Rear View Mirrors: Objects Closer Than They Appear

[Buckleymanor]

Are you sure these are convex mirrors?
Sorry to hear you had an accident, but frankly it is difficult to take some of the things you say seriously. I never use any mirror, even flat ones, to gauge where another car is if I really need to know that information. If I need to switch lanes or make a turn, I always look directly at the space where I want to go to, to see if anything is in the way.

Absolutely you can see the difference quite clearly when looking at an object like a wall directly behind.
The two side mirrors show the wall to appear a further distance away than the rear view mirror.
Both the images in the side view mirrors appear to be at the same distance.
Done it checked it.

 

[DaveC426913]

The last comment stop before I killed someone was making a mountain out of a mole hill.

No it isn't.
1] That is not the appropriate expression for such a situation.
2] You are using the mirror incorrectly (as evidenced by the fact that you thought you could use them to judge distances and that you said you have had difficulties with using them this way), and that is dangerous.

suguested that the side mirrors could be made in a similar way.

They can't be made the same way. The geometry is all wrong. The rear view mirror is a foot from your face. The side view mirror can be as much as 3-4 feet from your face. This makes for a useless field of view.

 

[Buckleymanor]

No it isn't.
1] That is not the appropriate expression for such a situation.
2] You are using the mirror incorrectly (as evidenced by the fact that you thought you could use them to judge distances and that you said you have had difficulties with using them this way), and that is dangerous.

O! yes it is you made a total exageration and was a bit rude too.

They can't be made the same way. The geometry is all wrong. The rear view mirror is a foot from your face. The side view mirror can be as much as 3-4 feet from your face. This makes for a useless field of view.

What do you drive a crane.The geometry in my vehicles is OK.
The distance from my face to one of the side view mirror is about the same as the distance to the rear view mirror.
Even if it wasn't both mirrors could be positioned so they were, even in your crane.

 

[Doc Al]

The distance from my face to one of the side view mirror is about the same as the distance to the rear view mirror.

The distance to the passenger side mirror is much farther than the distance to either the driver's side mirror or the rear view mirror. More importantly, the angle is such that you need a wider field to see what's coming.

And what are you doing using your mirrors when backing up? Please turn your head and look behind you! (Only in some special cases will I back up using my center mirror--like backing into my garage. But that's it.)

Please stay off the road until you understand how to use your mirrors.

 

[Buckleymanor]

The distance to the passenger side mirror is much farther than the distance to either the driver's side mirror or the rear view mirror. More importantly, the angle is such that you need a wider field to see what's coming.

And what are you doing using your mirrors when backing up? Please turn your head and look behind you! (Only in some special cases will I back up using my center mirror--like backing into my garage. But that's it.)

Please stay off the road until you understand how to use your mirrors.

Just what I expected here is the original post.

They can't be made the same way. The geometry is all wrong. The rear view mirror is a foot from your face. The side view mirror can be as much as 3-4 feet from your face. This makes for a useless field of view.

No need to correct me Dave said and I repeat .The side view mirror can be as much as 3-4 feet from your face.He don't state if it's one or the other side mirrors.
Reckon you should stay of the road until you can read.

 

[DaveC426913]

Reckon you should stay of the road until you can read.

Well somebody's feeling a little wounded...

 

[DaveC426913]

The distance from my face to one of the side view mirror is about the same as the distance to the rear view mirror.

Sorry, I'll spell it out.

Distance is one factor. The other factor is how wide a field of view you need. While it is true that the driver's side mirror is the same distance as the rearview mirror, the requirement for field of view is not the same. Rearview mirror need only show what's directly behind you. Driver's side mirror needs to show everything from your left bumper all the way to the edge of your peripheral vision. This is much wider, and will not be captured by a flat mirror.



(P.S. The difficulty I'm having with you is that you are quick to judge (calling maufacturers "daft") without knowing the purpose or process that led to a design, and do not stop to ask yourself if maybe a hundred years of evolutionary design has given them a modicum of wisdom. I'd be much easier on you if you showed some humility. First, assume people know what they're doing; judge only as a last resort.)

 

[Buckleymanor]

Sorry, I'll spell it out.

Distance is one factor. The other factor is how wide a field of view you need. While it is true that the driver's side mirror is the same distance as the rearview mirror, the requirement for field of view is not the same. Rearview mirror need only show what's directly behind you. Driver's side mirror needs to show everything from your left bumper all the way to the edge of your peripheral vision. This is much wider, and will not be captured by a flat mirror.



