White Balance

Why is White Balance so Important?

To become a good photographer, I believe you have to master aspects like Exposure and White Balance. Not only master the techniques but also to develop a good understanding of these aspects are critically important. On the other hand, it is only when you develop a good sense for quality of light, light temperature and white balance, that you will be able to really master exposure.

Spend a few minutes to study this article, do your best to create a picture in your mind of what is discussed here and you will most definitely improve your ability to take good pictures.

What does the picture on the sensor look like?

The picture that is captured on the sensor or the old 35 mm film strip is a Black & White picture.

This is one of the most important aspect of photography to understand. The digital camera has a color (RGB) filter placed above the sensor. The incoming light (picture) is filtered and only the remaining black and white picture is captured by the sensor.

To complete the captured picture, a copy of the RGB filter values is added to the captured picture plus the white balance value in Kelvin, of the camera.

How does one recreate the color picture?

In layman’s terms, the process is very simple. All that is required is to take the same RGB color filter and to add the measured color temperature to that and to pass the black and white picture back through the RGB color filter. On the other side we will have the original color picture.

The problem is that the moment the picture is saved on the sensor it is not any longer a picture, it is now a digital file and a digital file cannot be send back through the RGB filter.

What we can do is to simulate the original RGB color filter in the camera processor. Then to add the white balance value and finally to calculate the original color picture. That is exactly what happens in the camera or alternatively in a RAW converter on your PC. This is a highly specialized process and that is why we see camera processor names like Dicig or Truepic. These are the special in-camera processors that will rebuild the color picture.

What is interesting is that the JPEG color file that is saved by the camera has a similar file size as the RAW picture that is still in its black and white format. In other words, the color picture has the same amount of bytes saved between the 3 RGB colors. The RAW file has all the bytes saved only in the black and white picture. The black and white picture will then be converted for each of the RGB colors in the PC. That is one of the reasons for a RAW file containing more information.

If you therefor selected the RAW option, then the camera will also take the sensor (Black & White) file, which is called the RAW file, plus the RGB values and the white balance value and this will be saved as one RAW file.

To Summarize why WB is so important:

The only variable, the camera does not have an exactly value off, is the white balance value. The camera does have the black and white picture saved on the sensor plus it has the precise values of the RGB filter. The only area therefore open for mistakes is the white balance.

Many people say, but that’s easy, just use RAW files and then you have access to the white balance setting in the software. This is one of the biggest misperceptions found in digital photography today. To explain this, I like you to go outside and to estimate the color temperature.


	To explain the above question in a little more detail. If you have to estimate the outside color temperature then it can be anything from 4000K right up to 8000K depending on what the conditions are. Are you standing in the shade, is it over casted, is it early morning or late afternoon, any of these will have a different color temperature.

What happens if we use a incorrect white balance value?

A incorrect white balance value will result in the picture having a color cast. What is the difference between white balance and color temperature? It is the same thing, color temperature is expressed as a white balance value.

Sometimes photographers purposely use a different or incorrect white balance value because they purposely want to create a color cast. For example a photographer could decide to use the “clouds” white balance setting for a landscape picture. That will have the same effect as a warming filter.

How can we measure white balance accurately?

Using a gray card is the most effective way of getting the white balance right. Both the G7 and the Oly allow the photographer to enter a custom white balance. Typically a SLR will go one step further and it will allow the user to fine tune the white balance.

Personally my advice is to practice using a gray card, especially if you enjoy capturing the ambiance of a specific situation. Settings like late afternoon sun beams and color effects, different exposure and lighting effects inside a room and so much more.

Typically the digital camera is highly advanced and in most cases the auto white balance will do a good job of setting the white balance. Similar to noise, this discussion is aimed at that last 10% of taking the perfect picture. In 90% of all your pictures, everything will be OK. Its when you faced with unique sunsets for example that knowing and understanding how to use the gray card will help you to capture beautiful master pieces. Also people wanting to get the picture right in the camera will typically learn to master using a gray card.




			The above series of pictures are straight from the camera and not post processed. All used auto white balance. As you will see on all the different pictures, the color of the house is different. Is that the way our eyes see the house in different weather conditions? No, we always see white as white, does not make a difference if we inside the building, outside the building or in bad weather. How can we help the camera to see it the same way as we do. Use a gray card... Kind Regards Siegfried

	Letter from one of the readers on White Balance.... Please take a few moments to read this very interesting and informative discussion on White Balance, it will give you a completely new appreciation and understanding of the significance of using the gray card correctly.

