Helmet mounted mirror

I went for a ride lastnight to early this morning and watched approaching traffic in my helmet mirror. I'm really surprised that so many state they can't judge distances or closing speeds in theirs.

My mirror is a flat round one that does not distort the image nor the apparent location of objects visible in the mirror. I'm left eye dominate but I do look at my mirror with both eyes at the same time. I checked that a number of times during the ride. Perhaps it's the flat optic of the mirror, the distance it is from my eeye as that distance is further than with an eyeglass mounted mirror or it could be that over the years I've trained myself to be able to judge distances and closing speeds in the mirror.

One my touring bike i have two mirrcycle original mirros on the brake levers and the brake cables run through the shafts of the mirrors. They are round and wide angle and thus objects are a lot closer than they appear in them.. As a matter of fact there is such a difference in the apparent location of objects in the Mirrcycle mirror and the helmet mounted mirror that I don't like using both types on the same bike. Objects that appear so small as to be barely visible in the
Mirrcycle mirror are quite large in the helmet mounted mirror. when I tested the two types of mirrors in conjunction with each other a few years back I'd often see an approaching vehicle in the helmet mirror but would have to search for it in tthe Mirrcycle mirror and that with KNOWING thatthe vehicle was back there.

I've also tried bar end mirrors on my drop bars but didn't like them due to the same wide angle distortion and also because most tims my lower arm blocked my view of the mirror. Another thing with bar end mirrors I didn't like was that hen I glanced down at it I could not see ahead of me at the same time as I can when using a helmet mirror.

One final thing I like about the helmet mirror is that I can scan the entire area behind me simply by moving my head a bit. that comes in handy in turns when i want to see where approaching vehicles behind me are. Many times the bicycle mirrors show me fields or other things but not the road behind me in turns.

Cheers

Sir Ridesalot writes:

I went for a ride lastnight to early this morning and watched
approaching traffic in my helmet mirror. I'm really surprised that so
many state they can't judge distances or closing speeds in theirs.

That isn't the contention. I originally suggested that using one
eye would reduce the ability, but Frank pointed out the binocular
vision is mostly useful at relatively short distances. I confirmed
that with the side view mirror in my car.

My mirror is a flat round one that does not distort the image nor the
apparent location of objects visible in the mirror. I'm left eye
dominate but I do look at my mirror with both eyes at the same time. I
checked that a number of times during the ride. Perhaps it's the flat
optic of the mirror, the distance it is from my eeye as that distance
is further than with an eyeglass mounted mirror or it could be that
over the years I've trained myself to be able to judge distances and
closing speeds in the mirror.

The issue isn't whether you look *at* the mirror with both eyes; given
the way the brain/eye works, pretty much everyone is going to do that
(our eyes typically don't move independently). Those with eyeglass
mounted mirrors typically won't be able to see the mirror with the far
eye; it is blocked by the nose. A helmet mounted mirror may allow a
more foreward position, making it possible for both eyes to see the
mirror. The question, however, was whether you can see, at the same
time, an object in the distance, through the mirror, with both eyes.
You haven't quite answered that. Here's why I think you cannot.

Let

We = eyeball separation
Ww = width of a narrow window
L = distance of point
Lw = distance of window from plane of eyes

To simultaneously see a point that is straight ahead, we must have

(1) We/L = Ww/(Le-Lw)

or

(2) Ww/We = 1 - Lw/L

Typically Lw L, so the right side becomes,

(3) Ww ~ We

In the actual situation the window is a mirror that is positioned to the
side. With the rider facing forward assume that the mirror is adjusted
so that, if his eye were in the center of his face, and looking at the
mirror, he would be looking directly behind.

Assume the mirror is positioned so that the angle from staight ahead to
the mirror is theta. Then the mirror must be rotated theta/2. The
angle theta reduces the effective width of the eyes to We*cos(theta).
The rotation of the mirror reduces its effective width to
Ww*cos(theta/2). As a consequence of this, (3) becomes

(4) cos(theta/2)*Wm ~ cos(theta)*We,

where Wm is the width of them mirror. A practical limitation to
theta is about Pi/4 (45 degrees). With that we get

(5) Wm ~ 3/4*We

My eyes are about 2.5 inches apart. This means I'd need a mirror
that is nearly 2 inches wide. That is certainly doable, but I've
never seen a helmet mounted mirror that wide. How wide is yours?

