Aperture and Field of View

[swansont]

6 minutes ago, Strange said:

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

And he blames everyone else for this...

[Strange]

1 hour ago, Dalo said:

That is why I proposed the experiment.

Can you confirm if zero, one, or more of the following illustrate the experiment you wish to perform. And if none, why not.

[Dalo]

4 hours ago, Strange said:

Can you confirm if zero, one, or more of the following illustrate the experiment you wish to perform. And if none, why not.

From up to down.

1) The first drawing should have a diaphragm as well, open all the way. That would be the initial situation.You could use the third drawing, but then the opening is smaller than the opening of the second drawing where only 3 beams pass through. That would be confusing.

2) The second drawing would correctly show three bright spots on the screen, representing the three beams which have gone through the diaphragm.

3) The third drawing needs to make clear that the lines do not represent the beams (which have been dimmed), but their sources, which I called lamps or mini suns. The  five projections on the screen would represent the fact that even though the position and size of the aperture is equal to the previous drawing, where only three beams passed, we can nevertheless see five spots representing the sources.

It is therefore imperative that the same position of the diaphragm be used for all situations, the only difference being the size of the aperture and the number of beams going through it.

I hope I will not need to confirm once again that a change of aperture does not affect the field of view, but only the number of beams that can pass through the aperture. That is what makes this experiment interesting in my eyes: three beams, five lamps/mini suns.

I do not know if the result will be as I predict, that is why I hope to see it done one day, by me, or by somebody else.

Edited November 30, 2017 by Dalo

[Strange]

54 minutes ago, Dalo said:

It is therefore imperative that the same position of the diaphragm be used for all situations, the only difference being the size of the aperture and the number of beams going through it.

Do you have any preference for the position of the diaphragm?

Let's stick with the simplest, and the most realistic: keeping it at the focal point.

Here it is with the diaphragm fully open:

And, as expected, we can see all 5 light sources on the film/sensor.

 

And now here it is with the diaphragm closed down.

And, not surprisingly, we can still see all 5 light sources on the film/sensor.

Are you happy with that? 

(No one is going to do the experiment for you, so this will have to do.)

OK. You like the idea that some beams that should be blocked. Lets move the diaphragm adjacent to the lens:

Here it is with the diaphragm fully open:

As expected, we can see all 5 light sources on the film/sensor.

 

And now here it is with the diaphragm closed down:

Now we can see just the 3 light sources that are not blocked (shadowed) by the diaphragm.

So, is there anything else to say?

Edit:

Actually, it might be worth making one small point: as the lasers are not perfect, you will probably still see a faint image of the two blocked sources. (Because, as we have already established, reducing the aperture does not change the field of view.)

And, of course, placing a filter anywhere will not make any difference to any of the above (apart from reducing the light level in all cases).

Edited November 30, 2017 by Strange

[Dalo]

14 minutes ago, Strange said:

Do you have any preference for the position of the diaphragm?

Let's stick with the simplest, and the most realistic: keeping it at the focal point.

Here it is with the diaphragm fully open:

And, as expected, we can see all 5 light sources on the film/sensor.

 

And now here it is with the diaphragm closed down.

And, not surprisingly, we can still see all 5 light sources on the film/sensor.

Are you happy with that? 

(No one is going to do the experiment for you, so this will have to do.)

OK. You like the idea that some beams that should be blocked. Lets move the diaphragm adjacent to the lens:

Here it is with the diaphragm fully open:

As expected, we can see all 5 light sources on the film/sensor.

 

And now here it is with the diaphragm closed down:

Now we can see just the 3 light sources that are not blocked (shadowed) by the diaphragm.

So, is there anything else to say?

Now you start with the second phase of the experiment. The dimming of the beams with a filter or otherwise.

It is obvious that when the diaphragm is completely open, we will see projected on the screen five spots representing the five sources.

The question now is: will we still see five sources with the diaphragm at the same position, the one in which it blocked two beams, or only three sources projected on the screen?

[swansont]

9 minutes ago, Dalo said:

 The question now is: will we still see five sources with the diaphragm at the same position, the one in which it blocked two beams, or only three sources projected on the screen?

