Aperture and Field of View

[Dalo]

Just now, Strange said:

With omnidirectional light sources (multiple paths) or with lasers aimed towards the centre of the lens they will not disappear.

I do not understand where you get those omnidirectional light sources from. We are talking about 5 beams just like in the video.

[Strange]

2 minutes ago, Dalo said:

I do not understand where you get those omnidirectional light sources from. We are talking about 5 beams just like in the video.

As I say, with 5 parallel beams, you will get the outer ones blocked by the diaphragm.

I am trying to explain why this doesn't affect the field of view which was, as I understand it, the question you were asking. If you don't want to understand that, we are done.

[Dalo]

You are playing dumb, and it certainly does not suit you.

In one case the image contains 5 elements when the aperture is completely open, in the other case it contains only three after the aperture has been closed.

So, even if you want to be a purist, you will have to admit that closing the diaphragm affects what comes through the lens in one way, but not in the other.

Also, if my assumption is correct, then we still do not have an explanation for this discrepancy.

You may of course withdraw from the discussion at any time.

[Strange]

6 minutes ago, Dalo said:

In one case the image contains 5 elements when the aperture is completely open, in the other case it contains only three after the aperture has been closed.

What do you mean by "the one case" and "the other case"? Do you just mean "aperture open" and "aperture closed"? If so, my diagram explains why the light from the outer lasers gets blocked.

Quote

So, even if you want to be a purist, you will have to admit that closing the diaphragm affects what comes through the lens in one way, but not in the other.

Again, not sure what you mean by "one way" and "the other".

It affects the case of 5 laser beams parallel to one another.

It doesn't affect the case of light coming omnidirectionally from a normal photographic scene, and therefore it doesn't change the field of view.

I have tried to explain the reasons for this. I'm not sure why the explanation isn't satisfactory.

8 minutes ago, Dalo said:

Also, if my assumption is correct, then we still do not have an explanation for this discrepancy.

What is your assumption? And what is the discrepancy?

Your posts are so vague it is very hard to understand exactly what conditions you are talking about, what you think will be the result and why you think there is a problem.

 

[Dalo]

1 minute ago, Strange said:

What do you mean by "the one case" and "the other case"? Do you just mean "aperture open" and "aperture closed"? If so, my diagram explains why the light from the outer lasers gets blocked.

Again, not sure what you mean by "one way" and "the other".

It affects the case of 5 laser beams parallel to one another.

It doesn't affect the case of light coming omnidirectionally from a normal photographic scene, and therefore it doesn't change the field of view.

I have tried to explain the reasons for this. I'm not sure why the explanation isn't satisfactory.

What is your assumption? And what is the discrepancy?

Your posts are so vague it is very hard to understand exactly what conditions you are talking about, what you think will be the result and why you think there is a problem.

 

goodbye.

[Strange]

Glad to be of assistance. 

[Dalo]

I still hope somebody will perform the experiment and make a video of it.

 

edit: I don't know who downvoted me, and I really do not care. It is obviously someone who has no idea what the meaning of the experiment is. I think that Strange understands it perfectly, but is victim of what is called cognitive dissonance. That is is why he tries so very hard to make it sound like I am the one who is unclear.

Edited November 29, 2017 by Dalo

[Strange]

29 minutes ago, Dalo said:

I think that Strange understands it perfectly

I do understand it. (What isn't clear are all your further objections/questions about the result).

Or are my diagrams of the set up wrong? If so, it would be helpful if you said so.

It would actually be quite helpful if you confirmed that they are what you are thinking of. At least that might help pin down any misunderstanding. 

And I have explained what you will see (for the cases I can understand you might be thinking of). But you haven't clearly said what you disagree with and why. (Or what you agree with and why.)

35 minutes ago, Dalo said:

I still hope somebody will perform the experiment and make a video of it.

Feel free to spend $10 and a couple of hours to perform the experiment. But it is pretty easy to predict what the result will be. I'm not sure why you reject that explanation (with no explanation).

 

BTW when you first asked the question I thought you meant "depth of field" and I thought: "I pity the poor so-and-so who attempts to explain that to Dalo".

Then I realised you meant field of view and thought, "interesting question; it should only take a couple of minutes to explain". Yet here we are three pages and three days later. Ho hum.

