Re: Battery/lighting philosophy for fully-loaded touring?

In article <slrnf23ria.7bg.spamspam@xxxxxxxxxxxxxxxxx>,
Ben C <spamspam@xxxxxxxxx> wrote:

On 2007-04-14, Tim McNamara <timmcn@xxxxxxxxxxxxx> wrote:
In article <slrnf212uq.7bg.spamspam@xxxxxxxxxxxxxxxxx>,
Ben C <spamspam@xxxxxxxxx> wrote:

On 2007-04-14, <josh@xxxxxxxxx> <josh@xxxxxxxxx> wrote:
In article <462013d7$0$27192$742ec2ed@xxxxxxxxxxxxxx>,
scharf.steven@xxxxxxxxxxx says...
Andrew Price wrote:

Really? What on earth does the amount of load on the bike have
to do with the rider's ability to see with the light provided by
the dynamo?

It's not the load, it's where you're likely to be riding on a
tour. If you do your tours in urban areas with bright city lights,
then you could probably get by with a dynamo. Most people tend to
do their touring in more rural settings.

In more rural settings, without the glare of street lights and with
less oncoming traffic, bright lights are less useful than in the
city where you need to bring up road details against a bright
background. I often enjoy riding without lights in rural areas,
other than a tail light and a minimal front light so I can be seen.

You must eat a lot of carrots. I have a real problem seeing where I'm
going in those conditions unless it's a full moon.

[...]
The other criticism I have of battery powered lights is physiological.
Really bright lights (especially mounted high) result in a lot of light
bouncing back from near objects which can reduce dark adaptation of the
eye. It takes about 45 minutes for the retina to become fully dark
adapted, and light interferes with this.

Where I live you'd be very lucky to go for as long as 45 minutes without
being dazzled by a car coming the other way.

There is a theory that you can shut one eye when that happens to keep
that eye dark-adapted. Not sure how effective that is, or what your
liver would make of the situation re rhodopsin shunting.

It works if you can keep all the light out. How much
gets through the tissue of the eyelid? Mythbusters
tested the myth that sailers wore an eye patch to keep
one eye dark adapted for descending to the lower decks
that were very dim. Their result showed that an eye
kept under a patch remains dark adapted in full sun light.

The full dark adaptation process is forced at the
retina. Build up of all-trans-retinal from the reaction
of rhodopsin with light reacts in the retina to form
all-trans-vitamin A which builds up in the blood stream
and in the liver where we have

all-trans-vitamin A --> II-cis-vitamin A

and the latter is carried back to the eye where it is
further processed and is recombined with optin to form
rhodoptin.

Bright light on the retina quenches this reaction chain
by removing the forcing population of all-trans-retinal.

--
Michael Press
.

Relevant Pages

  • Re: Battery/lighting philosophy for fully-loaded touring?
    ... Really bright lights result in a lot of light ... It takes about 45 minutes for the retina to become fully dark ... There is a theory that you can shut one eye when that happens to keep ... liver would make of the situation re rhodopsin shunting. ...
    (rec.bicycles.tech)
  • Re: Dark adaptation on exit pupil size
    ... dark adaptation is primarily a chemical process within the eye. ... > fraction of the total improved light sensitivity of the dark adapted eye. ... > not aware of research showing a correlation between pupil size and naked eye ... eye is in the retina, ...
    (sci.astro.amateur)
  • Dark adaption and pupil size - an experiment (longish)
    ... when I was about six years old looking though a neighbors reflector ... The 11x80 bincos were very impressive from a dark ... I'd do an interesting experiment to see if increasing my pupil size ... often used in eye drop form by eye doctors to dilate patients ...
    (sci.astro.amateur)
  • Re: Scotoma was The Actual Data about the Relationship of Tight Control & Retinopathy
    ... bits of the retina. ... thought I was losing the sight of that eye. ... If these change it will take time for the aqueous humour to settle ... That's proliferative retinopathy. ...
    (alt.support.diabetes)
  • Eye Update
    ... For those who were paying attention the first time around... ... because the retina guy didn't like some stuff he saw in the optic ... When the glaucoma lady first looked at my eye, ... vision of an 18 year old. ...
    (rec.games.computer.ultima.dragons)
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