White Balance (1) Intro

[RichardTaylor]

White Balance (1) - Introduction

This is the result of a request

One of the characteristics of light is it's colour "temperature". Think of a warm sunset or cool winters evening.
The unit of colour temperature is the Kelvin low numbers are warm colours like yellow - reds, high numbers are "cool" colours like blues.

For more info on the Kelvin range see this DPS tute.
Creating Moods with the Kelvin Scale

One of the problems when shooting is that the colour of light may be continually changing. A cloud may pass in front of the sun or changes during and after a sunset or you use a flash or you shoot indoors without a flash.

(1) Sometimes you may even have different light sources in one scene.
Here we have both direct late afternoon sunlight on the car & dust and just skylight lighting up the rest of the scene.


Camera Canon EOS 40D
Exposure 0.003 sec (1/400)
Aperture f/6.3
Focal Length 400 mm
ISO Speed 500
Exposure Bias -2/3 EV
Date and Time (Original) 2010:05:02 17:51:36.05+10:00

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The look of the final photograph may be an artistic decision.
Other times it is not, like a brides dress, or product, or even a flower.

How do we control the appearance of colour in the end photograph?
We can control it when shooting by adjusting the "white balance" so that the image is captured correctly or we can adjust it later when post processing (PPing).

A Canon G11 was used for the examples below.

(1) We can let the camera decide by choosing "Auto" white balance.
This may be fine for a lot of scenes and lighting.

(1A) JPG image shot in bright sunny, midday sunshine, using auto white balance
(the exposure has been increase by one stop when PPing).



(1B) JPG shot under the shade of a tree. Most of the light was just blue skylight.
Auto white balance (I feel it hasn't done a real good job)



(2) We can select a white balance setting from a camera menu.
Depending on your camera and how you are using it you may see the image change on the LCD dsplay as you are making your selection..
Here is an example shot the same time using the "cloudy" setting. The G11 doesn't have a shade setting. While it is slightly better than the image above it is still not real good.

I

(3) We can create a custom white balance to be used as a reference
More to come on this.

(4) We can change the white balance when post processing.
More to come on this.

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Thanks for looking and feel free to comment or ask questions.
Richard
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Reference for further info - on the DPS site:
Introduction to White Balance

[bdbolin]

Great post! Thanks!

[FlyingKiwiGirl]

Originally Posted by RichardTaylor

(3) We can create a custom white balance to be used as a reference
More to come on this.

Thanks Richard! This is the one I'll be waiting on.

[RichardTaylor]

Custom White balance (1)

This series was shot with a Canon G11 under a domestic florescent light.
The only PPing was cropping and a small levels adjustment on the original jog files.
Same subject as above.

(5) Using Auto white balance setting.
The variation between the red, green, blue channel was <1 (basically it was very good)
With just a couple of outdoor test shot on a cloudy day showed similar results for both the cloudy and auto settings..



(6) Daylight florescent setting (I didn't know what sort light we had)
The variation between the red, green to blue channels was 12 to 20 (no good)



(7) Warm-white florescent setting.
Almost identical results to the Auto setting (very good).
Image is not real sharp as I have trouble hand holding at 1/13 second.


(8) Custom white balance.
On a G11 this is done by filling the display, with the exposure setting correct, with a white subject under the light you will be using and pressing a couple of buttons. The results are visible immediately.
On some Canon DSLRS it is done by taking a picture of a white subject that fills the screen and using this as a reference (you make some menu choices).
Check your camera manual to see how to do it.

The results were almost identical to Auto white balance and the Warm-white florescent setting.


I tried a custom with balance outside under an overcast sky.
The results were slightly warmer than what I expected (a problem with my technique?). The Auto and cloudy white balance worked better

It seems to me that you use a pre-set (except Auto) white balance you do need to know your light source and also keep track of any changes .

If using a custom white balance then the reference subject needs to be correctly lit when recording it. If there are any changes to the light the custom white balance will need to be changed.

From a personal point of view shooting RAW appears to be the way to go especially in changing light.

More to come..

[RichardTaylor]

More on custom white balance.

A section of urban parkland. Lighting was street lights + a bit from passing cars, during the 15 second exposures, and a nearby shopping centre.

(9)
This is what Auto white balance returned (the pre-sets were not any better) and all looked awful on the camera LCD.


