Simulate Twilight

The idea for this exploration is a painting by French surrealist Rene Magritte, depicting the front façade of a house at twilight. The front of the house is bathed in shadows, with a porch light illuminating the doorway. The dynamic thing about the painting is the sky. It's bright and illuminated, as if it were the middle of the day.

Each time I look at Magritte's painting, and even now as I recall it in my mind, I'm undecided as to whether this is a true distortion of reality or merely a depiction of that elusive moment where daylight slips into night. Whether or not the sky is really that light when shadows fall, there's no denying that it makes for an evocative image.

The keys to making the effect convincing are an understanding of how light is cast on various surfaces, an interesting sky area, and an interesting overall composition.

Siena Backstreet
Nikon D2H
1/125 sec, f/5.6
Focal length 42mm

About the Original Image

The original photo is a picture of the rooftops of Siena, looking towards the cathedral. At first look, it's not much of a photograph…the primary landmarks are all but hidden and obscured, and the main buildings are pretty scruffy and beat up. We have antennae, satellite dishes, and an overall absence of a primary focal point.

And yet, for this exploration, this photo is a great choice. First of all, the sky is very solid, filling the top half of the image with rich color and puffy clouds. And the irregular tile shapes that jut up into the sky create an interesting pattern that's far better than if it were simply a flat straight skyline. And although the buildings appear a bit rough, the geometry of planes and shapes is quite interesting, and as you'll see, we're going to create our own dynamic focal point.

Building the Effect

To approach this exploration, I needed to think about the different lighting zones within the image and isolate the tonal values for those zones in separate layers. I needed to create a lighting value for the sky, as well as for the deep shadows in the buildings, and another for the illuminated areas within the buildings. The trick when separating the lighting areas is to visualize the relationship between these tonal areas holistically, and be able to articulate exactly the right tone for a given area without being distracted by other areas that might be way off.

Defining Lighting Zones

For example, my first tonal area was the building illumination areas, which I wanted to have a warm, incandescent glow. I selected Curves from the Adjustment Layer pull-down menu in the Layers palette, and modified the curve as follows: I selected Blue from the Channel pull-down menu and added a single curve point with a value of Input: 139, Output: 91, which increased the amount of yellow in the image. I then selected the Red channel and added a single curve point with a value of Input: 112, Output: 142, which added a bit of red. Finally, I reset the Channel pull-down menu to RGB and added two curve pointsInput: 18, Output: 41, and Input: 137, Output: 217which brightened the image overall (see Figure ).

Creating the warm color tones.

To create the dark tones of the buildings, I dragged the Background layer to the Create New Layer icon in the Layers palette to duplicate it, and then dragged the new layer to the top of the layer stack. I chose Image, Adjustments, Curves and modified the new image layer by adding three curve points: Input: 59, Output: 12; Input: 105, Output: 50; and Input: 181, Output: 158. Because this was a duplicate layer and I wanted to keep the layer stack concise, I clicked OK, applying the Curves correction directly to the layer, which I named Dark Bldgs (see Figure ).

Creating the dark building tones.

Creating the Bright Sky

I duplicated the Background layer a third time so that I could create a lighter layer for the bright sky. After positioning it as the uppermost layer in the layer stack, I applied a curve directly to the duplicate sky layer which had two data pointsInput: 61, Output: 115 and Input: 203, Output: 238. I named this third layer Bright Sky, and with it still active, I set about the rather tedious task of selecting the skyline so that I could mask the lower half of the layer. I started by selecting the Magic Wand tool from the toolbox and attempting to select the sky area. If I could do this, I could then simply invert the sky selection to select the buildings.

In the Options bar, I set the Tolerance to 44 and began selecting the sky, Shift-clicking to add areas to the selection. After the large areas were filled in, I selected the Lasso tool and circled the smaller islands that were left over, making sure to hold down the Shift key throughout the process to add each section to the global selection area.

In the process of selecting the sky, I inadvertently selected areas of the tower as well as the blue dome. In addition, many of the detail areas, such as the cross and statues at the tops of the buildings had been absorbed into the sky selection. To clean up these details, I entered Quick Mask mode by clicking the Quick Mask icon (the lower-right corner of the toolbox, beneath the background color swatch). This action placed a mask over the unselected areas, leaving the selected area clear (you can reverse this by double-clicking the Quick Mask icon and choosing Selected Areas from the Color Indicates section).

I selected the Brush tool with a small brush size and the foreground color set to black. I painted in the mask to subtract from the selected area, using the Zoom tool as necessary to see all necessary details. Finally, I clicked the Standard Mode icon (to the left of the Quick Mask icon), to exit Quick Mask mode and apply the selection to the sky. I then clicked the Add Layer Mask icon in the Layers palette to mask the lower buildings, revealing the Dark Bldgs in the lower layer against the bright sky (see Figure ).

Lightening only the sky.

Illuminating the Buildings

With the dark buildings and the sky working together, it was time to introduce the building illumination tones I'd created earlier. I highlighted the Dark Bldgs layer in the Layers palette and added a layer mask. I wanted to add a glowing light bulb to the center of the building area, illuminating the dark niche. I selected the edges of the building that would define where the light would fall, faithfully tracing the edges of the tile roofs and edges of the buildings and satellite dish. I also selected the area on the right in the same way. Then I selected the Brush tool with a 300-pixel brush and black as the foreground color. I also set the Opacity in the Options bar to 23%, and began lightly painting the mask in the building areas. I varied the Opacity further and gently feathered the mask to create a subtle lighting effect (see Figure ).

Adding the illuminated buildings.

Now that I had illuminated some of the buildings, I wanted to darken the surrounding buildings a bit more to add a additional contrast. I added a Curves adjustment layer above the Dark Bldgs layer, with two curve pointsInput: 38, Output: 25, and Input: 221, Output: 163. This adjustment darkened the light areas in the dome and tower, although it also flattened the shadows. I added a layer mask and painted the mask into the shadows to make them a bit brighter (see Figure ).

Darkening the buildings.

The final step was to add the light bulb in the lower building area. I clicked the Create New Layer icon in the Layers palette to add a new layer above the Background layer and highlighted the layer name, renaming it Light. I selected a large feathered brush and sampled a yellow orange color from the illuminated wall area. With the Brush opacity set to 11%, I lightly painted in the glow with a single click. I gradually made the brush smaller and the foreground color brighter, clicking in the same spot repeatedly. Because I was working in a separate layer, I selected the Move tool and repositioned the "light bulb" to find the proper placement (see Figure ).

Adding the light bulb.