This may be either a silly question or one that is too complicated. If I set white balance to a particular temperature, what is it actually doing? Does it take the light the sensor receives at that temperature and adjust it to white?
It takes the exposure and "corrects" it to match the kind of light you set it for to end up with the right colors.
It is all about the color of the final image.
If you take a shot inside under house lighting, it would normally be on the red side,so you set the camera to "indoors" and it corrects the image as if you took it with film and had the right filter on the lens. The filter would correct the exposure for the red lighting.
All the white balance does is act like a filter to correct the color balance.
Actually it doesn't act exactly like a filter in the sense that a filter will change the recorded data (on film or a digital sensor if using JPG mode). When using RAW mode the image data saved to the card is always the same, and the white balance setting is saved merely as an indication to the converter and can be changed after the fact with no loss of data.
What the white balance setting actually does is as you describe - it tells the camera (or raw converter) where the white point is, based on a given color temperature, which in turn uses that setting as a reference point to map/compensate all other colors accordingly.
The more interesting funciotn here is when you set the camera to auto white balance, in which case it needs to make an educated guess on what the ambient color temperature is by acting as a colorimeter.
Guy
Posted by Jack Graham on March 18, 2006 at 11:22 PM
Folks,
After having my new NIKON D200 for a week, I never realized on how the white balance settings can make such a big difference .All your help & input has really helped this "old film guy" to understand white balance.
Thanks
Jack
Posted by Randy Beacham on March 19, 2006 at 11:34 PM
I just bought my first digital camera and was thinking of posting a question concerning white balance just as you did so the answers are interesting.
So here's my question--or maybe I should post as a seperate topic. If I have white balance on auto like I'm doing right now, can the balance be thrown off by real light or dark subjects as happens with exposure meters? The reason I ask is that some of my snow scenes seem to be very flat and also too gray--even if the exposure is close to being overexposed. I guess it's time to pull out my old photography magazines and go back over digital articles now that I have a digital camera. Randy
Yes, auto white balance can be thrown off if the scene has an inherent/consistent color scheme that makes the camera think is related to color temperature rather than the subject itself.
If your snow comes out neutral gray then there's nothing wring - the white balance did its job. Cameras intentionally capture low-contrast to avoid clipping. A quick levels or curves adjustment will snap the whites back to where you want them.
Guy
Posted by Randy Beacham on March 20, 2006 at 12:51 PM
Hi Guy,
So what you're saying is you think it's better to run white balance on auto and then adjust using curves and levels rather than custom set the balance if you're photographing a scene like white snow? I'm having a problem running curves and levels and getting the gray out without blowing the whites out.
The cool thing I'm finding out about digital is I can go out today and experiment with settings like white balance and be evaluating the results this evening! And all without spending $15 for every 36 exposures to experiment--I like that! Randy
If you're processing raw file (which I guess will not be until you get a new computer), then the white balance setting simply gets recorded as an attachment to the file and can easily be changed after the fact when you're seeing the image on a large calibrated monitor - this is definitely the most effective way to get accurate results.
With JPGs it gets more tricky since the white balance setting actually affects the way pixels are recorded in the file and correcting after the fact may be more challenging.
Either way, the role of white balance is to establish color neutrality, or eliminate color casts, not to produce bright whites.
Assuming the white areas in your image appear gray then white balance did its job. You should only need to set the white point to make the whites brighter.
Guy
Posted by Randy Beacham on March 20, 2006 at 3:07 PM
Okay, thanks. I'll see how things work when I go to process the raw files. Randy
Thanks for the information. The give and take on the topic has been helpful. One of my issues is that I pick up a green cast in some of my photos that I think is related to white balance. What I do is make sure that I shoot in RAW if I'm not confident that I won't get the color cast.
For those shooting in JPEG it is best to experiment with white balance settings for situations where you don't want to eliminate the color cast - for example I hear that many people have success shooting sunsets with the white balance set to cloudy.
Discussion
9 repliesJim
It is all about the color of the final image.
If you take a shot inside under house lighting, it would normally be on the red side,so you set the camera to "indoors" and it corrects the image as if you took it with film and had the right filter on the lens. The filter would correct the exposure for the red lighting.
All the white balance does is act like a filter to correct the color balance.
What the white balance setting actually does is as you describe - it tells the camera (or raw converter) where the white point is, based on a given color temperature, which in turn uses that setting as a reference point to map/compensate all other colors accordingly.
The more interesting funciotn here is when you set the camera to auto white balance, in which case it needs to make an educated guess on what the ambient color temperature is by acting as a colorimeter.
Guy
After having my new NIKON D200 for a week, I never realized on how the white balance settings can make such a big difference .All your help & input has really helped this "old film guy" to understand white balance.
Thanks
Jack
So here's my question--or maybe I should post as a seperate topic. If I have white balance on auto like I'm doing right now, can the balance be thrown off by real light or dark subjects as happens with exposure meters? The reason I ask is that some of my snow scenes seem to be very flat and also too gray--even if the exposure is close to being overexposed. I guess it's time to pull out my old photography magazines and go back over digital articles now that I have a digital camera. Randy
Yes, auto white balance can be thrown off if the scene has an inherent/consistent color scheme that makes the camera think is related to color temperature rather than the subject itself.
If your snow comes out neutral gray then there's nothing wring - the white balance did its job. Cameras intentionally capture low-contrast to avoid clipping. A quick levels or curves adjustment will snap the whites back to where you want them.
Guy
So what you're saying is you think it's better to run white balance on auto and then adjust using curves and levels rather than custom set the balance if you're photographing a scene like white snow? I'm having a problem running curves and levels and getting the gray out without blowing the whites out.
The cool thing I'm finding out about digital is I can go out today and experiment with settings like white balance and be evaluating the results this evening! And all without spending $15 for every 36 exposures to experiment--I like that! Randy
If you're processing raw file (which I guess will not be until you get a new computer), then the white balance setting simply gets recorded as an attachment to the file and can easily be changed after the fact when you're seeing the image on a large calibrated monitor - this is definitely the most effective way to get accurate results.
With JPGs it gets more tricky since the white balance setting actually affects the way pixels are recorded in the file and correcting after the fact may be more challenging.
Either way, the role of white balance is to establish color neutrality, or eliminate color casts, not to produce bright whites.
Assuming the white areas in your image appear gray then white balance did its job. You should only need to set the white point to make the whites brighter.
Guy
For those shooting in JPEG it is best to experiment with white balance settings for situations where you don't want to eliminate the color cast - for example I hear that many people have success shooting sunsets with the white balance set to cloudy.