(10)
This is with a custom white balance with a makeshift "grey/white" card (the back of an old receipt I had in my wallet. This didn't look to far removed from the actual scene and would look even better darkened (it didn't look that bright) .



White balance bracketing

Some cameras may have white balance bracketing.
This was from a Canon 40D with maximum red/blue bracketing turned on.
Just shooting one exposure will take an Auto white balance pic and create another two images at both limits of the bracketing. The results, at least on the 40D, are subtle.
Check your camera's user guide for more info.

(11)
This is the "standard" AWB shot.


(12)
This is a composite of both red/blue limits on the above pic.


More to come .

[RichardTaylor]

Custom white balance (3)

Sometimes even custom white balance won't get it tight.
All pics taken with a Canon G11 point & shoot camera, in shade on a bright sunny day.

(13) Auto white balance returned this.
Notice how the white panel, on the top left, isn't really white.

.

(14) A custom white balance (using the white panel) as a reference returned this.
A little better.


(15)
Here the white balance was adjusted from the RAW file, when post processing, taken at the same time as pic #13. I was shooting RAW + jpg.



The card looks just like this. The white is white.

More to come -

[RichardTaylor]

White Balance - RAW

Sometimes auto white balance, custom white balance, or a pre-set will not give you the results you want.
Sometimes you will not be in a postion to create a custom white balance when shooting or a particular scene will have more than one correct white balance.

This is one reason I shoot RAW and adjust the white balance, if needed, when post processing. Depending on the software you are using you may have a lot of options.

Larger pics are on my flickr stream.

(16) Here is an example of where just one white balance setting will not do the trick. The end picture is a composite of two files created from a single RAW file.
The brickwork and roof on the left has had the exposure and white balance adjusted to allow for the shade.



(17a) In this example I can't place my self at subject location to do a custom white balance, or take remove my eye from the viewfinder to adjust the white balance.
I was shooting RAW. Lighting conditions were late morning (10:29am) clear sunny day with the sun mostly off to mostly off to my left, note the shadow.

This was how the camera interpreted (as shot) the scene. The white has a bit of a blue tinge through it and the dark green car is slightly blue.


(17b) After white balance adjustment when PPing.

.

(18) White balance can be used as a creative tool. This winter sunset, which looked rather cool, has been warmed up by an "incorrect" white balance adjustment when PPing the original RAW file.



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To summarise.

(1) Know your camera (take test shots etc).
Understand how Auto white balance works, or doesn't work, in different lighting.
Know how to use pre-sets and this will also mean knowing what type of light you are shoooting in.
Know how to set a custom white balance.

(2) When shooting be aware of lighting changes that may affect white balance, and that may just mean a cloud in front of the sun.

(3) Take some test shots and see how they look. For some camera's you may be able to see the results of white balance settings without even taking a photograph.

(4) For maximum control over the final image (and sometimes the only alternative) is to learn to shoot RAW, and there are some downsides tro shooting RAW, and learn how to post process the files. (I almost always shoot RAW).

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Some references

(1) A general discussion on white balance,. including some additional tools.
CameraHobby - White Balance Tools

(2) Using white balance as creative tool (on this site)
Using White Balance as a Creative Tool

(2) Also on this site: Using a grey card.
Get your White Balance Right in Seconds Using Grey Card

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Thanks for looking and feel free to comment and ask questions.

Richard

[FlyingKiwiGirl]

Wow Richard, that last shot is really fantastic, love it!

Now I have just got to read all the above again and get most of it to stick. I really do get the gist of WB, it's just some situations and the corrections for those that stump me. Sometimes I feel I'm going around in circles. I'm going to have a think and see if I can post an example and get your comments.

Thanks very much for doing these tutorials, they are worth their weight in gold to relatively newbies to dSLRs. Much appreciated.

[Gordy UK]

Now i think i got some of that....but as Flying Kiwi Girl stated....will have to go back and see if some of it will stick.

Excellent tute though Richard and I also think that last photo is fantastic. I'm off to Canada next year and that sort of photograph pre or PPing would be great to acheive.

Thanks again

[RichardTaylor]

Thanks very much guys. I learnt a few things also..

Gordy
We were lucky enough to have two weeks in Canada (basically the Rockies & Quebec) as part of our 2008 vacation. It a great place if you are into landscapes the Rockies are like heaven.