(P.S. The difficulty I'm having with you is that you are quick to judge (calling maufacturers "daft") without knowing the purpose or process that led to a design, and do not stop to ask yourself if maybe a hundred years of evolutionary design has given them a modicum of wisdom. I'd be much easier on you if you showed some humility. First, assume people know what they're doing; judge only as a last resort.)

Appreciated though I am trying to get some points across even if I am a bit judgmental.
Earlier in the thread it was mentioned that the drivers side mirror was flat and it was only the passengers side that was convex.
It was pointed out that in the U.K. at least this was not the case and I have a sneaking suspicion that the same applies in the U.S.A.
In effect both side mirrors are convex and with the passengers mirror 3-4 feet further away than the other mirrors does this not cause a certain amount of inconsistency with your argument.

 

[DaveC426913]

In effect both side mirrors are convex and with the passengers mirror 3-4 feet further away than the other mirrors does this not cause a certain amount of inconsistency with your argument.

It's not an inconsistency, it's an interplay between three parameters for the sake of one end result.

Simply put: field of view is the fixed, required end result. The interplay of three parameters will achieve this: the size of the mirror, its distance and its convexity.

Size and distance are factors that are optimaized - but only up to the constraints of the geometry dictated by the car itself. If the FoV is still not met, the only thing left to do is change the optics of the mirror(s) as needed.

 

[Buckleymanor]

Sorry, I'll spell it out.

Distance is one factor. The other factor is how wide a field of view you need. While it is true that the driver's side mirror is the same distance as the rearview mirror, the requirement for field of view is not the same. Rearview mirror need only show what's directly behind you. Driver's side mirror needs to show everything from your left bumper all the way to the edge of your peripheral vision. This is much wider, and will not be captured by a flat mirror.

So to clear things up are the drivers side mirrors in the U.S. convex like the passengers and not flat.Unlike an earlier post that said they were.
If they are convex do they take into account that they are nearer to the driver than the passengers side mirror and have slightly different optics, to allow for the factor of distance.

 

[Doc Al]

So to clear things up are the drivers side mirrors in the U.S. convex like the passengers and not flat.Unlike an earlier post that said they were.
If they are convex do they take into account that they are nearer to the driver than the passengers side mirror and have slightly different optics, to allow for the factor of distance.

All the drivers side mirrors I've seen (in the US) have been flat, not convex. (Although a double mirror is not uncommon, where the smaller top part is convex while the main part is flat.) Only passenger side mirrors are convex.

 

[pallidin]

All the drivers side mirrors I've seen (in the US) have been flat, not convex. (Although a double mirror is not uncommon, where the smaller top part is convex while the main part is flat.) Only passenger side mirrors are convex.

Driver side flat mirror is necessary for accurate distance perception.
Passenger convex mirrors are only intended for "enhanced angular view", NOT for driving while looking at them.

Basically, the convex mirrors, though producing a distorted distance image, allows a "threat" observation only. Do not try to change lanes while only viewing a convex mirror. Do, however, glance at that to determine your threat environment.

 

[Buckleymanor]

All the drivers side mirrors I've seen (in the US) have been flat, not convex. (Although a double mirror is not uncommon, where the smaller top part is convex while the main part is flat.) Only passenger side mirrors are convex.

Can this be true.
Daves allready stated.

You completely skipped over the salient bit, which answers your question quite nicely:


If the mirrors were not convex, the field of view that they displayed of what is behind the driver would be so narrow as to be useless (I've done this, it's useless).

And

The difficulty I'm having with you is that you are quick to judge (calling maufacturers "daft") without knowing the purpose or process that led to a design, and do not stop to ask yourself if maybe a hundred years of evolutionary design has given them a modicum of wisdom. I'd be much easier on you if you showed some humility. First, assume people know what they're doing; judge only as a last resort.)

Driver's side mirror needs to show everything from your left bumper all the way to the edge of your peripheral vision. This is much wider, and will not be captured by a flat mirror.

Me thinks someone else should show a modecum of humiliation.

 

[Doc Al]

Can this be true.

It's true. What pallidin stated in post #42 is essentially correct. (See: http://www.garamchai.com/askadesi/ask07.htm" ; it seems accurate to me.)

Daves allready stated.

Dave's statement about driver-side mirrors in the US being convex is incorrect.

In my experience, most folks do not know how to adjust their (flat) driver-side mirror to eliminate most of the blind spot. When you glance at your driver-side mirror you should not see the side of your car.