Commit This to Memory

Exercise 1: How does ‘the world’ change as the light changes? 18/40 marks
Approx 1000 words (not including your notes, which are to be handed in with the essay)

The perception of the world depends on the light source, the properties of the illuminated surface and, at the outset, the sensitivity of the photoreceptor mosaic on the retina. This mosaic is made up of three cone-types (L, M and S- wavelength sensitive) and one type of rod. Not only do these four photoreceptors have different spectral (wavelength) sensitivity but they also have different brightness sensitivity such that in under moderate to bright light-conditions, rod output is completely saturated and only cones contribute to your visual world. As the light level drops, then the effective contribution of the cones becomes less and the rod contribution to your vision increases until, at very low light levels such as moonlight, only rods mediate your vision. Observation of these two extremes and the transition between the two provides an important insight into the constraints placed upon the whole visual system by the ‘front end’.

What I would like you to do is to take notes on the apparent change in your percept of the world as you move from cone- to rod-mediated vision and describe this change.

You are to sit outside, as far away from artificial light sources as possible, at sunset(or if you are really enthusiastic – at sunrise) and record the changes in the visual image as the light level falls to darkness. If you can choose a clear moonlit night then the experience will be much richer. Then use your notes to reflect upon the change and the insight you have gained from it. Consider the change in appearance of the colour, the form, the depth, the motion in the environment and relate this to what you know about the early processes of vision. It is most important, however, for you to reflect upon your observations and thoughts rather than give me some specific answer.

Sigh, I need some help here.

Shall go and revise some psychology.........haven't touched it since week one, unless attending lectures are counted.

But everyone knows you don't really learn much in lectures....right?

Who wants to sit and watch the sunset with me and take some notes? I know, far out...it's freezing these days.

I'm feeling a terrible lack of motivation tonight, basically, I feel very tired.

love, 21:23
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