In Reply to Chris about White Balance
Hi Chris,
White balance is a pretty technical subject. Let’s go simple first then a more detailed explanation follows below that.
White balance is a misnomer but is universally used. Correct white balance is really important for food because the color of food gives us a lot of visual information. It’s not just about a white plate
. Look at my example above with the plated chicken. It’s not the white plate, although it has been corrected. It’s about the green beans! In the bad shot the beans look golden and not very appetizing. In the corrected shot they look perfectly “beans” green and delicious.
SIMPLE ANSWER
Chris, the simple answer is to try to get the light right before you shoot. JPEGs used by most people are like film. The only adjustment is to use color correction filters in front of the lens or in post. This is not as easy with digital as with film because film is a known quantity (always perfect daylight white balance) while digital cameras are mostly set to “auto” white balance, phones have no other setup. What this means is that the white balance is computed automatically for every shot. This is potentially disastrous because it means that every single shot can have a different white balance!
So, the simple answer is to use a “daylight” bulb for all the food shots. The bulb mimics daylight and cameras and food love that. This is very easy to do. But, if you are going to use a light fixture that you have to handhold then you are back to using a tripod
.
Look for clamp on reflectors at Amazon and also look for “daylight” (5500K) fluorescent bulbs that have 85 watts of output. Very inexpensive and easy to use both indoors and out by the grill at night. You can even put a white cloth in front of the reflector and presto, homemade diffuser. And, it gets better. The light output is highly adjustable. Light works with the square of the distance so by cutting the distance from the bulb to the food in half you increase the amount of light by four times
.
Here they are at Amazon:
http://www.amazon.com/s/?_encoding=...alias=aps&linkId=7YNOYABUMR63EFCW?tag=TVWB-20
and:
http://www.amazon.com/s/?_encoding=...alias=aps&linkId=J3EZQSVJZEM2QONL?tag=TVWB-20
MORE DETAILED EXPLANATION
One of the qualities of visual light is its perceived color temperature, usually expressed in Kelvin (K) degrees. We all know that the light we perceive just before sunset seems a lot warmer than that of the midday Sun. That’s color temperature.
The analog (base measurement) of color temperature is that of the midday Sun. In midday Sun we see pure white as pure white. Close to sunset we will see the same white as a warmer gold color (yellow and red mixed in). This analog is why if you look at a box of film it will say “daylight” somewhere on it. Most film is white balanced for daylight, and that is all you get. It can’t be changed. Some are labeled as “Tungsten” and those are rare these days. They are used for shooting indoors. Indoor lights have different colors too. The incandescent light bulb is even warmer than sunset light. That’s why a white plate will look yellow indoors when shot with “daylight” white balance.
OK, so what about the cameras?
As far as I know phone cameras have no white balance adjustments. Most P&S cameras do. More sophisticated DSLR cameras have complete control of white balance.
Most cameras produce a JPEG image, some more sophisticated ones give you access to the RAW image from the sensor. RAW images allow you to use the same white balance controls built into the camera, like taking the shot as often as you like in the computer afterwards while adjusting it to your liking.
Then again, film has no possible adjustments and has been used forever with good color reproduction. How is this possible? Well, film is a known quantity. It is very carefully balanced to daylight white balance. Photographers know how to correct the temperature of film by adding specific color correction filters. It has been done forever.
JPEGs are like film, the image is done the minute it’s shot. From there only filters can correct white balance. And there’s a further problem. Unlike film, most cameras, especially phones, are set to compute the white balance automatically in “auto” mode. Every shot then can end up with a different white balance. There is no known quantity like with film. So, every image has to be adjusted independently.
Phones, P&S cameras and DSLRs all have an “auto” white balance setting. Phones have just auto and nothing else. And herein lays the problem. If the scene being photographed does not have a
“neutral” white tone somewhere, the camera
WILL be fooled. Some “auto” algorithms are very sophisticated and can come real close, but it is usually not enough in a demanding situation.
It would have been great if phone manufacturers, who give you no white balance adjustments, would have set their cameras like film, for daylight white balance. It would then be a very simple thing to apply the correct filter manually in the camera after the shot was taken.
OK then, so white Balance is the term used, strictly in still photography, to communicate the light temperature adjustments (or lack thereof) that are present in an image.
In simple terms, it is the difference in intensities of Red, Green and Blue (RGB) colors that are present in any one part of the image that has a
neutral “white” color. Remember this last sentence, it is the key. When we see a white object what we are seeing is light being reflected by it in “equal” intensities of RGB.
RGB intensities in the digital world are usually measured in an 8-bit scale because that equates to JPEG images, JPEGs are stored in 8 bit space. The range is 0-255, for 256 colors per each RGB channel. So, pure white (no detail) is RGB 255,255,255. Pure black (again no detail) is RGB 0,0,0. But, those values are never used for white balance calculations because the differences in tone for the other parts of the image can’t be measured. Depending on who you ask
Neutral “white” color used in white balance measurements is somewhere around RGB 128,128,128 and that is not white, it’s grey
. This is why photographers have used specially manufactured “Grey Cards” forever. Confused enough? It gets easier now.
Neutral white, or middle grey, is the ideal color to compute white balance. But, how often do you have that in an image? The answer is pretty much never. So, how do we get good white balance?
1) We can shoot in auto and hope for the best – not very accurate and can be frustrating.
2) We can shot in one of the other white balance modes built into the camera (not phones) and again hope to get close – still not quite accurate but better that #1.
3) We can adjust in post processing – easier said than done without sophisticated software for JPEGs.
4) We can shoot in RAW and adjust in post processing – easier and pretty accurate but still time consuming.
5) We can get the light just right before we shoot – THE BEST!
Professionals use #5 ALL the time. It is so much easier. So, shoot by a window, use foam board reflectors. Or, use a clamp on reflector with a daylight (5500K) fluorescent bulb. This is the best method and they are cheap. Make sure they put out plenty of light though (see Sin #2 in the post above).
The light and reflector solve not only the white balance problem but with enough light you can avoid most all of the Sins mentioned above as well.
Hope this helps!
All the best,
Jose
