Correcting Tone and Exposure - Beginning Photo Retouching and Restoration Using GIMP - page 55

Figure 3-21. Creating layers for use in finding black and white points

3. Activate the White Point layer, then open the Threshold dialog box (Image Menu

➤ Colors ➤ Threshold). Move the black slider to the far right, and then proceed
to slowly move it toward the left, until the brightest cluster of pixels begins to
emerge (Figure 3-22 ).

Figure 3-22. Finding the white point of the image

4.

Now activate the Black Point layer, and open the Threshold dialog again. Move
the black slider to the far left, then slowly toward the right, until the darkest
cluster of pixels begins to emerge (Figure 3-23 ).