And this is f2.

And it's for focus.

That's our directrix and it has the equation y is equal to k.

The scaling factor was 1.

And you enter that space, and you feel like, Wow!

That's the point.

Focal length

Focal

Focal Length

Focal blur

Focal point

First Focus

Second Focus

Focal Length

Focal length

Focal length of the lens

Well, we just used the distance formula.

Or they can be, I don't want to say always.

So let's call that a directrix.

It's equidistant from a focus and a directrix, where this is the focus.

And hard to keep focus.

I'll call that well, we'll call that a focus because it will be a focus.

But where's the focus point?

An object at range of 100 meters

We have focused on the worst case scenario.

Set here equivalent focal length assuming a 35mm film camera, in mm. A value of 0 means the focal length is unknown.

Construct an ellipse with this focus

I'll do it on this right one here.

And what we want to do is, we want to find out the coordinates of the focal points.

Ellipse by Focuses Point

It looks something like that.

35mm equivalent focal length

That's this distance right there.

And that's what we set out to figure out in the beginning.

Requires great focus.

Just focus.

Bifocals.

Your focus,

Construct a hyperbola with this focus

Construct a parabola with this focus

Or b which is, remember, what was b?

Just remember, you're going 1 over 4A below the vertex.

This is f1, this is f2.

Fair enough.

Hyperbola by Focuses Point