[Dalo]

1 hour ago, Strange said:

It affects the case of 5 laser beams parallel to one another.

It doesn't affect the case of light coming omnidirectionally from a normal photographic scene, and therefore it doesn't change the field of view.

Yes and yes. What is not explained, and I am repeating myself, is, considering only the first case (of 5 laser beams parallel to one another) how it is possible that even when two beams are blocked, we still can see all 5 lamps from which they originate. Somehow they must emanate rays that go through the diaphragm, while they are at the same time time the sources of the beams that are blocked by the same diaphragm.

If that is the case, images of illuminated objects are not projected the same way as images of beams, because if that were the case, we would, under the same conditions, be able to see the same number of beams and lamps.

What would make perfect sense is that when beams are blocked, the lamps from which they originate should remain invisible even if we reduce the intensity of the beams. After all, what we are seeing is supposed to be light reflected from the lamps whose beams are blocked.

[pzkpfw]

Dalo, do you understand that using 5 laser beams does not replicate viewing 5 points on some object?

That is; say you are looking at a house through some lens and you place lasers on the left, half-way to left, middle, half-way to the right, and right sides of the house ... all pointing direct to you through your lens.

If the aperture were closed a bit so the left and right lasers were not visible to you, do you expect the left and right of the house to also not be visible?

 

[Strange]

16 minutes ago, Dalo said:

considering only the first case (of 5 laser beams parallel to one another) how it is possible that even when two beams are blocked, we still can see all 5 lamps from which they originate.

YOU CAN'T SEE THEM. See the diagrams I provided previously.

You can't see the lasers that are blocked by the diaphragm. As shown in the diagrams I provided.

By the way, when the beams are blocked by the diaphragm, you can't see them. I provided a diagram to show why.

16 minutes ago, Dalo said:

and I am repeating myself

Me too. Do you not actually read what anyone says? That might explain why you never seem to understand.

[Dalo]

7 minutes ago, Strange said:

YOU CAN'T SEE THEM. See the diagrams I provided previously.

You can't see the lasers that are blocked by the diaphragm. As shown in the diagrams I provided.

By the way, when the beams are blocked by the diaphragm, you can't see them. I provided a diagram to show why.

No, you can't see the beams that are blocked. That seems pretty obvious.

Imagine 5 small suns which happen to shine in only one direction. Two are blocked by the diaphragm. Only three spots will be visible on the screen. So far I think that we agree with each other.

Let us now reduce the intensity of the beams by dimming or by using a gray filter. It would make the suns visible while before all we could see were the beams of light.

The question now is: imagine that we are still using the same setup, with the diaphragm at the same position as before, where it let 3 beams through and blocked 2.

How many mini suns will be projected on the screen?

If it is 3, then we have no discrepancy with the number of beams.

If it is 5, then we do have a discrepancy.

[Endy0816]

To the left of the aperture you'll see an image of my ceiling lights.

Most of the light does not come from right in front of the aperture.  This does not represent a problem for the light since it comes in at angle.

An aperture is not a one-way street, light can pass through either way.

Looking through the apperature the other way, you again see the lights.

Now for any laser with minimal spread you merely need to shoot it through the apperature. In that case you'll be able to to see it just fine.

Omnidirectional light != Laser light

I think FOV is basically 180, but really light can travel every which way.

 

Edited November 30, 2017 by Endy0816
sp

[Strange]

4 minutes ago, Dalo said:

Let us now reduce the intensity of the beams by dimming or by using a gray filter. It would make the suns visible while before all we could see were the beams of light.

Why? That makes no sense. 

What is the difference between seeing the sun and seeing the light from it?

5 minutes ago, Dalo said:

The question now is: imagine that we are still using the same setup, with the diaphragm at the same position as before, where it let 3 beams through and blocked 2.

How many mini suns will be projected on the screen?

Putting a filter in the way will just reduce the amount of light. It won't change the path of the rays and hence it won't change what is visible.

11 minutes ago, Dalo said:

Imagine 5 small suns which happen to shine in only one direction.

How are these different from your previous use of lasers?

[Dalo]

1 hour ago, Strange said:

What is the difference between seeing the sun and seeing the light from it?

I am sure you know that you cannot observe the sun directly.