Dear Siegfried,

I used gray cards many years ago. I’ll tell you what I remember about them.

I got them in the early 1970’s from Kodak. They were very sturdy cardboard, about one eighth of an inch thick. The size was 8x10 inches. One side was white, and the other side was 18% gray. The laws of physics say that all colors come to gray. That is, if you stack the same densities of all three filters (either primary or subtractive colors) you will see gray. The gray side was ideal for getting incident readings from a hand held light meters. It gave accurate exposures given any ambient lighting condition. However, they were most valuable for color balance.

There is no white balance on film cameras. You bought film balanced for the color temperature of the light you were using. For example, daylight film is balanced for 5000 to 7000o Kelvin, which is the average color temperature of the sun without thick clouds. Indoors you bought tungsten film balanced for 3200o k which is the color temperature of the filament in a household light bulb. (or 3400K film for use with #2 photo floods).

Of course you could buy color compensating filters that fine tuned, or corrected for using the wrong film. I think they were Kodak’s 80 series filters. Fluorescent lighting was always problematic because it had a green spike in its color spectrum. Electronic flash was a blessing because its color temp was around 5200K and you could use faster daylight films on indoor flash pictures.

Photographers had to know all about color and filtration because of wet darkrooms. The latent image on the negative had to be reasonably well exposed and somewhat color corrected before processing. Note: It’s not economical to process film; and it’s too tedious to make color prints by hand in a wet darkroom if your volume is high. Most of us used color labs. There was everything from storefront mom and pop labs, up to the big commercial labs that demanded guarantees of so much money per year.

You’ll better understand what the gray card was designed for if we eliminate some of the variables in the lab. Let’s assume the temperatures of all the chemicals in all the labs were exactly right, and nowhere near exhausted. The main variable then is the operator who determines what values of cyan, magenta and yellow to dial in the enlarger. Mom and pop might do it by eye and come up with what he thinks is a nice print. The problem with that was the color balance print-to-print was often different. The big labs would use a color probe. If it was not be properly calibrated, the whole roll was off color.

The solution to consistent accuracy from the lab was the gray card. You had to carry it with you. When you put in a fresh roll of film, make sure the first picture was the gray card itself in the light you were shooting. Completely fill the frame with gray. It does not have to be in focus.

Now the operator can compare that first frame with the gray card in the lab and dial in corrections until they look the same. The rest of the roll would be perfectly balanced to that lighting. If you had a good rapport with the lab, you could change lighting mid roll. Say you went from the studio to the out of doors with the same roll. Simply shoot the gray card again and he would readjust the next set of exposures accordingly.

Slide films were different. They had to be exposed within a half stop, and developed in stable chemistry. If the first developer was too hot or cold, or somewhat exhausted, the slide didn’t match your meter reading, in spite of the gray card. That’s when bracketing was invented.

The physics of the human eye and color spectrum are exactly the same in the electronic medium. Printers are good examples. Combinations of the three subtractive colors yield any and all of those beautiful colors our eyes can interpret. Why then do manufacturers insert extra ink cartridges with subtle hues in between? Perhaps they want to sell more ink. Another reason could be to compensate for mechanical inefficiencies; similar to using a gray card to compensate for the lab’s chemical inefficiencies.

I have experience with available light in the extreme. I took many photographs by candle light, including my share of fireplace shots on medium format film. I think what you are after is to duplicate (in the electronic medium) the ambiance created by daylight film when it’s used on low color temperature light sources such as light bulbs. The warm glow can be stunning as long as the contrast ratio isn’t too high.

Forgive me for saying that you should consider yourself lucky to have an electronic darkroom. Combined with the superb white balance in your camera diminishes the need for gray cards considerably.

My film shots were out of gamut, but that’s what gave them that warm glow. Your white balance guarantees all the colors are in range from any light source. Thus, the electronic darkroom has the full spectrum to explore and replicate that warm glow. The entire process only takes minutes verses hours in a wet darkroom, or waiting days for the lab. The mix of chemicals, film, and enlarging papers were much more costly too.

I have an opinion on comparable quality, but I think that’s too argumentative right now. I don’t know. Anyhow, I hope my experiences were useful.

It’s always a pleasure to hear from you. Please feel free to write.

Best regards and good health.

Sincerely,

Geoff Klimas, Sr.