Light Study in Photoshop

Simulating Light Behaviour in Photoshop

Often, we want to create realistic and convincing images with Photoshop. One of the most essential factors contributing to realism is light. By studying how light behaves in the real world, we can simulate it in Photoshop to achieve more believable images.

Understanding Light Behaviour

In our Physics lessons at school, we have been introduced to the concepts of reflection and refraction of light. This concept alone can be put to use in Photoshop or any other graphic programs, with a little thinking.

Before applying lighting concepts, we have to first set up an object to work on. Let's start with a big empty canvas with a white background. On a new layer, draw the silhouette of a box and colour it a light greyish-blue shade.

My silhouette is drawn in such a way that it is viewed from a perspective. The dashed lines should help you imagine the perspective view of my object.

To transform this plain shape into a box, we shall shade the regions accordingly. In this example, we shall assume that light falls from above. Therefore, the region facing upwards should be the lightest portion.

However, we should not use the Dodge Tool to lighten the upper face because the colour is already pretty light. Instead, we are going to darken the other two faces using the Burn Tool. Generally, I make one face a little darker than the other to bring out the shape.

In the screenshots, I used to Marquee Tool to select the face to be darkened because this will create a nice contrast between the faces. With this done, we should have a very basic shaded block, with the light source shining above the object.

In the next page, we shall discuss about how light reacts to different materials, as well as the reflection and refraction of light. Of course, we are going to simulate it in Photoshop, so there will be no detailed theoretical Physics talk.

Emphasising Light on Objects

After we have our basic block shaded to define lighter and darker areas, now we have to place some emphasis on the light itself. Keep in mind that we have determined the light source to be above the block.

Use the Dodge Tool to shade the upper face. For your reference, I used "Highlights" for the Range, and 50% for Exposure. You should experiment with different settings (especially the Range) on different colours when simulating different objects with different materials.

As in my image above, dodging the upper face in that manner creates a glassy feel because the light is strongly reflected. For a plastic material, I would use a setting with less exposure and a midtone range.

Immediately after shading a light source on an object, you should shade the corresponding shadow:

Unless the light source is really strong, most shadows formed in real world situations are rather fuzzy. In this case, I used a big and fuzzy brush to paint the shadow area black, and then used the Eraser Tool to erase excess portions.

Reflection of Light

Since our block has a rather glassy property, it would reflect colours from the surrounding. In the image above, our block sits on a white surface. Therefore, we would shade the parts close to the white surface lighter.

In the image above, the arrows represent the light rays from the white surface bouncing off the block surface, hence the lightening of the corresponding light surfaces.

Similarly, light rays from the block will be reflected on the floor surface. However, we won't shade the floor greyish-blue because the resulting effect would look rather fake. Instead, we are going to create a clear reflection of the block on the surface.

First, select a thin portion of the block with the Marquee Tool, as shown in the image.

Then, copy and paste it onto a new layer and stretch it using the Transform Tool (CTRL + T).

Next, put the stretched layer under the "shadow" layer:

Finally, use the Eraser Tool to erase excess "reflection" so that it lines up nicely with the borders of the block.

And with that, our reflective glass block is done!

Conclusion

A little observation and careful planning goes a long way when creating images in Photoshop. Therefore, whenever you have an idea to start a new image, looking for examples and reference will be a great help along the way.