Advanced Digital Image Enhancement Method
© Bob DiNatale
Activity: Curves...
Reading: Chapter 8 "Color Correction" - Studio Techniques by Ben Wilmore
Lesson 1: Using curves to color balance an image.
File Needed: [TheCar.TIF]
(If viewing from the Internet, click on photo on right)
1. Open "TheCar.TIF" file and optimize the image: Menu:>Image>Adjust>Levels
2. Select the "Color Sample" tool. Double click the tool and set the "Sample Size" to "5x5 Average".
3. Place 3 cross-hairs on the photo: #1 on a dark gray; #2 on a mid-
gray and #3 on a light gray
4. Notate values for
cross-hair #1 and determine a "target" number:
 

a) if 3 values are random use the average as the "target" number
b) if 2 numbers are close, average those 2 and use as the "target" number
{see table below}

5. Repeat step 4 for cross-hairs #2 & #3
6. From the menu select curves and color balance RGB value for neutral (page 200 Ben's Book)
  Menu:>Image>Adjust>Curves
- select the "Red" curve and click on the curve to add a point
-click the leftmost point
(dark) and enter the low red value for "input" and fir "output" enter the value determined in step 4 above.
-click the middle point and enter the mid red value for "input" and "output"
-click the right most point
(light) and enter the high red value for "input" and "output"
{repeat for the "Green" and "Blue" curves}
7. Select the license plate and copy to new layer.
8. Place another picker on the white area of the plate
9.
From the menu select curves and color balance RGB value for neutral.

{Hint: picking a lighter value to balance RGB curves will brighten the license plate}

Revision 1.0

Determining a "Target" Number
Cross-hair
Brightness
R
G
B
Avg.
#1
#2
#3
D
M
L
29
154
186
31
148
184
27
152
172
29
153
185

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