If you don't follow the math, here's a simple test. Hold your
fingers apart the width of your mirror. Move your hand to where
the mirror is located. Look at a distance object with one eye
closed, then the other. To be able to see both in the mirror
simultaneously, you need to be able to see the point with each
eye, through the window of your fingers. For the mirror widths
I'm familar with, that isn't possible.

--
Joe Riel

On 31/10/14 02:14, Joe Riel wrote:


My eyes are about 2.5 inches apart. This means I'd need a mirror
that is nearly 2 inches wide. That is certainly doable, but I've
never seen a helmet mounted mirror that wide. How wide is yours?

If you don't follow the math, here's a simple test. Hold your
fingers apart the width of your mirror. Move your hand to where
the mirror is located. Look at a distance object with one eye
closed, then the other. To be able to see both in the mirror
simultaneously, you need to be able to see the point with each
eye, through the window of your fingers. For the mirror widths
I'm familar with, that isn't possible.


Couldn't you just ask Sir to close the eye that's closest to the mirror
while trying to look at the mirror? If the view of the mirror is
blocked by Sir's nose, the mirror wont be in view.

--
JS

TAKES practice, eye exercises. There's manual. I'll look n fetch.

Yiu should pracrice with the auto.....quick to the right quick to the right , focus , sdrawkcab sngis daer.

but the raison is a TV helmet with viewing visor.

we asked Lieb for an appraisal but e's hung up on seriw dnuorgrednu

On Thursday, October 30, 2014 6:16:15 PM UTC-4, wrote:
TAKES practice, eye exercises. There's manual. I'll look n fetch.

Yiu should pracrice with the auto.....quick to the right quick to the right , focus , sdrawkcab sngis daer.

but the raison is a TV helmet with viewing visor.

we asked Lieb for an appraisal but e's hung up on seriw dnuorgrednu

eeeeeeeeeeeeeeeeeeeeeeeee

http://goo.gl/t7NwMO

try EYE YOGA

eye ex requires restraint beforeyou twist your head in half from overdoing ....

easy....

try thumb up in out at armslength

daily, follow the tree line.

when you arrive, you will see 3D as standard like with camera spec effects uh the woods scene in F...I see there are 409 quotes...Fahrenheit 451.

I started this with Jimmy Cagney.

off to Lisbon !

'Why is it, he said, one time, at the subway entrance, I feel I've known you so many years ?'

James writes:

On 31/10/14 02:14, Joe Riel wrote:


My eyes are about 2.5 inches apart. This means I'd need a mirror
that is nearly 2 inches wide. That is certainly doable, but I've
never seen a helmet mounted mirror that wide. How wide is yours?

If you don't follow the math, here's a simple test. Hold your
fingers apart the width of your mirror. Move your hand to where
the mirror is located. Look at a distance object with one eye
closed, then the other. To be able to see both in the mirror
simultaneously, you need to be able to see the point with each
eye, through the window of your fingers. For the mirror widths
I'm familar with, that isn't possible.


Couldn't you just ask Sir to close the eye that's closest to the
mirror while trying to look at the mirror? If the view of the mirror
is blocked by Sir's nose, the mirror wont be in view.

Sir says he can see the mirror with both eyes, I've little reason to
doubt that. I've seen pictures of helmet mounted mirrors that project
far enough forward, past the front of the helmet, such that they would
indeed be visible with both eyes. That doesn't mean you can use them
with both eyes to see the same object, but maybe his is really wide.

My immediate thought is that such a location might be less than ideal in
that it creates blind spots for both eyes, something not done with a
more rearward position.

--
Joe Riel

R's facial muscles and related cranial eye synapses were frozen solid in 2003 making independent eye sensor activation improbable

On Thursday, October 30, 2014 6:32:36 PM UTC-4, JoeRiel wrote:
James writes:

On 31/10/14 02:14, Joe Riel wrote:


My eyes are about 2.5 inches apart. This means I'd need a mirror
that is nearly 2 inches wide. That is certainly doable, but I've
never seen a helmet mounted mirror that wide. How wide is yours?

