Kenneth Morris Lee
Selective Contrast Curves in Photoshop

This article describes an improvement to the usual methods of adjusting contrast with Photoshop Curves. To avoid tedious selection of individual objects, we can add a Color Range Mask or a Blend If adjustment to a Curves correction.

To read a related article about toning monochrome images, see Selective Toning in Photoshop.
To read a related article about sharpening images, see Selective Sharpening in Photoshop.

Before Starting: Convert to 16-Bit

 For best results and to avoid banding, convert the image to 16 bit.

Color Range Mask

To darken only the flower petals with usual methods, we have to select them first by using selection tools which can be tedious and error-prone. Instead, let's select them by their brightness range.


Original grayscale image

Add a Curves adjustment layer. Do not adjust the curves yet.
And a luminosity mask to the Curves layer.
Click on the mask and choose Selection > Color Range...
Specify a high brightness value so that only the flower petals elements are selected.
Adjust the Fuzziness slider to avoid any abrupt transitions.


We have made a mask which selects only the flower petals. The leaves have been masked.

Edit the Curves adjustment layer to darken the selected values.

Here is the final image:


After Curves adjustment to the selected range
The leaves are unaffected while the petals have deeper range of tones.

Inverted Color Range Mask

Lets darken the tonal curve of the image, but exclude the brightest values on the clock face. To avoid the time-consuming process of selecting them one at a time, let's identify them by their brightness range.


Original grayscale image

Add a Curves adjustment layer. Do not adjust the curves yet.
And a luminosity mask to the Curves layer.
Click on the mask and choose Selection > Color Range...
Check the Invert option.
Specify a high brightness value so that only the brightest elements are masked.
Adjust the Fuzziness slider to avoid any abrupt transitions.


We have made an inverted mask which blocks the clock hands.
Our Curves adjustment will affect everything but the clock hands

Edit the Curves adjustment layer to darken the selected values.


Here is the final image:


After masked Curves adjustment.
All of the image has been darkened, except the clock hands.

Blend If

Let's deepen the tonal curve of the image, but affect only the white paint.


Original grayscale image

Duplicate the background layer, creating a layer named Layer 1
Change the Blend If options of Layer 1 to select only the white paint


The brightest values have been selected

Apply a Curves adjustment to Layer 1

Here is the final image:


After Curves adjustment to the selected range
The white paint has a deeper range of tones