This was to establish the minimum percentage polarisation at which Haidinger’s brushes could be detected. Among 24 people, the average polarisation sensitivity threshold was 56%. Some people could still see Haidinger’s brushes when the light was less than 25% polarised – not quite as good as cuttlefish but still better than any other vertebrates tested to date.

There is a tendency to rely on digital cameras’ built-in meter, and while they are far more accurate than they used to be, many photographers could still benefit from the increased accuracy and reliability of using a dedicated light meter. Sekonik is the de-facto name associated with accurate light metering and we provide a comprehensive range of their products, including grey cards and profile targets. Read the guide to using a light meter on the Exposure Guide website, which will help understand the basics if you are just starting out.

For studio photography light meters are essential as they guide photographers as to which settings their cameras and studio lights should be at. However many outdoor photographers also use a light meter to gauge fast changing scenes, capture accurate white balance and expose for the highlights. Meters are ideal when using a filter system such as LEE as the bright sky and dark ground can be independently metered, helping to decide on which ND graduated filter which will be required.

The ability to see Haidinger’s brushes is caused by circularly symmetric organisation of carotenoid pigments in the macula (an area that covers and protects the central part of the retina). Blue light which is oscillating parallel to these pigment molecules is strongly absorbed. White light, which is depleted in blue, appears yellow, which explains the yellow bow-tie effect. The blue parts of the brushes are thought to be generated by the brain in response to the unexpected presence of yellow.

Skylight polarisation patterns, caused by light scattering in the atmosphere, are such that the long axis of the yellow bow-tie will point approximately towards the sun.

You will probably have come across technology that is built around polarised light before. For example, “Polaroid” sunglasses work by blocking out polarised light which is reflected from shiny surfaces such as car bonnets or the surface of water. This is possible because light reflected into our eyes from horizontal surfaces is horizontally polarised and the sunglasses have a structure like a picket fence, so they only let in vertically polarised oscillations, blocking out the horizontally polarised bright reflections. Polarised light is at the heart of modern 3D cinema and LCD computer screens, smart phones and tablets.

A light meter offers a reading based on grey point, which is how an internal camera meter also works.It will not only provide the correct exposure, but also save time as photographer will get the exposure correct the first time rather than through trial and error.

In research we’ve just published in Proceedings of the Royal Society B, we used an experiment that was originally designed to test the visual abilities of octopuses and cuttlefish to investigate our human ability to perceive this polarised light.

In previous studies LCD screens have been used to test polarisation sensitivity in aquatic organisms. Our study tested the limits of human polarisation sensitivity, developing special filters to vary the percentage of polarised light reaching the eye from 0% to 100%.

As AMD is currently the leading cause of blindness in the developed world and finding an early stage diagnostic indicator of this before any actual sight loss is incurred is a research priority. It is our hope that polarisation sensitivity could be used to investigate and ultimately monitor any changes in the organisation of the pigments happening in the early stages of this degenerative eye condition. More work is needed to assess the medical potential of these kinds of tests.

© 2024 Park Cameras, York Road, Burgess Hill, West Sussex, RH15 9TT | VAT No. GB 315 9441 58 | Registered Company No. 1449928

Technical specifications are for guidance only and cannot be guaranteed accurate. All offers subject to availability and while stocks last. Errors and omissions excepted. Registered Company No. 1449928. Park Cameras Limited is a credit broker, not a lender and is authorised and regulated by the Financial Conduct Authority (FRN 680161). We do not charge you for credit broking services. We will introduce you exclusively to Omni Capital finance products provided by Omni Capital Retail Finance Ltd.

So if polarised light is actually pretty common outdoors, in your home and in your office – how come you didn’t notice anything special before now?

Whether checking ambient or flashgun light, inside a studio or outdoors in natural light, whether using incident or reflected metering, there is a wide selection of light meters available at Park Cameras for photographers of any experience level.

A camera light meter provides an exact exposure measurement, informing the photographer of precisely what shutter speed and aperture they should use for any given scene. Employed by studio, portrait, product and fashion photographers, many beginners and enthusiasts are missing out on this essential piece of hand-held equipment. They are crucial for some, yet are often forgotten for others shooting digitally, but can make the difference between a professional looking or average image.

We are all familiar with colour and brightness, but there is a third property of light – the “polarisation” that tells us the orientation in which light waves are oscillating. Animals, like bees and ants, use the polarisation patterns in the sky as a navigation aid. But few people, even in the scientific community, are aware that humans can perceive the polarisation of light with the naked eye.

Fast and easy trade in service ensures your old gear is collected efficiently and you are paid quickly! It's very simple to trade in your unwanted photography gear. Just head over to our dedicated Sell or Part Exchange page, fill out the details, and we'll get back to you with an offer for your old gear. Take the cash, or put it towards the cost of your new gear. It's up to you! Find out more

Imagine a skipping rope is a light wave travelling through space. If you move the rope from side to side, the wave you make is horizontally polarised. But if you shake it up and down you create a vertically polarised wave. Generally, light is a mixture of polarisations, but sometimes – for example in parts of the sky, on your computer screen and in reflections from water or glass – a large percentage of the waves are oscillating in the same orientation. This light is described as being strongly polarised.

By using LCD screens capable of constantly refreshing the effect, we were able to make the first measurements of the dynamics of Haidinger’s brushes, confirming the prediction that some individuals would perceive the orientation of the bow-tie to “flip-flop” as the polarisation angle is rotated.

Haidinger’s brushes also provide a demonstration of the physics of light and the anatomy of the human eye. By taking the polaroid layer off an old LCD screen you can make your own simplified version of our test; black and white letters turn into contrasting polarisation angles once the polarising film is removed.

At a recent science festival I tried to get people to take an “octopus eye test” by reading the hidden letters using their polarisation sensitivity alone. It went down a storm, except with one little boy, who was terrified of the accompanying octopus headdress. Time to work on a less intimidating super-costume.

To see Haidinger’s brushes for yourself, look at a blank white portion of an LCD screen on a computer, tablet or phone. Tilt your head from side to side and faint yellow and blue bow-ties, slightly larger than your thumb, should become visible. With practice, you can then see them in the blue parts of the sky at 90 degrees from the sun, particularly at sunrise and sunset.

Juliette McGregor does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Might it be possible to use our polarisation powers for good? The risk of acquiring age-related macular degeneration has previously been associated with low carotenoid pigment density in the macula.

Humans perceive polarised light using “Haidinger’s brushes”, a subtle visual effect which appears like a yellow bow-tie at right angles to the polarisation angle. You may also see a bluish bow-tie at right angles to the yellow one. The effect originates within the eye itself and is not an image of a real external object, so Haidinger’s brushes usually fade in a couple of seconds as your brain processes them out. This is one of the reasons that few people notice them day-to-day, and why they have previously been fairly difficult to study.

Our results shows that your cornea can dramatically affect how you perceive polarised light. As the optical properties of the cornea vary between individuals, this may also explain why people often report their experience of seeing Haidinger’s brushes differently.

Ever fancied having a superpower? Something you can call upon when you need it, to hand you extra information about the world? OK, it’s not X-ray vision, but your eyes do have abilities that you might not be aware of.