Central perspective

The retinal image projects according to the laws of central perspective, yet our final perception undergoes numerous corrections. Therefore, what we are left with to infer the extent of space are converging parallel horizontals and the texture gradient. The railroad tracks running towards the horizon are an example for the first case. Why doesn’t this feature apply to vertical objects? The eye builds up the overall picture of our environment from many individual images by jumping from one prominent point to another. It is forced to do this because the area of sharp vision that we consciously perceive only makes up about 5° of our field of vision. Objects that, because of their size, can only be perceived by joining several of these „individual images“ are corrected in this way because, under these conditions, the brain assumes a straight line as the simplest and most stable construction. Furthermore, perception takes into account the sense of balance and gravity, so we only perceive converging vertical parallels on buildings when we look at them from a very steep angle. However, an object such as a railroad track running straight ahead can suddenly fit into this focus and is not affected by gravity. Consequently, the visual system bases its hypothesis here solely on the retinal image formed according to linear perspective, and we perceive such horizontal parallels as converging according to the rules of perspective. The texture gradient serves us as a clue to spatial depth because we assume that things that look the same are also identical in size. Decreasing distances between such identical objects or their reduced image with increasing distance, like the cobblestones of a street appearing more and more densely packed with increasing distance or the long row of identical telegraph poles moving closer together, runs counter to this and is explained by the conclusion of an existing extension into depth (figure 34, texture gradient 2). However, it is important to note that the texture gradient only contributes to depth perception when we are able to recognize the objects in front of us. Figure 33 (texture gradient 1) shows how this is meant. We cannot recognize the subject, a grassy area, in the photo as it is shown, and therefore the impression of spatial depth does not arise. But if you rotate it 90° counterclockwise, you will immediately see what is meant and also perceive the depth.

A dense tangle of dry, straw-like grass stems overlapping each other, creating a textured and chaotic pattern. The colors are predominantly shades of brown, with hints of green in some areas. When the image is rotated 90° counterclockwise, the impression of depth is created. It is an illustration of how we use the texture gradient as a clue to perceive spatial depth. — Figure 33: Texture gradient 1 When rotated 90° counterclockwise, the impression of depth is created

A narrow paved path winds through a park with grass and trees on either side. Wooden posts and wire fencing run alongside the path, which is lined with lamp posts. The sky is clear, suggesting a sunny day. The wooden boundary posts on the left are all of almost the same size but they recede in the distance and this is an illustration of our perception of spatial depth. — Figure 34: Texture gradient 2 Viewed vertically from above, it would be clear that the distances between the boundary posts are the same.

Railroad tracks stretch into the distance on a sunny day, flanked by tall grass and trees. Houses are visible on the left, and power lines run alongside the track. The tracks recede in the distance anddo not look parallel anymore and this is an illustration of how we perceive spatial depth. — Figure 35: Konverging railroad-tracks

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Main Image creation, Depth and Size

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