Imagine we have a panel of lasers in a truly dark vacuum, together with a panel of sensors, facing each other, some distance apart.

Further, imagine that the number of lasers within the light-panel is exactly the number of sensors in the sensor-panel, and that each laser points directly at exactly one sensor.

There is, therefore, a perfect 1-to-1 mapping between the light sources and the light sensors, and no other source of light, producing a single perceived object upon the sensor-panel.

If we move the light-panel away from the sensor-panel, without rotating it in anyway, there will still be a perfect 1-to-1 mapping between the light sources and the light sensors, regardless of how far apart they are, subject of course to the accuracy of the lasers within the light-panel.

This implies that there shouldn't be any change in the perceived size of the light-panel as it moves away -

The luminosity at each sensor is always going to be exactly the same, regardless of the distance between the light-panel and the sensor-panel.

This appears to be an example of a receding light source that does not have a vanishing point, and therefore, would not be perceived intuitively, but would instead appear to have a constant size.

Is anyone aware of similar hypotheticals, or of a criticism of this hypothetical that suggests otherwise?


The notion of apparent size that you're using here doesn't match up with the usual notion of image size in optics. By your definition, an object like a light bulb or the sun has infinite apparent size since it illuminates your entire sensor panel regardless of the panel's size. It would get dimmer as it moved away, but not "smaller".

Your laser panel is essentially a hologram of a point source at infinity. (A point source at infinity produces parallel rays, and the laser panel is a hologram because it emits the same rays that that source would emit despite not being at the location of the apparent source.) If you pointed the laser panel at an autofocusing camera or eye, it would focus to infinity and the image would be a single point, so the panel has an apparent size of zero by the usual definition.

The effects of the laser panel are independent of the distance to the panel essentially because the relevant distance is the distance to the apparent source, which is always infinite. If you de-idealize it a bit by making it a hologram of a light source of nonzero size at a large but finite distance, then the angular size and apparent magnitude of the image in a camera/eye will decrease with the distance to the apparent source, not the actual source, so they will fall off more slowly than you might expect if you think of the laser panel as the source.


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