Between the struts

This is the view I can have from our balcony and as I often sit there looking at the landscape, and not at the struts, I came to a very strange experience, because I don't see it as shown on the photo, unless I close my left eye and if I close my right eye I see it more or less as follows (see below)

Spot the difference!

So what happens if I open both eyes and try to focus on the whole landscape behind the struts?

The horizontal lines have 'breakages', somehow there are two images which don't coincide or fit together and not only between the struts but also behind the struts. Please note; the struts are larger then drawn( = seen) as one can see behind them. The breakages can be most clearly seen at boundaries e.g. between the large grey field and the forest behind it, or when one looks at cars driving along the road, they jump up and down, including the road.
Again, this is not only between the struts, but also behind the struts.
You can imagine that this puzzled me and I questioned myself what is going on.

I will first show you how I made a photo of what I see, more or less, between two struts and then we can go through step by step what is happening.
I took a photo what I see with my left eye, which is on the photo underneath on the right (!) and took another photo what I see with my right eye (which is on the left in the photo) and then put them together (with photoshop!). And this is more or less what I see if look fairly relaxed at the scene.
The tree in the middle (second large one fro the left)  I could see with both eyes, but they do not totally overlap, but this is difficult to see. The discrepancy is much easier to see with horizontal boundaries e.g road and the two horizontal lines at the bottom of the photo.

Image as seen with both eyes

Image as seen above railing (but with one eye!)

However there can take changes place in the image;

• If I bend my head either towards the right or left then the two horizontal lines can meet and form one line again.
• The interpenetration of the images (left and right) is stronger the further the objects are away from me.
• The interpenetration of the images (left and right) also changes if I put my face nearer the struts.

Let us do a very simple example to get acquainted with the relation between images of far and near objects. This is from the book 'Optik der Bilder' by Georg Maier.

When you focus on background.           When you focus on nearby

The first picture shows what you see when you focus on the cup;
You experience the cup as a physical object which coincides with the image from the left and the right eye. The hands are just images which don't coincide with the actual object and you can more or less look through them.
 
In the second picture it is the other way around. You focus on the stick and suddenly there are two cups.

Now the problem with the struts is that the gap between the struts is smaller then the distance between our two eyes
Let's make a sketch when you look between two struts.

Focusing on background between two stiles

Here it becomes clear that for the right eye the tree in the distance is on the right side of its visual field (red) whereas for the left eye the tree is on the left side of its visual field (blue).
However with my left eye I can see what is for the right eye behind the stick on the right and with my right eye I can see what is for the left eye behind the left stick. So I look behind/through two sticks and my visual field widens.
Here it becomes clear that the two images partly overlap and in how far, depends on the distance of the object one is focusing upon.
Also notice that in actual fact we put  two images together but they are crossed over. So the image on the right is from my left eye and the image on the left is from my right eye. This is not how we usually look at things. When we look at an object, we look with the right eye at the 'right' side of the object and with the left eye at the 'left' side of the object and through this process an object gets the character of a tangible object which occupies space as when we at the stick or at the cup in the above mentioned experiment.

Now imagine a bird from the tree is flying towards you, then the nearer it comes, the nearer the bird comes to the centre of both visual fields, that is for left and the right eye. That is why the image of the object nearer to you becomes more clear and more tangible.

Now the question why the horizontal lines have breakages;
You can do a simple experiment. Have a horizontal stick about a meter or more in front of you and then look between two flat hands at a section of the stick. Your hands should be about 10 cm apart.
Tilled your head a bit so the stick shows breakages.  If you tilt your head to left, that is left eye down and right eye up, the image on the right=(left eye image) goes up and left image (=right eye image) goes down.

But taken altogether one can see that we can squeeze in between the railings and see more then the width between the struts.

Now what do experience when we try to focus on the space behind the strut?

 

Here we can see respectively with our left eye and the right eye the tree, what is for our nose behind the strut. But here it will depend on the width of the strut in how far the images overlap. In this drawing the image of the tree can be seen with both eyes, but if our head is tilted e.g left eye is lower or higher then the right eye, then the image can be above each other. However in this instance the strut more or less disappears, it becomes transparent.

Altogether it becomes clear that what I viewed through the struts is not an illusion. This does not mean that the borders/ horizontal lines are not in line or that cars are bobbing up and down, but once we work out what is happening we understand how it comes into being.

However the experience that cars are bobbing up and down and the road is cut into pieces etc is a real experience.