Different perception of monochrome and colour

Last Tuesday, I was at a meeting of my local camera club down in Maidenhead and they had a talk by Micki Aston & Rod Bird about monochrome photography.. They were talking about the way that some images are better suited to monochrome and how monochrome enhances texture.

I tripped over that thought. Because in my experience, it is absolutely true. It is a statement based in fact and evidence, not some wishy-washy arty assertion: I find that I absolutely percieve texture much more clearly in monochrome than I do in colour.

And I started wondering about why this might be the case. The retina at the back of your eye contains two different types of cells, which detect light. Cones and rods. They work completely differently. They have different distributions, different sensitivities, they respond to different things. It is asif you have two completely different sensors at the back of your eye, working in parallel.

The cones detect colour. They are concentrated in the middle of the retina in an area called the macula. You have around 6 or 7 million of them. A 7 megapixel sensor if you like. The cones are not particularly sensitive to light. They need decent levels of light to work properly.

The rods detect brightness. They are much more sensitive. Around 1000 times more sensitive than the cones. That's 10 stops in photographic terms. It is reported that in ideal conditions (after spending half an hour in absolute darkness), a rod cell will respond to a single photon of light. The rods give us our night vision. There are around 120 million of them but they are spread all round the retina and so are packed less densely than the colour cones..

So, where is this taking us?

I think that it might be the reason why we percieve black and white images differently to colour. If there is no colour, then perhaps the brain, which processes the signal from the cells switches from using the cones to the rods. So rather than being swamped with coilour information, the visual processing centers of the brain concentrate primarily on the tonal information provided by the rods.

I think that we might percieve black and white photography differently because we might use our eyes in a completely different way when we look at them, using promarily the super-sensitive rods to detect texture rather than the cones that we would normaly use for high resolution perception in good lighting.

I am not an ophthalmologist. I have no training in this area. This is only guesswork on my part. I would appreciate feedback from folk that actually know what they are talking about :-).