Your web site looks good, it has a great design and you getting more and more viewers: it's a success! But there is a snag: the colors of your photos are way off, too yellow or too blue! You have virtually no experience in Photoshop or Gimp, this problem is barely remediable even if you has a lot of time to solve it.

Luckily for you there are several solutions: 1 - never post pictures on your site; 2 - buy a bigger camera, 3 - ask one of your friends to correct the pictures because you are can't do it, 4 - learn a basic rule which gives good results.

• 1 - at your own risk: the web is now content rich, and it is going to be really hard to retain a viewership if all you are displaying is long walls of text. You need texts of course but it will be way more viewer friendly if you can complete them with pictures.

• 2 - This is a good excuse to buy yourself the even-more-recent model than the one you bought three months ago, which was even better than the one from six months ago, which was ... and your pictures colors are still way off! Unfortunately for you this kind of strategy won't get you anywhere, especially because when the camera is better, it is more complex. If you persist in this way, it probably means you have lots of money.

• 3 - This is a good solution if you have the right kind of friends: the selling point is that you no longer have to worry about your pictures, you are not the one doing the actual work, the photos are beautiful ... The problem is that you need a friend always available, or a second friend to take over, your styles might mismatch...

• 4 - It may be your last chance to improve the quality of your images. Yet this is what we might call the choice of reason: with an easy learning curve you gain knowledge that will allow you to save valuable time while improving the quality of your pictures. This is a good investment to ensure the well-being of your website.

A bit of scientific background about light: (abbreviated nm = nano meters; CT = color temperature)

The light seen by the human eye consists of a set of wavelengths from approximately 380nm (violet) to 780nm (Red) through green at 600nm.

We can approximate this spectrum by a set of red, green and blue additive colors, the addition of the three giving white and the absence of the three giving black (not to be confused with painting colors where the colors are substractive). 

Daylight varies in its composition during the day. However we consider that it is 5500K. For heating a theoretical black body at the same temperature yields a light of about the same spectral composition. The spectral composition of light depends on the temperature and the composition of the element that illuminates. Overall light whose color temperature is below 5500K is called "Warm" because it will be more red to the eye and a light whose temperature is higher than 5500K will be called "cold" because the eye will see it more blue. The automatic setup of most cameras balance your photos using this reference value by default. Your pictures will then be more orange if the color temperature is lower and more blue if it is higher. Depending on your model, you can help your camera choosing the right reference by setting the reference temperature explicitly, or by identifying the approximate type of lighting, for example, "cloudy" or "electric light". Obviously a device for measuring  color temperature (a color temperature meter) is expensive and doing an approximation yourself can give good results. Here are some examples as a reference.

2000K: Sun on the horizon in the evening

2800K: Conventional incandescent 100W lightbulb

3200K: Halogen Lamp

5500K: Sunlight, at noon

6500K: Sunlight but in the shade

There are special cases because the spectral composition of these sources are continuous, ie it changes from red to blue along a continuous spectrum of wavelengths. Now lights called "fluorescent" as "neon" and energy-saving lightbulbs have a discrete spectrum with peaks. For this reason in those cases you should trust your camera and select a "Neon" setting as choosing the color temperature directly will not really lead to good results. In the case of very detailed pictures, it is a good idea to adjust the white by hand.

Telling your camera the color of ambient light is called adjusting the white-balance. Your camera then knows which objects should be white as a paper sheet, when it would make them appear orange under "warm" light without white balance adjustment.