Watching the World

SnowSceneS

Garden, under snow, in the dark. Taken at 11p.m.!



2009 saw a lot of snow in Southern England. I found myself wondering: what does it look like in the dark?

Thanks to the miracle of long exposure (and a tripod!) I found out.

It shows a combination of the cleverness and the flaws in human vision. The snow shown here is stained with the orange light of sodium street-lighting, but the colour is not apparent to the human viewer because we correct for it. (Of course, I don't know how much of the colour cast is due to reciprocity failure, but I suspect very little due to auto white-balance.)

The human eye has two types of cell in the retina, equivalent to the receptors in a camera's sensor. The "yellow spot" (fovea) in the centre has 95% of the colour receptors (cones) but covers only 2% of our vision. This gives very detailed colour vision, but has a slow response time. The remainder is made up of rods, simpler cells with a fast reponse that only respond to brightness, giving a monochrome image.

On the other hand the camera picks up much more detail by collecting light for a long period. We can't do this, but even if we could it wouldn't be very useful because you'd have to stand totally still and stare at the view, or everything would smear like a video effect. We benefit from having less detailed "real-time" night vision because we can detect moving objects, or see where we're going when we move, much more easily. A worthwhile trade-off?

SnowScene 2

Garden, under snow, in the dark. Different view a year later.



And in 2010 . . . I did it again. We've had white street lights fitted on one side, so the orange is less strong in the sky.

Email opal @ opticalallusion.co.uk

Hastings Pier.

Last Poppy.

Poppies.

Church Tower.

Last of the Summer (whine).

Spear of Destiny.

Among the Ruins.

Along Came A Spider.

DewDrops.

Gone Fishin'.

Oases of Light.

The Harveys Brewery.

The Grangel.

SnowScene.

Sunset on Trees.

Average Sized Redwood?

Dark skies.


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