Posts tagged ‘sight’

Your Eyes Adapt to Darkness In 20-30 Minutes

If you’ve shopped for an HDTV, you’ve probably seen something on the spec sheet called “contrast ratio.” Contrast ratio is the difference between the darkest and brightest picture a TV can produce. Contrast is important to a good picture.

That’s because our eyes can recognize a contrast difference of 1,000,000,000:1. That means, the brightest thing our eyes can see is a billion times brighter than the darkest thing. Good contrast to your eyes is like a gourmet meal for your taste buds. Contrast adds a lot of detail to the picture and ultimately immerses you in the action.

Unfortunately, when shopping for TVs, contrast ratio is almost meaningless. It could be really useful, but all of the manufacturers measure this number differently and then call it the same thing — it’s really only useful when comparing two TVs from the same manufacturer.

Imagine you want to buy a new car: you are cross shopping three manufacturers who measure fuel economy in three different ways. The first one, measures fuel economy while driving down a hill, while the other two measure it on flat land and while driving up a hill. Obviously, you can’t compare the results of those tests. But, if you’re looking at two cars from the same manufacturer then there is some comparative value to those numbers, even though they may not be accurate in a typical situation.

Thankfully, our eyes are extremely sensitive to contrast. Turn both TVs on and look at a flat black image for a while. A flat black image makes it easy to spot variations in darkness (aka “banding”), no banding should be present in a good TV. If you still can’t tell the difference and they both look good, then the difference is too small to worry about. Trust your eyes, they are incredible instruments.

It takes 20-30 minutes for your eyes to adjust from one extreme to the other because the contrast ratio is so high. If you’re in bright sunlight and then walk into a very dark room, it will take 20-30 minutes before you can see your best in that room. If you are in a moderately bright room and go into a very dark room, it is often closer to 15 minutes.

The rods and cones in your eye are tested during dark adaptation. Rods are more sensitive to light and take longer to adjust. Cones are much faster to adjust, often in approximately 9 minutes. People over the age of 50 need twice as much light to see as well in the dark as a 30 year old. So, if you need more light, consider my CF light secret.

Frequent fliers will eventually notice that the aircrew dims the airplane’s interior lights on final approach during night landings . They want your eyes to be adjusted to the darkness outside in case the landing does not go as expected and you have to evacuate the plane.

Broken Secrets

Written By: Chad Upton

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Sources: Why Planes Dim Interior Lights, Adaptation (Eye), Contrast Ratio, Growing Older

January 22, 2010 at 1:10 am 1 comment

Colored Sunglass Lenses Can Improve Your Sight

Let me be clear, they don’t improve the focusing power of your eyes but they can change the way things look so you recognize them more easily. That’s important when reaction time is critical.

Yellow lenses are a popular option but it’s a myth that they make things brighter — they do not amplify light. But, according to the American Academy of Ophthalmology, they do enhance depth perception. This is because they block some of the blue light that can make objects look hazy and reduce sharpness.

For this reason, yellow lenses are popular with pilots, cyclists, shooters and boaters in low light. In daylight, blue lenses are good for pilots and skiers because they enhance the contrast between objects that are white (snow and clouds) and other objects. For boaters, red lens are good because they increase the contrast between water and objects that are in the water.

Although colored lenses can increase contrast in specific conditions, the downside with any colored lens is that they obviously distort color. Brown colored lenses are the happy-medium; they offer minimal color distortion while improving contrast, so they’re great for everyday use.

BrokenSecrets.com

Big thanks to Todd for sharing this secret with me!

Sources: American Academy of Ophthalmology (PDF)

January 7, 2010 at 12:40 am Leave a comment


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