Adding a filter will not make beams appear. You can't "still see five sources" when you don't have five beams to begin with. (Two were blocked)

[Strange]

12 minutes ago, Dalo said:

The question now is: will we still see five sources with the diaphragm at the same position, the one in which it blocked two beams, or only three sources projected on the screen?

Hmmm... let me think about that...

31 minutes ago, Strange said:

And, of course, placing a filter anywhere will not make any difference to any of the above (apart from reducing the light level in all cases).

That's it.

[Dalo]

7 minutes ago, swansont said:

Either you close (or move) the diaphragm, or you add a filter. Not both.

I do not see why.

1) The diaphragm must keep the same position for the whole experiment.

2) the aperture, opening of the diaphragm can be varied.

3) The filter is applied to the source of light, before they enter the lens.

There is only one layout, maybe I should have clearly indicated that the one with the diaphragm place on the focal length is completely uninteresting.

The diaphragm will therefore have to be at a position where all five beams can pass when it is completely open, and only three beams can pass when it is close.

edit: if you still think that a filter should have no effect on the number of sources projected on the screen, with the condition as stated concerning the position of the filter (before the beams enter the lens), then you prediction is exactly the opposite of mine. You may be already convinced that you are right, I would like to see it confirmed by an experiment.

Edited November 30, 2017 by Dalo

[Strange]

1 minute ago, Dalo said:

The diaphragm will therefore have to be at a position where all five beams can pass when it is completely open, and only three beams can pass when it is close.

Adding a filter will only reduce the intensity of each beam. It will not stop it being blocked. 

I am assuming you mean a clear, neutral, photographic quality filter that just reduces the intensity but doesn't, for example, change the direction of the light.

If, on the other hand, you are thinking of a piece of "frosted" (diffuse) glass, then the effect could be depend on where you put the filter. 

[Dalo]

Just now, Strange said:

I am assuming you mean a clear, neutral, photographic quality filter that just reduces the intensity but doesn't, for example, change the direction of the light.

of course.

It is now clear where we both stand. I think a further theoretical discussion will not bring up any new facts or make us change our respective mind.

 

[Strange]

Just now, Dalo said:

I think a further theoretical discussion will not bring up any new facts or make us change our respective mind.

And neither will an experiment.

[pzkpfw]

This whole 5 laser thing still seems like a pointless diversion, as I think Dalo has misunderstood post #2 (which he seemed to accept).

Dalo, the diagram showed how light from one point on the source travels multiple paths to the lens. So the diaphram blocks some of the light from points on the source, but not all. Note how in post #2 the diaphram does not cut off the head of the stick figure; just some of the light from the head. I've slightly expanded the diagram, possibly wasting my time.

Your five lasers do not replicate what happens for general photo taking, as we don't get single sources of light from the source we are photographing. e.g. there won't be a single ray of light from the head of the stick figure to the lens.

 

Edited November 30, 2017 by pzkpfw

[Strange]

2 minutes ago, pzkpfw said:

This whole 5 laser thing still seems like a pointless diversion

Although, as always, Dalo has changed what he is "really" interested in since the original question. Just a symptom of his chaotic thinking or a deliberate attempt to derail his own threads? I don't know.

4 minutes ago, pzkpfw said:

Your five lasers do not replicate what happens for general photo taking

Indeed. I have no idea if Dalo either understand or cares about that.

[Dalo]

35 minutes ago, Strange said:

Although, as always, Dalo has changed what he is "really" interested in since the original question. Just a symptom of his chaotic thinking or a deliberate attempt to derail his own threads? I don't know.

Indeed. I have no idea if Dalo either understand or cares about that.

not true. I kept the same model the whole thread. Sometimes I used analogies to clarify what I meant. But if you read my posts carefully you will see that I remained consistent all along.

Concerning the 5 laser beams, they are essential to the experiment. 

[Strange]

1 minute ago, Dalo said:

I kept the same model the whole thread.

You appear to have changed the question. From field of view to some nonsense about filters.

[Dalo]

2 minutes ago, Strange said:

You appear to have changed the question. From field of view to some nonsense about filters.

Not true. I cannot help it if you are unable to read texts without being blinded by your prejudices.

[pzkpfw]

1 minute ago, Dalo said:

Not true. I cannot help it if you are unable to read texts without being blinded by your prejudices.

How about you draw a diagram of what you expect to happen with your combination of filter and diaphragm?

