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Old August 4th 15, 05:10 PM posted to rec.bicycles.misc
Frank Krygowski[_4_]
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Posts: 10,538
Default AG: Safety Equipment for Bicycles

On 8/3/2015 9:07 PM, John B. Slocomb wrote:
On Mon, 3 Aug 2015 11:00:36 -0400, Frank Krygowski
wrote:

On 8/3/2015 7:58 AM, John B. Slocomb wrote:
On Sun, 2 Aug 2015 11:43:05 -0400, Frank Krygowski
wrote:

FWIW, I find eyeglass-mounted mirrors to be much superior to helmet
mounted ones. Positional stability is better, ease of attachment is
greater, and of course it works with any (or no) hat. And as a little
detail, I can even use it flat-water kayaking, to make sure my wife
doesn't get too far behind in her boat.

And isn't it interesting that helmets are still number one the minds of
Americans in the "bike safety" category? Have you ever been
complimented for obeying the rules of the road? For bicycling only when
sober? For properly choosing your lane position? Probably not.

But a funny hat intended to prevent the 0.6% of the brain injury
fatalities in America that occur while cycling? Oh, gosh, that's very
important.

Out of curiosity do you wear glasses? I ask as I tried a helmet
mounted mirror to see whether I wanted to use one and it almost drove
me crazy. I wear bifocals and the mirror was "above level", if that is
the right description, and when I looked at it, it was through the
upper, "long range" part of my glasses. Couldn't see anything but a
blur. tipping my head back to use the lower part of my glasses didn't
work either as, of course, when I tipped my head back the mirror went
up too :-)


Yes, I do wear glasses, which is one of the reasons I like
glasses-mounted mirrors. Instead of standard bifocals, mine are
"blended" bifocals.

I don't understand your problem, though. I position my mirror so it's
visible through the top left corner of the glasses lens. That's in the
"distant focused" portion, so it works perfectly for viewing the image
of a car or other cyclist who's a long distance away. Remember, you're
not focusing on the mirror itself, but on the image in the distance.

If the mirror were visible only through the "close focus" portion of the
bifocals, there would be a problem; but that's not the case.


It must be my eyes than as I just tried out your theory with as hand
mirror and there is a distinct difference in how clearly I see the
reflected image in the mirror when I look through the top or bottom
portion of my glasses and that difference also varies depending on how
far the mirror is from my eye.


Sure. Looking through an ordinary flat mirror is no different than
looking through (say) a hole in a fence. If you were trying to peek
through a fence to see a distant object, you wouldn't use the close
focus part of your bifocals.

It is also apparent that different mirrors have a different focal
length or whatever as if I look the central "inside" mirror in the
truck I get a different prospective than when I look in the "wing"
mirrors with both mirrors are essentially the same distance from my
eye. In the wing mirrors the object appears to be much further away
than the inside mirror shows.


Yep, some external auto & truck mirrors are convex. So are some
handlebar mounted mirrors for bikes. Convex mirrors gain a wider field
of view and, on bikes, a little less sensitivity to vibration. Convex
mirrors make it a bit more difficult to judge distance, hence the
warnings on some of them that "objects may be closer..."

AFAIK, all eyeglass mirrors are flat, not convex. They don't need the
wider field of view, because one can pivot one's head to scan a wide
area behind.

I have the suspicion that a glasses ort helmet mounted mirror is a bit
more complex than "just stick a mirror on there".


The mechanical and optical parts are not complex at all. (I make my own
eyeglass mirrors; it's pretty easy.) But some people have trouble
learning to use them.

I've read that for some folks, problems may be caused by extra-strong
eye dominance. I'm right eye dominant, but have my mirror on my left
glasses temple. I eventually realized I blink every time I turn my
attention to the mirror. Perhaps that gives a useful disconnect,
allowing re-focusing my attention.

Some people are bothered by the mirror obstructing a bit of the
forward-sideward field of view. I make my mirrors small and as close to
my eye as practical (maybe 2" away) and mount them so they're as high
and as far leftward as possible. There's effectively no blind spot,
because my dominant right eye covers that part of my field of vision.

But this might not work for everybody.


--
- Frank Krygowski
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