If you don't follow the math, here's a simple test. Hold your
fingers apart the width of your mirror. Move your hand to where
the mirror is located. Look at a distance object with one eye
closed, then the other. To be able to see both in the mirror
simultaneously, you need to be able to see the point with each
eye, through the window of your fingers. For the mirror widths
I'm familar with, that isn't possible.


Couldn't you just ask Sir to close the eye that's closest to the
mirror while trying to look at the mirror? If the view of the mirror
is blocked by Sir's nose, the mirror wont be in view.

Sir says he can see the mirror with both eyes, I've little reason to
doubt that. I've seen pictures of helmet mounted mirrors that project
far enough forward, past the front of the helmet, such that they would
indeed be visible with both eyes. That doesn't mean you can use them
with both eyes to see the same object, but maybe his is really wide.

My immediate thought is that such a location might be less than ideal in
that it creates blind spots for both eyes, something not done with a
more rearward position.

--
Joe Riel

Easy enought to position the mirror so that it doesn't block forward vision to road/trail traffic. I can clesrly see what's in fronto of me.

Cheers

Joe Riel writes:

James writes:

On 31/10/14 02:14, Joe Riel wrote:


My eyes are about 2.5 inches apart. This means I'd need a mirror
that is nearly 2 inches wide. That is certainly doable, but I've
never seen a helmet mounted mirror that wide. How wide is yours?

If you don't follow the math, here's a simple test. Hold your
fingers apart the width of your mirror. Move your hand to where
the mirror is located. Look at a distance object with one eye
closed, then the other. To be able to see both in the mirror
simultaneously, you need to be able to see the point with each
eye, through the window of your fingers. For the mirror widths
I'm familar with, that isn't possible.


Couldn't you just ask Sir to close the eye that's closest to the
mirror while trying to look at the mirror? If the view of the mirror
is blocked by Sir's nose, the mirror wont be in view.

Sir says he can see the mirror with both eyes, I've little reason to
doubt that. I've seen pictures of helmet mounted mirrors that project
far enough forward, past the front of the helmet, such that they would
indeed be visible with both eyes. That doesn't mean you can use them
with both eyes to see the same object, but maybe his is really wide.

The real question is whether there is anything in common between what
the left eye sees and what the right eye sees. Let him close one eye at
a time, while wearing the mirror, and report.

--

Sir Ridesalot writes:

On Thursday, October 30, 2014 6:32:36 PM UTC-4, JoeRiel wrote:
James writes:

On 31/10/14 02:14, Joe Riel wrote:


My eyes are about 2.5 inches apart. This means I'd need a mirror
that is nearly 2 inches wide. That is certainly doable, but I've
never seen a helmet mounted mirror that wide. How wide is yours?

If you don't follow the math, here's a simple test. Hold your
fingers apart the width of your mirror. Move your hand to where
the mirror is located. Look at a distance object with one eye
closed, then the other. To be able to see both in the mirror
simultaneously, you need to be able to see the point with each
eye, through the window of your fingers. For the mirror widths
I'm familar with, that isn't possible.


Couldn't you just ask Sir to close the eye that's closest to the
mirror while trying to look at the mirror? If the view of the mirror
is blocked by Sir's nose, the mirror wont be in view.

Sir says he can see the mirror with both eyes, I've little reason to
doubt that. I've seen pictures of helmet mounted mirrors that project
far enough forward, past the front of the helmet, such that they would
indeed be visible with both eyes. That doesn't mean you can use them
with both eyes to see the same object, but maybe his is really wide.

My immediate thought is that such a location might be less than ideal in
that it creates blind spots for both eyes, something not done with a
more rearward position.

--
Joe Riel

Easy enought to position the mirror so that it doesn't block forward vision to road/trail traffic. I can clesrly see what's in fronto of me.

My concern isn't with forward vision, per se, but rather blocking cars
coming from the left, the left cross. On my ride today, a knot head
driving a large SUV in the outside lane (I was in the bike lane) decided
to stop mid block (45 mph four lane road) to allow a car coming from the
other direction to attempt an illegal U-turn. Because of the SUV, I
didn't see the car turning until practically on top of it (despite two
lanes and a bike lane the car had to make and 3-point turn, stopping
in the bike lane), but had slowed when I noticed the SUV braking. For
stuff like that I'd prefer not to have any blind spots to the left.


--
Joe Riel