Photoshop Elements > Levels >
Eyedropper Calibration
There are three eyedroppers in the Levels adjustment panel.
You can use them to adjust Levels and to correct color.
Go to the
Other Levels Methods.
The default pixel values for the black-point eyedropper and the
white-point eyedropper are below.
| Black Point |
0 |
0 |
0 |
| White Point |
255 |
255 |
255 |
When you click on a black area with the black-point eyedropper,
you're "telling" Photoshop Elements that the area is black: 0,0,0.
Likewise, when you click on a white area with the white-point
eyedropper, you're "telling" Photoshop Elements that the area is
white: 255,255,255.
You may have encountered articles suggesting that you recalibrate
the eyedroppers to different values.
The suggested values vary.
The values below are common.
| Black Point |
20 |
20 |
20 |
| White Point |
240 |
240 |
240 |
If you recalibrate your eyedroppers to the above values, the
range of the pixel values from 0 to 255 will be compressed to a
range between 20 to 240.
This compression via the eyedroppers is the same as adjusting
the Output Levels sliders at the bottom of the Levels adjustment
panel.
The compression is described
below.
Should You Recalibrate?
Which values should you use, the default values or other values?
For most Photoshop Elements users, the default values are preferred.
Use other values only if your printer can't reproduce the entire
range of pixel values.
Test the Values
Do the following to test whether your prints will benefit from
compression of the pixel values.
1) Open a photograph.
2) Go to File > Duplicate.
You now have the original and a copy of the original.
3) Use the default eyedropper values to adjust the Levels of
the original.
4) Change the values of the black-point eyedropper and the white-point
eyedropper, as described below.
5) Use the new eyedropper values to adjust the Levels of the
copy.
Click the same areas that you clicked above.
6) Make prints of the original and the copy.
7) Compare the prints.
Use the values which render a better print.
When you use other values for the black-point eyedropper and
click on a black area in your photograph, the blacks become slightly
less black.
The difference in the two blacks below may not be evident on
your monitor.
Black (0,0,0)
Gray-Black (20,20,20)
Likewise, when you use other values for the white-point eyedropper
and click on a white area in your photograph, the whites become
slightly less black.
White (255,255,255)
Gray-White (240,240,240)
The change is about 7.8% less black or white, if you use the
values below.
| Black Point |
20 |
20 |
20 |
| White Point |
240 |
240 |
240 |
Using the new values will also change the other colors with values
between 0 and 20, and between 240 and 255.
For example, when you click on a black area in your photograph,
a red area (255,0,0) will also change.
The red will become less saturated (less vivid).
Red (255,0,0)
Gray-Red (235,0,0)
Do the following to recalibrate the black and white eyedroppers
to other values.
1) Double click the black-point eyedropper, the first eyedropper,
in the Levels adjustment panel.
The Color Picker window appears.
2) Enter 20 in each of the the RGB value boxes or enter 141414
in the # box.
3) Click OK.
4) Double click the white-point eyedropper, the third eyedropper,
in the Levels adjustment panel.
The Color Picker window appears.
5) Enter 240 in each of the RGB value boxes or enter F0F0F0 (zeros)
in the # box.
6) Click OK.
How Were the Above
Values Determined?
The above values are often used when printing on a half-tone
press, such as a brochure.
When an ink drop hits the paper in a half-tone printing press,
the ink spreads on the paper.
An ink drop on newsprint will spread a lot.
This is called high dot gain.
On the other hand, on coated paper, the ink drop will spread
far less.
This is called low dot gain.
To reduce the spreading, less black ink is used by lowering the
dot gain to 92% or a similar amount.
255 - (.92 x 255) = 20
The black point should be set to 20,20,20.
100% white is not used so white areas on the photograph are darker
than the white of the paper.
A common white point value is 6%.
255 - (.06 x 255) = 240
The white point should be set to 240,240,240.
