2. Chapter Two Objectives
Understand “contrast”
Understand dynamic range to contrast
Understand tone distribution to contrast
Learn to manipulate end points and pivot points of gradation curve

3. Activity Go to Google Photos Open contrast.jpg
Improve the picture using Light options only (e.g. Exposure, Contrast)
Don’t press DONE; select SAVE COPY to create your own copy.

4. Overview
The human visual system is not an accurate color measurement device
It is a rather discriminating color comparative system

5. Contrast is the first aspect of difference we notice
How much difference is there between the lightest and darkest areas?

6. What’s the difference?

7. How is contrast controlled?
Dynamic range
Tone distribution

8. Dynamic Range End Points Highlight
Difference between an image’s lightest and darkest points
Referred to as Highlight and Shadow
The red ring in the cloud represents the image’s lightest point. The light ring in the grain elevator shadow is the image’s dark point. Every other pixel in the image falls between these two points.
Shadow

9. In Photoshop and the GIMP
End Points are discovered and set using Threshold and Levels features
Whether scanning existing slides, prints or art or color correcting digital photos, one always begins by setting proper highlight and shadow settings. Nothing else should be done to an image until these end points are set.

10. Activity Go to Google Photos Download face2.jpg
Open the picture in Photoshop
Duplicate the picture in Layers; name the new layer as “Highlight”
Image -> Adjustment -> Threshold
Move slider to isolate reflections on face
Change Blending mode to Screen for layer
Image -> Adjustment -> Invert
Change Blending mode to Darken/Multiply; adjust opacity

11. Tone Distribution(Curves)
Transition of tonal values between End Points
Tonal control points
Midtone
Quartertone
Three-quartertone

12. These images have identical Dynamic Range but not contrast
The difference is in each image’s tone distribution.

13. Activity Go to Google Photos Download 3 tonal pictures
Open the pictures in Photoshop; arrange them on screen (Windows->Arrange->3-up Vertical)
Convert tonal2 to tonal 3
Adjustments (palette) -> Curves
Convert tonal2 to tonal 1
Disable the last adjustment (close the eye icon)