5. OpenCV Tutorial - Learn Classic Computer Vision & Face Detection (OPTIONAL)/3. How are Images Formed.srt

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So let's talk a bit about how images are formed.

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So we're going to look at the most basic example of an image formation onto a piece of film.

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So imagine you're outside in a park and you're holding a strip of film while facing a tree so light

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reflects off the tree at different points and bounces off a tree onto your piece of film.

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So as you can see in this example what happens here is at the top of the tree and the middle of the

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tree are going to reflect at similar points along the farm.

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That's not good.

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That will actually focus that will basically result in an unfocused image or blurred image here.

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So as we can see that's not how our eyes or cameras work.

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This is a best example of how our eyes and cameras work.

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We essentially use a barrier to block off most points of light while leaving a small gap here and that

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gap has called aperture.

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And this allows us some points of light to be reflected onto the form.

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So this gives you a much more focused image and that's actually the basis of a pinhole camera.

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So it is a problem with a simple pinhole camera model in that the aperture is always fixed.

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So that means that a constant amount of light is always entering this will which can be sometimes overpowering

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for the film.

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Meaning that everything is going to look white.

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And secondly we can focus using this fix up issue to focus the image even better although it's never

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going to be as bad as the previous image.

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We still need to move the film back and forth.

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And that's not really a good system.

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So how do we fix this.

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Well by using a lens and an adaptive lens which is what most modern cameras and our eyes use it allows

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us to control the aperture size and in photography aperture size is referred to as f stops and cameras

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and lowa is better and also allows us to get some nice depth of field which is also called booka in

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photography.

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Just so you know book Booker is a highly desirable trait in photography.

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It allows us to have very blurred backgrounds while we focus on a growing image resulting in a pretty

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nice effect.

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Secondly with using a lens you actually can control the lens wit which allows us to instead of moving

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the film back and forth.

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We actually use a lens to focus directly on this point here.

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This results in a very nice nicely controlled system so fiercely before discussing how computers two

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images.

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I think it's good to discuss how humans see images and it is one thing you shouldn't know humans are

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exceptionally good at Image Processing starting with our eyes they're remarkably good at focusing quickly

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seeing in varying light conditions and picking up sharp details and then in terms of to putting what

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we see humans are exceptional at this as we can quickly understand the context of different images and

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quickly identify objects faeces you name it we can actually do this far better than any computer vision

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technique right now.

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And our brain our brains do this by using six layers of visual processing that you can see here.

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I won't go into the details of this but it's incredibly complicated.

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And if you're curious you can visit the Wikipedia page on our visual system right here.