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04/17/2003 12:25:27 PM · #1 |
I've seen stuff about white balance in the forums a little today, and I must admit I'm not very familiar with this function. My camera has all the settings (cloudy, sunny, twilight, whatever) for whitebalance and it has a manual whitebalance set function, as well. I've never touched any of them--I have no idea what they do. Please share your knowledge with us newbies about whitebalance. What is it? How/when should it be adjusted? What affects can you achieve by customizing it?
Thanks in advance. |
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04/17/2003 12:31:55 PM · #2 |
Light can come in different colors: sunlight, flourescent light, incandescent light, etc. These different colors will, by definition, impact the way color is reflected off of your subject.
White balance settings attempt to correct for these variations by actually shifting the colors in the captured photo. For instance, a photo taken with a WB setting of "incandescent" would, I'd imagine, turn down the yellow a bit, to make up for the yellow/orange tint from a light bulb.
Another way to do all this is to worry about white balance while "developing". The pros will use grey cards to note the light color at the beginning of every shoot. The will examine this grey card photo, and derive some parameters that need to be applied to return this grey card to it's correct, known RGB values. These same parameters can then be applied to all photos from a shoot.
A layman's way of doing this is to look for something in your photo that is a known white (best case), or a known grey. Then set your white point (or grey point, depending) to that location in the photo. You can do this in the "curves" dialogue box in photoshop. |
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04/17/2003 12:39:51 PM · #3 |
Here goes ...
'White Light' does not really exist - it's always toned between blue and orange to a greater or lesser extent. The light of a bright sunny day is in fact quite blue (due to the amount of sky visible). The light of a normal household light-bulb is quite orange. The measurement of this quality is in degrees K (for Kelvin) - high numbers (upto 8000 deg K) are blue, low numbers (usually down to around 1200 deg K) are orange.
Likewise, the 'colour temperature', as this phenomenon is referred to, is different on a cloudy day (bluer still), and under flourescent lighting, halogen lighting, in fact any kind of lighting at all. Your eyes, however, adjust to this difference quite comfortably, so you don't see it. The 'white balance' settings on your camera are factory presets to match the colour of ambient light to that percieved by your eye. This is why if you shoot on a cloudy day with your camera set to sunlight mode all the shots look very blue - your camera isn't doing enough to counter-act the ambient light. Most newer cameras can be set to automatically work out the correct 'WB' - though certain situations can fool them.
The manual setting will give you a scale of K - probably not the full range - so you can select what point on the blue/orange scale you want the camera to think is out there. Many cameras have programmable WB settings too - focus on a piece of grey card and you'll get an accurate reading: this is often overlooked when taking portraits, and can be essential to getting skin tones right, which are highly sensitive to the colour temperature of light.
Did that make any sense?
Ed
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04/17/2003 12:41:00 PM · #4 |
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04/17/2003 12:41:54 PM · #5 |
Another way to look at it is that light comes in different temperatures (Kelvin). Sunny days are 5500D Kelvin. If your camera is set to shoot on a cloudy day (around 4800K I think) the images will come out blue shifted because you shot a 5500D day at 4800. The problem is that the standard settings on a camera (sunny, cloudy etc...) are broad strokes. There is 500D +/- between each setting. A white card or grey card allow you to dial in the actual temperature (ex. 4875D) and have true color rep.
Like Welcher I shoot with a 10D. I shoot mostly RAW. That gives me the ability to change my white balance after I have shot. Capture one just released software that has a kelvin slider so that you can adjust the temp from 2500 up to 10,000 in 1 unit increments I believe. That way I can make the color absolutely accurate to what I remember.
White balance is (IMO) the single most important thing in capturing images technically next to comp and focus.
Dave
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04/17/2003 12:46:20 PM · #6 |
Hey Ed, aren't lower numbers cooler (blue) and the higher ones warmer (red)?
Dave
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04/17/2003 12:48:50 PM · #7 |
You've got me wondering now - I've thought for years it was the other way round ...
E
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04/17/2003 12:55:19 PM · #8 |
Nikon Bloke's article
Phew - I'm right. Higher=bluer.
That's a really good article though - never knew what the standard was!
Ed
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04/17/2003 02:32:17 PM · #9 |
| That is a good article. All of this is also why you find special lights in print shops set to 5000-5500K for viewing proofs and printed sheets. |
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04/17/2003 04:31:33 PM · #10 |
Originally posted by GeneralE:
That is a good article. All of this is also why you find special lights in print shops set to 5000-5500K for viewing proofs and printed sheets. |
Also makes me wonder if digital makes a lot of the high end, expensive lighting equipment obsolete - or at least makes the argument that they are so expensive because the colour temp needs to be carefully regulated no longer true. Cheaper lights that can be corrected for in camera seem to be made possible by the variable temp white balance in digital cameras - although I guess that's only true if the lights are all the same temp. |
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