1 hour ago, Strange said:

Putting a filter in the way will just reduce the amount of light. It won't change the path of the rays and hence it won't change what is visible.

When you take a picture with a camera the diaphragm is wide open. Imagine that when you preset  the diaphragm at, say, f/8, two of the five beams are blocked. Before pressing the button, the image is bright because all beams are let through.

Keeping the camera at the same position, you now use a gray filter in front of the beams. Even through the open diaphragm, the scene is much darker. But you can now see all five mini suns.

Since the field of view must remain unchanged, you should be able to see all five mini suns, whatever the aperture.

But f/8 lets only three beams through when no filter is used.

According to your rule, using a filter would change nothing except the amount of light (and therefore the shutter time). That would mean that we should see only three mini sun.

Both possibilities are contradictory.

 

Edited November 30, 2017 by Dalo

[Strange]

7 hours ago, Dalo said:

I am sure you know that you cannot observe the sun directly.

I think you need to get out more. Of course you can observe the sun directly. It may be uncomfortable and dangerous if you do it for too long, but it can be don.

However, this totally irrelevant. Is your inability to focus(*) part of the problem?

(*) Excuse the pun.

7 hours ago, Dalo said:

When you take a picture with a camera the diaphragm is wide open. Imagine that when you preset  the diaphragm at, say, f/8, two of the five beams are blocked. Before pressing the button, the image is bright because all beams are let through.

This is another of your confusing descriptions. You have preset the aperture to block two of the beams. But then you say "before pressing the button" - why is pressing the button relevant if you have preset the aperture? And why bring in more complexities like this? Is it just to drag out the discussion and produce more reasons to pretend not to understand?

Quote

Keeping the camera at the same position, you now use a gray filter in front of the beams. Even through the open diaphragm, the scene is much darker. But you can now see all five mini suns.

And why have you started referring to "suns" instead of "lasers"? Just to confuse the issue?

7 hours ago, Dalo said:

Since the field of view must remain unchanged, you should be able to see all five mini suns, whatever the aperture.

If they are suns (that radiate light omnidirectionally, in all directions) then you will be able to see them, whatever the aperture. Remember, it has already been explained, in detail, why changing the aperture doesn't change the field of view.

And don't complain about me introducing omnidirectionallity; you did that when you moved the goal posts from lasers to suns.

7 hours ago, Dalo said:

According to your rule, using a filter would change nothing except the amount of light (and therefore the shutter time). That would mean that we should see only three mini sun.

I don't know what you think my "rule" is but your conclusion is wrong. Why would a filter reduce the field of view?

Reported for trolling.

[swansont]

16 hours ago, Dalo said:

 
The only, big, difference is that the different sources are perfectly delimited. If a light source is blocked, we know why the image gets darker.
But then how come we are still able to get an image of the blocked source?
It would seem that the reflection of the light source follows another path than the beam.

Light does not follow just one path. "another path than the beam" makes no sense.

Light hits an object and light reflects off of it at many angles. All of the points on the lens are hit with it, and these form an image. There is no "beam" in this situation. Blocking part of the lens makes it dimmer but has no effect on the formation of the image.

 

10 hours ago, Dalo said:

 When you take a picture with a camera the diaphragm is wide open. Imagine that when you preset  the diaphragm at, say, f/8, two of the five beams are blocked. Before pressing the button, the image is bright because all beams are let through.

You need to do a better job of describing the setup, because in a camera, all the beams are going to make it through. The diaphragm does not affect the field of view. I posted photographic evidence of this earlier.

10 hours ago, Dalo said:

Keeping the camera at the same position, you now use a gray filter in front of the beams. Even through the open diaphragm, the scene is much darker. But you can now see all five mini suns.

It's ironic that you demand evidence of others and reject the application of theory, and here you are only giving conjecture without experimental evidence. 

Show us actual pictures that conform to your predictions.

10 hours ago, Dalo said:

Since the field of view must remain unchanged, you should be able to see all five mini suns, whatever the aperture.

But f/8 lets only three beams through when no filter is used.

Again: claimed, but not demonstrated. This is a prediction of yours, based on your (mis)understanding of optics.

I

[Dalo]

26 minutes ago, swansont said:

Again: claimed, but not demonstrated.

agreed. That is why I proposed the experiment.

