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

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.

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

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

What’s the difference?

How is contrast controlled? Dynamic range Tone distribution

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

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.

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

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

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

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)