On Wed, 20 Nov 2019 14:47:44 +0000 (GMT), "Dave Liquorice"
wrote:
snip

Which in the case of star or moon light it is. It's our eyes that
can't work in colour at low light levels and transition from using
the cones (colour) to rods (monochrome).

Clever aren't we, how we have evolved such things. ;-)

Also bear in mind that the
central area of our vision is exclusively cones

I've had experience of that going a bit wrong when I had what I think
they described as some 'wet' distortion of the macular in one eye
making square things look distorted and creating what looked like a
oil stain on anything I was reading (that wouldn't wipe off and moved
when I looked elsewhere). ;-)

Luckily, it cleared up on it's own and if it hadn't, any (laser?)
surgery I could have had on it would have left permanent distortion
(in my main focal function in that eye).

so if you want to see
something in low light levels don't look directly at it but 15 to 20
degress away so the image is formed on the retina where the maximum
number of rods are.

Cool. ;-)

It's this sort of 'human' thing I was talking about in another group
regarding the proliferation of what many of us would describe as
'overbright' vehicle headlights.

In the old days, the light levels projected and visible were directly
related to the wattage of the lamps used and hence the wattage limit /
restrictions. Yes, upgrading your headlamp bulbs to something more
powerful might make things better for you but not anyone else
(especially those swept by them on corners and on roundabouts etc,
even if they were properly aligned / focused).

Eg, we (humans) have a tolerance to a range of light levels, from
pretty dark to a bright sunny day and we can generally cope with them
all (by looking away from the sun etc) but we don't generally have the
same option when driving.

And it's not just the light levels, but the colour temperature and
density of a source that can make a big difference as well (LED /
laser V an incandescent filament). You get bright lights at a football
match for example but they aren't painful to look at.

Cheers T i m