![]() ![]() When we try and take photos underwater, we have an additional medium to deal with, which affects the colour and intensity of light: water. Light is bouncing around all the time constantly having its colour, direction and intensity changed by anything it interacts with. Similarly the green light bouncing off the baize hits the red snooker ball which in turn absorbs the green light and any traces of blue light and again nothing perceivable is reflected. The red light bouncing off the snooker ball also hits the green baize, the baize absorbs the red and traces of blue light and nothing perceivable is reflected. The baize absorbs the red and blue light and reflects the remaining green light to our retina and we see the green baize. The same white light hits the green baize under the snooker ball. The red light hits our retina and we see a red snooker ball. The material of the ball absorbs blue and green light and reflects the remaining red light. There is no known material that reflects, refracts or absorbs 100% of light energy, there’s always some degree of reflection or absorption of light.Įvery time light bounces off something, the material of that “ something” absorbs some of the energy of the light affecting it’s colour and intensity.Ĭonsider white light hitting a red snooker ball. When it’s refracted, the light continues in a straight line, but its direction of travel has changed.When it’s absorbed, the light energy is convertedto a different sort of energy (i.e.When light is reflected, it bounces and travels in a straight line in a different direction.Light energy travels in a straight line until it’s reflected, refracted or absorbed (or any combination of the three). Incandescent filament bulbs produce warmer, more yellow light with a colour temperature of around 2,700 to 3,000 Kelvins. Fluorescent tube lights produce much cooler, “bluer” light with a temperature of 4,000 to 5000 Kelvins. The light emitted from the sun has roughly equal quantities of red, green and blue which results in white light with a colour temperature of between 5,000 to 6,000 Kelvins. Whereas paint colours are created by mixing the primary pigment colours: red, yellow and blue (sometimes called magenta, yellow and cyan), light colours are created by mixing the primary light colours: red, green and blue. It’s the same principle for film or a sensor in a camera.Įvery light source emits its energy at different wavelengths and therefore the colour of the light is different for every light source. ![]() Different proportions of different wavelengths are interpreted by our eyes as different colours. We have red, green and blue receptors (cones) on our retinas that detect these different wavelengths of light. These energy sources will invariably be radiating energy in lots of other wavelengths too (including gamma, x-ray, ultraviolet, thermal, infrared, microwave etc.), but its just the 400nm to 700nm wavelengths that our eyes can detect. The source of this energy could be a light bulb, the sun, a candle, a hot piece of metal, some uranium etc. Light is energy that has a wavelength between 400nm (nano-metres) and 700nm. Not all photographers use automatic settings and often isolate and manually set their ISO, shutter speed and aperture to get more creative control over their images. a wider aperture (which reduces depth of field making items in the extreme foreground or far background out of focus).ĭuring the day above water when there’s lots of light, a camera can be left on automatic and you’ll generally get a properly exposed image.a lower shutter speed (which can make the photos blurry due to camera shake).a higher ISO rating (increasing grain in the image).When there’s less light, the opposite needs to be set: a small aperture size (to increase the depth of field which makes more of the scene in focus).a high shutter speed (to freeze the action).a low ISO rating (to decrease grain in the image).When there’s lots of light a camera can be set with: Aperture: the size of the hole the light travels through towards the sensor.Shutter speed: the amount of time the film or sensor is exposed to light.For colour photography, in addition to receiving the right quantity of light, we also needs to capture light of the right colour.Ĭameras have three factors which control the quantity of light and how it’s detected: Overexposing an image will discard highlights in favour of bright white. Underexposing an image will discard shadows in favour of black. This means shadows are not too dark, highlights are not too bright and there’s a good distribution of light between those two extremes. The aim of taking a photo is to get enough light into the camera and detected by the film/sensor to produce a properly exposed image. Method 3: Use Photoshop’s new Match Color -> Neutralize functionĪll photography is dependant on one thing: light. ![]()
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