The Stilling of Movement

June 14, 2010

Just to add to a previous post about a star trail photograph I took, where I mentioned the way that long and short exposures can bring about a different sort of image than the one we see with our eyes. I said that our perception seems to work on a 1/20 second time lag, and that is why moving pictures work with just over 20 frames per second. I used the example of a waterfall photograph, but without an example to hand.

Well, last weekend Crafthole & I found ourselves looking at a weir and I thought I’d use it to qualify my statement. This is a 1/20 second  exposure, which freezes the image exactly as it is seen in the real world:

Any shorter and moving water becomes an unnatural sight to our eyes (this is 1/200 second)

And any longer and the chinks of light merge together into seamless milky-whiteness (1/2 second)

This is not a photography post, more of a note on human perception of movement. I say human because we are all wired differently: insects have very short connections from sense to brain and so have faster sensory turnover than we do (or a faster inherent shutter speed; I like that thought): a 24 frame per second movie would not create the illusion of movement for a fly, and presumably falling water looks to them like my 1/200 second photograph. Dogs however, see it just as we do. It’s all about scale. Time really is relative… *scratches head and furrows brow*


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