Color Temperature

In photography, what separates a Good and an Average photograph is the ability of photo to reflect the essence of light under which the photo was taken. The photo taken under different lightning conditions appears different and thereby losing it color identity. It is necessary to take into consideration the required white balance under different illuminated situations.
Visible light is the small fraction of the electro-magnetic spectrum between 400nm to 700nm. When white light is allowed to go through a dispersion element like grating or prism the light splits up into its constituent colors. Any object looks a particular color because it absorb all the wavelength falling on it and emit the remaining color. The object looks white when it reflects the full spectrum of light falling on it, so in situation when the incident spectrum lacks longer wavelength say Red, the object will appear slightly blue or cyan in color. Similarly when the object is illuminated with light deficient in Blue content the object will look slightly yellow tinted. As a result the object will lose it color contrast, even though it might capture other contrasting details.
Since human eye is adaptive the white object will appear white even in under slightly red or blue light. But in case of camera sensor this isn't the case as a result we need to secure white balance in order to retain the color contrast of the object. The origin of color contrast arises from the fact that when black metal object is heated it emits light such that the characteristics wavelength is proportional to the temperature it is heated. Upon heating the color the object changes from red, yellow white and then Blue. The temperature is measured in Kelvin and is called the color temperature of the source. The object when heated to 3600 K emits Yellow light, so the light that emits is said to have a color temperature of 3600 K. If we heat the object to 5600 K, it has a spectral distribution similar to that of normal day light at Noon. So the candle light has a color temperature of 1900 K, Normal Tungsten lamp 2800 K, Flash light 5600 K, and a blue sky has 10000K. It is necessary to adjust the camera white balance setting in order to match the color setting of the illuminated source.
Thus before taking any photography make sure you set your appropriate white balance on your setting such that you dont end up losing the color contrast of your image to repent later.

Human Eyes and Camera.

Photography is a photophysical process, where the photon interact with the matter and then carry relevant details along with emotion and time to the viewer. Photography freezes time, and let you revisit your past.It's a wonderful science that has come into origin ever since man has understood the working of human eyes.The working principle of camera and human eye are same. But the technical capabilities that human eyes poses that is an outcome of million year of evolution is far greater than camera that has its origin for just close to a century.
Photography is an outcome of light from source being reflected/diffused or scattered from object that reaches the detector/films. Where else Vision is a result of interaction between human eye and adaptive image recognition undertaken by brain, which makes it the most complicated image sensing device that can be ever thought of.
Human eye as seen from the figure has a lens which undergo contraction and expansion through iris, thereby changing its focal length. The iris diaphragm opens wider for faint light and closes down in case of bright light. The lens is immersed in between 2 fluids referred to as Aqueous humor and Vitreous humor having refractive index of 1.336 and . The size of human pupil varies between 2mm to 7mm. The lens from the image on the retina which contains photoreceptors Rods & Cones which convert the photon energy into electrical signal that is interpreted by the brain as image. Rods are responsible for intensity detection and Cones are color sensitive. There are 3 types of cones sensitive to blue, green and red part of the visible spectrum. Cones are responsible for vision during day, and rods during night time. We have around 120-130 million of cones and around 10 million rod on our retina. Considering a large field of view human eye has a resolution of close to 500 Megapixel. In a single view Eye can detect contrast change of 10,000 ie it can function normally under bright sunlight as well as dim faint star light. Where else the eyes focal length is around 22mm. These are the technical details associated with human eyes which surpass every camera specification we can ever think of.
But there are few specification that camera poses over which has great advantage over human eye. The photoreceptors in eyes has a temporal resolution of around 1/20 sec, for any motion greater than this time scale eyes see it as continues vision. Where else in camera we can play with shutter speed for time upto to 1/8000 sec under sufficient illumination and captures images which can never be imagined. Something like bullet through soft material. And also we can have long exposure on camera to have drastic effect which human eyes is incapable of achieving. Since human eye combines images formed every moment, its not possible to have certain effect like long exposure scene through human vision.
Nevertheless human eye if properly understood it can result in awesome shot being taken. Simple adaptive optics associated with eye and human brain forms the best imaging device.

Introduction.

This is an attempt by me as a Physics Graduate to explain the intricacies and details about photography, that I have learned over the time. Photography wasn't my passion, until I happen to visit a place with my friends and someone took stunning photo's with simple mobile and point and shoot camera. It was then that I became passionate about taking photos. As an early attempt I purchased a SONY H9 DSLR type camera and later upgraded to Canon EOS 450D.
Over the days I have learned a lot of photography and wish to share it with my friends about how photography can be understood but with a technical flair added to creativity.
It will be my attempt to simply the physical jargons of physics show how they can be correlated to creative photos.
Photography is all about PHYSICS, but taking good photo is an ART. Well my attempt is to unravel the science and learn the art.