Threshold

Threshold determines whether an edge exists.

If You:	Then:
Enter 0	All of the pixels in the photograph will be sharpened.
Enter 10	Two adjacent pixels must be more than 10 brightness levels apart for sharpening to occur.
Enter 20	Two adjacent pixels must be more than 20 brightness levels apart for sharpening to occur.

Review & Typical Values

Here's a review of the above three settings, and values that are typically used for each setting.

	Amount	Radius	Threshold
What It Does	If the value ↑, sharpening ↑.	If the value ↑, sharpening ↑.	If the value ↑, sharpening ↓.
Typical Values	50% - 300%	.5 - 3	0 - 20

Setting the Values

100% & Most Important

• Always view your photograph at 100% magnification.

Photoshop uses dithering to smooth the transitions between pixel values at other magnifications.

This dithering can affect how the sharpening looks.

Double click the Zoom tool icon to go to 100% magnification.

• Evaluate the most important part of the photograph that has areas with both detail and little detail.

For example, if you're sharpening a portrait, evaluate the sharpening by looking at an eye and cheek.

Best Way to Judge - Look at the Output

The best way to judge sharpening is by looking at the output, be it monitor or print.

When printing ink-jet prints, you need to choose a sharpening level that's sharper than the level that looks good on your monitor.

Glossy papers will require less sharpening than matte papers.

Principle Determinant

Of Sharpening - Detail

The principal determinant of sharpening is the amount of detail in the photograph.

Photographs with lots of detail, such as an ancient Greek krater depicting athletics, often require more sharpening.

Photographs with little detail, such as a foggy moor, often need very little sharpening.

Detail & Frequency

You may encounter the term frequency for detail.

High frequency image information is detail.

Low frequency image information is little detail.

Photographs with

Both Detail & Little Detail

Of course, many photographs contain areas with detail and little detail.

These photographs may require selective sharpening.

With selective sharpening, you can "burn-and-dodge" with sharpening.

You can use more sharpening in parts of a photograph, and less in other areas.

Selective sharpening is described in the next section.

Radius First

In the Unsharp Mask window, Amount is first, followed by Radius and Threshold.

However, Radius is the most important value.

So set it first based on the amount of detail in your photograph.

Detail

Use a small radius for photographs with fine detail, such as .5 to 1.

Little Detail

Use a larger value for photographs with less detail, such as 2 to 3.

Here are some suggested values.

Subject	Radius
General	1
Subjects with expanses of tone & color	1
People (Use 1 for headshots)	2
Interiors, exteriors, & landscapes	.5
Out-of-focus photographs	4

Amount Starting Points

Detail

When using a small Radius value, use a higher Amount value, such as 200% and 300%.

Little Detail

When using a higher Radius value, use a lower Amount value, such as 50% and 100%.

Threshold Starting Points

Remember, a lower Threshold value increases its effect.

Detail

For photographs with detail, use a small value, such as 0 to 4.

The small value means all of the edges in your photograph will be sharpened.

Little Detail

For photographs with little detail, use a higher value, such as 8 to 12.

The higher value means not all of the edges in your photograph will be sharpened.

Summary

	Amount (%)	Radius (Pixels)	Threshold (Levels)
What It Does	If the value ↑, sharpening ↑.	If the value �����, sharpening ↑.	If the value ↑, sharpening ↓.
Typical Values	50% - 300%	.5 - 3	0 - 20
General	85	1	4
Subjects with expanses of tone & color	150	1	10
People	75	2 (Use 1 for headshots)	3
Interiors, exteriors, & landscapes	225	.5	0
Out-of-focus photographs	65	4	3

The next section discusses selective sharpening using Unsharp Mask Sharpening.

You can apply sharpening only to parts of a photograph.

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