 

28 minutes ago, swansont said:

Light does not follow just one path. "another path than the beam" makes no sense.

Light hits an object and light reflects off of it at many angles. All of the points on the lens are hit with it, and these form an image. There is no "beam" in this situation. Blocking part of the lens makes it dimmer but has no effect on the formation of the image.

You are changing the premises. We are talking about uni-directional beams, like lasers.

 

2 hours ago, Strange said:

And don't complain about me introducing omnidirectionallity; you did that when you moved the goal posts from lasers to suns.

 

11 hours ago, Dalo said:

Imagine 5 small suns which happen to shine in only one direction.

 

[Strange]

8 minutes ago, Dalo said:

You are changing the premises. We are talking about uni-directional beams, like lasers.

Then why introduce "suns" and filters?

I have explained what will happen in the case of 5 parallel beams. You have ignored this.

I have explained why this does not affect the field of view. You have ignored this.

You have not commented on whether you think this is a reasonable explanation or not, and if not why not. This makes the whole discussion pretty pointless.

You just keep asking the same (already answered) questions and whinging about someone else doing your experiment for you. It is pretty pathetic to see.

You haven't even acknowledged whether my diagram represents the set up you want or not. You are making the discussion pointless and being pretty offensive about it.

But maybe you are only 14. That would explain your lack of knowledge and attitude.

[Dalo]

9 minutes ago, Strange said:

Then why introduce "suns" and filters?

This shows your inability to read posts carefully instead of reacting to your own ideas.

Filters are needed to reduce the intensity of the beams and show the "mini suns" as objects that can be reflected on a screen.

I agree completely that aperture does not change field of view... except in the case of beams. That you ignore this shows how little you have understood my proposal. Denigrating it won't change this fact.

If you think it is pathetic to wait for somebody to perform the experiment instead of doing it myself, why don't you do it yourself and prove me wrong once and for all. Put your money where your mouth is.

I know I do not have the proper gear to do the experiment in a professional way. Maybe you do, or do not care? After all, it is only $10, right?

 

 

Edited November 30, 2017 by Dalo

[swansont]

25 minutes ago, Dalo said:

You are changing the premises. We are talking about uni-directional beams, like lasers.

Then this is trivial. Parallel beams hitting a lens all go through the focal point. Closing down the aperture has no effect on the number of beams.

3 minutes ago, Dalo said:

 That you ignore this shows how little you have understood my proposal. Denigrating it won't change this fact.

Your explanations and descriptions leave something to be desired. Strange is not the only one who has been thrown off track by the wording of your proposals.

[Dalo]

1 minute ago, swansont said:

Then this is trivial. Parallel beams hitting a lens all go through the focal point. Closing down the aperture has no effect on the number of beams.

Do you even read what has been written, or do you just react to isolated sentences?

[Strange]

5 minutes ago, swansont said:

Then this is trivial. Parallel beams hitting a lens all go through the focal point. Closing down the aperture has no effect on the number of beams.

Doesn't this depend where the diaphragm is?

If it is close to the lens (as in the example I as describing) then it will block some beams. If it is near the focal point (as I think it may be in a real lens system) then, as you say, it won't reduce the number of beams.

But as Dalo is not clear (and refuses to clarify) which situation he is thinking about, it is hard to give a definite answer.

4 minutes ago, Dalo said:

Do you even read what has been written, or do you just react to isolated sentences?

Ironic as you still haven't responded to my question as to whether my diagram correctly represents what you are thinking of or not.

Here is another diagram for you to ignore that illustrates swansont's point that if the diaphragm is at the focal point, it has no effect on the number of lights seen. This is probably a far better example than any of my previous ones.

[swansont]

5 minutes ago, Strange said:

Doesn't this depend where the diaphragm is?

Dalo said camera. I assume it's the camera aperture, since he referred to an f-stop.

"When you take a picture with a camera the diaphragm is wide open. Imagine that when you preset  the diaphragm at, say, f/8, two of the five beams are blocked. Before pressing the button, the image is bright because all beams are let through."

 

If the aperture is somewhere else, then blocked beams will not reappear by adding or removing a filter. 

[Strange]

Just now, swansont said:

If the aperture is somewhere else, then blocked beams will not reappear by adding or removing a filter. 

I think we can all agree about that.