The Circle of Confusion (CoC) , just in case you are confused

This video tries to sort out the confusion on the circle of confusion, its simplified and yes there are many more aspects to it.

[niltonnr]

That was a great explanation. Before it was difficult for me to understand once you get the bokeh effect if it is was inside the circle of confusion or if it was outside. After you explanation I understood that bokeh effect is outside the COC, but the effect is directed influenced by the COC area.

[MondayFeelings]

Thank you for this video. It finally made me understand the relation between CoC and printing sizes!

[barrelcactusaddict]

I'm literally crying right now from frustration. I can't understand WHY changing the aperture on a camera lens changes the depth of field; I read it has to do with the circle of confusion, but I can't understand what the circle of confusion is. What is it? It makes no sense. I'm more of a visual learner, and I cannot comprehend the diagrams. Is there any way you can help me understand? I hate my life right now, I can't even understand the basics. Please can you or someone here help me???😢

[ben-rip]

The image in the video shows light rays coming in parallel from the focused point, but that is not true unless the point is at infinity. Light rays from the focused point hit the lens at every possible point on the lens' outer surface and over a range of incident angles, and the lens then ideally directs that infinite number of incoming light rays passing through it back to a single point on the sensor surface. A perfect lens would do that but a less-than-perfect lens would misdirect each light ray by some small amount, depending on many factors such as radial distance on the lens, surface imperfections, lens materials, lens coatings and materials, etc., etc. The misdirection also depends on light frequency or wavelength. This leads to the circle of least confusion for a single point. With that in mind and using the circle of least confusion for a single point, the rest makes a bit more sense. The theory of a misdirected point image spread out over a square of individual photo sensors is involved and ultimately leads to the permissible circle of confusion. It has to do with perception of how focused a particular magnified print looks at some specified distance to a person with better vision than mine.

[janghys]

Thanks for another good documentation on the physics of light.
However I have a question: in the diagram ( minute 03:00 ) you show us a red beam entering the lens below, and this red beam appears on the sensor ... below? Am I wrong when I expected this red beam pointing on the sensor above the central axis of the lens? Please take this as a compliment. I have to be very thankful for all the explanation you gave us for phenomena we did not know before!
Please continue to make us smarter! :-)

[ianrosie]

Mmm.. in the first two minutes, I couldn't help thinking that the source of chromatic aberration was being used to explain the source of the circle of confusion. I'm sure it's not meant, just the choice of words.

[ben-rip]

I'm more confused than the circle.🙃