[Strange]

4 minutes ago, pzkpfw said:

How about you draw a diagram of what you expect to happen with your combination of filter and diaphragm?

Good luck with that.

[Dalo]

When the diaphragm is completely open, five beams pass through the aperture, three when it is closed.

My prediction is, when the (neutral) filter is used, five light sources will be projected on the screen, even if the aperture would only let three beams through.

I am not a talented artist, and the way the beams are refracted is certainly not realistic.

 

Edited November 30, 2017 by Dalo

[Strange]

35 minutes ago, Dalo said:

When the diaphragm is completely open, five beams pass through the aperture, three when it is closed.

My prediction is, when the (neutral) filter is used, five light sources will be projected on the screen, even if the aperture would only let three beams through.

I am not a talented artist, and the way the beams are refracted is certainly not realistic.

Well, thanks for trying. Here is my version, let me know if I have got it right.

First, without the filter (we've seen this before):

Now let's insert the filter:

As the filter doesn't change the path of the beams, it won't change whether they are blocked or not.

Can you explain why you think adding the filter might make the blocked lights visible?

[pzkpfw]

I greatly appreciate the effort, but that does not at all explain why you think the filter will have any effect.

Your diagram shows the diaphragm open to a point where all 5 rays go through. The filter won't change that.

The key is - when the diaphragm is closed a bit so only 3 rays go through - what effect is the filter having?

... that's the bit you need to diagram.

 

[Dalo]

19 minutes ago, Strange said:

Can you explain why you think adding the filter might make the blocked lights visible?

I already did, but I will say it again.

You have to imagine that the filter is being used, and that the diaphragm is completely open. In such a situation it is to be expected that all five light sources will be visible on the screen. Such a situation is comparable to any other scene being projected through a lens on a screen. Closing or opening the aperture should have no effect on the field of view, and all the five sources will remain visible whatever the aperture.

In other words, closing the aperture will have an effect on the number of beams passing through the aperture, but not on the number of light sources projected on the screen.

It is of course only an abstract prediction that must be confirmed, or infirmed, empirically.

I do not have a full fledged theory to justify my prediction, but I would like to know first what its value is.

Edited November 30, 2017 by Dalo

[Strange]

1 minute ago, Dalo said:

You have to imagine that the filter is being used, and that the diaphragm is completely open. In such a situation it is to be expected that all five light sources will be visible on the screen. Such a situation is comparable to any other scene being projected through a lens on a screen.

No. Projecting five parallel laser beams through the system is NOT the same as "any other scene". 

Several people have explained why these are very different scenarios. 

Quote

Closing or opening the aperture should have no effect on the field of view, and all the five sources will remain visible whatever the aperture.

In the case of your five lasers, closing the diaphragm WILL block two of the beams and so only 3 sources will be visible. Adding a filter will not change that.

In the case of "any other scene" then the entire scene will remain visible if the diaphragm is closed.  Adding a filter will not change that.

4 minutes ago, Dalo said:

It is of course only an abstract prediction that must be confirmed, or infirmed, empirically.

It can also be confirmed by theory.

Quote

I do not have a full fledged theory to justify my prediction, but I would like to know first what its value is.

The value of your prediction is: false.

[Dalo]

4 minutes ago, Strange said:

No. Projecting five parallel laser beams through the system is NOT the same as "any other scene". 

when using the filter the beams are not visible anymore, only the light sources. In this sense, it is just like any other scene.

Your judgment expresses your confidence in the theory, and there is nothing wrong with that. That does not mean that an empirical confirmation would be superfluous.

Edited November 30, 2017 by Dalo

[Klaynos]

4 minutes ago, Dalo said:

when using the filter the beams are not visible anymore, only the light sources. In this sense, it is just like any other scene.

Your judgment expresses your confidence in the theory, and there is nothing wrong with that. That does not mean that an empirical confirmation would be superfluous.

Are you suggesting that the filter completely removed the lasers so they are not dominating the response of the sensor and then you are illuminating the scene with some other light (e.g. room lights) and can image the front of the laser sources?

If so you are mixing your situations and need to review the first few posts of this thread and where it has been explained to you again and again how non laser sources are radiating in all directions so there are rays (in ray optics) hitting all parts of the lens. There are some nice diagrams above showing this.