last column to the far left, the 5 means five x 1000.

1000s	100s	10s	1s
5	5	5	5

What's the base ten numbering system?

In a base ten number system, each column is 10x greater than the one to the right.

Each column can have any of ten numbers, 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.

1000s	100s	10s	1s
0 - 9	0 - 9	0 - 9	0 - 9

Let's say we have 4,096 brightness levels in a photograph of a tiger.

Here's 4,096 in base ten.

1000s	100s	10s	1s
4	0	9	6

Digital photography uses the base two numbering system.

In a base 2 numbering system, each column is 2x greater than the one to the right.

Each column can have only one of two numbers, 0 or 1.

4,096, the number of brightness levels in our tiger photograph, is 1000000000000 in base two.

Here's how 4,096dec turns into 1000000000000bin.

1	0	0	0	0	0	0	0	0	0	0	0	0
4096	2048	1024	512	256	128	64	32	16	8	4	2	1

(Here's the easy way to do the math: Base Conversion Calculator.)

Now, unfortunately, the photography world switches the order of the number columns.

In the above charts, the highlights are on the left.

In photography, the convention is the opposite.

The highlights are on the right.

So, switch your brain around.

Here's how the 4,096 brightness levels of our tiger photograph are distributed across the columns in the photography world.

1	2	3	4	5	6
Shadows		Midtones			Highlights
64	128	256	512	1024	2048

75 percent of the brightness levels are in the last two columns—the highlights.

Now you know why—it's the base two numbering system.

There are only 64 brightness levels in the darkest part of the scene.

That's only about two percent of the total number of brightness levels.

That's not so bad, compared to a JPEG file.

A JPEG file only has 4 levels of brightness in the shadows.

Here's how the 255 brightness levels of a single channel are distributed.

1	2	3	4	5	6
Shadows		Midtones			Highlights
4	8	16	32	67	128

Having only 4 levels of brightness becomes a problem if you're going to edit a shadow area.

Posterization, or banding, an abrupt change in color or brightness level, may occur.

Gamma processing does alleviate the lack of brightness levels in shadows somewhat.

Gamma processing rearranges the brightness levels to better correspond to human vision.

They're distributed "downward."

So, instead of having 4, there are 10 brightness levels in the shadows.

Still, it's better to have the 64 brightness levels in a raw file, to edit, rather than only 10 in a gamma-processed JPEG file.

If your photograph is going to require editing of shadow areas, save it as a raw file.

A further refinement is to Expose to the Right.

Go the Gamma Explained.

Let's look at more advantages.

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