2011-11-24

Using an 18% Grey Card

How to article: Using an 18 percent Grey Card.  This article discusses using in-camera reflectance metering with an 18% grey card.  This article applies to both film and digital cameras.

An 18% grey card allows you to set the camera's exposure using a known reference and the card will give the 'correct' exposure for any scene, regardless of the subject.  I use this method frequently.

Grey cards are literally a grey rectangle made of cardboard, plastic or cloth, and can be purchased from any camera store for about $15 to $30.  What they all have in common is they are made of a photographic neutral shade, averaging 18% grey.  Ideally, you want one that can be folded or cut so it fits in your camera bag.    

Contents:
  • Using a Grey Card
  • Why use a grey card (the proof)
  • Interpreting the results
  • Grey Card reading + 0.5 stops
  • Dark Subjects, night scenes overexposed
  • Light and backlit subjects
  • Controversy and exceptions

Why a Grey Card?

With your camera, do this 1-minute experiment to prove why you need a grey-card:

1.  Place a dark sheet of paper or a dark magazine on the table-top, then cover it with a white sheet of paper.

2.  Using the camera, focus on the white paper so it occupies most of the frame.

3.  Meter the scene, noting the camera's recommended shutter speed and aperture.

4.  Remove the sheet of paper and meter the darker scene.  Note the different exposure.

Questions:  
  • ? Knowing both subjects were in the same lighting, why does the meter reading change when  the subject's color is different?  Isn't the subject in the same quality and quantity of light?
     
  • ? Which meter reading should you use if both the dark and white subject are in the same scene?  

The Answer:  Neither the white or black-paper reading is correct. If you were to actually take the photographs, you would see the white paper looks grey, not white, and the dark paper will look grey, not black.  The issue is this: The camera meter is fooled by the color of the scene and will not set the exposure correctly.


The Camera Meter is Usually Wrong

When a majority of a scene is "whiter than normal" (snow, concrete, light colored walls, backlighted) or "darker than normal" (black subjects, theater stages with dark curtains, night shots), all cameras meter incorrectly.

But here is the surprise: It turns out with almost any scene, any subject, under any lighting condition, the camera's meter reading is wrong to some degree.  This is true with landscapes, portraits and still lifes.  Granted, on an average scene, the meter is close and you will get an acceptable picture, but almost always, a more accurate value can be set with an inexpensive grey card.  

To explain this another way, the camera meter expects a scene to have an average number of rocks, trees, sky, people and things; this is how it is calibrated.  According to Kodak, if you took all these items and spun them in a black-and-white blender, you would get something along the lines of an 18% grey.  Since the camera cannot tell what the subject matter is, it assumes grey and sets the exposure with this in mind.  Examples of missed exposures are shown below.

Better exposure means less post-processing.  Better exposures give better colors, with better shadow details and this is true with film, digital and digital RAW.  


(For reasons that are too complicated to explain here, all cameras, film and digital sensors are calibrated for 12 to 14% grey, depending on the manufacturer.  Grey Cards are calibrated at 18%, for black-and-white printing -- meaning the grey card is not quite right.  This article explains how to work around this.  The world really needs a 13% grey card.)


Buying a Card:


Grey cards can be made of cardboard, plastic or cloth and ideally should be waterproof -- but I have found some plastic cards too glossy.  My card is the cardboard variety and because it is not waterproof, I have to replace it every few years.  But being cardboard, I can cut it to any size; mine is about 6x8".  For in-camera metering, it should be at least 5x7" or larger.  The back of the card should be white, which I use for White Balancing.

You will see some credit-card-sized cards.  These are meant for post-processing and are too small to help with in-camera metering.

I do not have any brands to recommend, but here is an Amazon link to get you started:



Using the Card

For in-camera metering, follow these steps
  • For simplicity, set the camera to Av mode (aperture preferred) or Tv (shutter preferred)
  • Hold the grey card in the image area
  • It does not need to be accurately focused but it must be in the same quality of light as the subject.
  • In the view finder, it should occupy most of the image area.  Zoom if needed.

  • Angle the card between the lens and the main light source so it does not glare
  • Do not cast your own shadow on the card
  • Note the exposure (Shutter speed and aperture).  This is the exposure that should be used, plus 1/3 to 1/2 stop, as explained below.
Although the grey card does not need to be in focus while metering, some cameras, such as my Nikon D5100, struggle with auto-focus on a featureless grey card, especially in dim light. You won't be able to use a focus-lock on the edge, because that will also probably lock the exposure.  You may need to temporarily set the lens to manual focus.

Interpreting the Grey Card:

1.  While metering the card, note the exposure.
2.  Then remove the card and re-meter the actual scene.

3.  *If* the exposure changes (either the shutter speed or aperture changes), then exposure compensation is needed.  Use the grey-card's reading for your final exposure, plus a third to half-stop, as explained below.


I find it easiest to set the camera in either Aperture Preferred (Av) or Shutter Preferred (Tv) mode.  This way, only one meter value changes as the card is removed.  For example, if in Av mode, the aperture stays fixed and only the shutter changes.

In the viewfinder illustration above, the grey card metered at
125 @ f5.3 (this is the grey card's recommended exposure).
Without the card,
250 @ f5.3,

indicating a +1 stop (+1.0EV) over exposure is required.

Because the grey card is 18% grey, but the camera is calibrated to approximately 13%, add an additional 1/3 to 1/2 stop to the grey-card reading.  The variation of a 1/3 to 1/2 depends on your camera.  Some cameras jump in third-stop increments and others, especially older cameras, use half-stop increments.  The difference is immaterial.

The final adjustment can be seen on a graph:


Setting the Compensation:

There is no need to count or calculate the number of stops. 

Start with the camera's recommended meter reading.  Then, using your camera's Exposure Compensation controls ("+/-"), spin the dial until it reaches the grey-card's recommended setting, plus one click for the +1/3 (or +1/2) additional. 

Cameras vary in how this is done, but most work similarly.  Illustrated below, is the Nikon D5100's compensation controls.


When adding that last +1/3 to +1/2 stop, use 'one more click of the spin-dial' from the grey-card setting.  If under-exposing, spin the wheel the opposite direction (remember, you are always 'adding' the last-click - even if under-exposing); see the 'dark subject' example, below.  As a reminder, under-exposure means "less light," with shorter shutter speeds or narrower apertures but you still need to add that last 1/3 stop.

See also this handy reference/counting chart: Fractional Shutter Speed and Aperture chart.


Important Note: In order to use 'Exposure Compensation' the camera must be in a non-automatic mode (switch the camera's mode dial off of fully-automatic (the green mode) and place it in either Aperture Preferred (Av), Shutter-Preferred (Tv), Programmed (P).  Most cameras, in the green-squared, fully-automatic mode will not allow exposure changes.

A little history:  For decades, grey cards were simpler to use:  You would use the grey card's reading without any other adjustments.  But with digital cameras, histograms, and a lot of experience, along with the fact that camera makers publicized how their meters were calibrated, photographers came to the realization that additional compensation was needed.  You should now always add 1/3 to 1/2 stop from the grey card's suggestion, regardless if you are over or underexposing.


Re-Metering 

Once the Exposure Compensation has been set for a particular scene or composition, the camera can remain at this setting, even if the light changes.  For example, if a cloud passes overhead, the meter may change but you do not need to reset the compensation because the scene did not change.  Similarly, if you add a polarizing or other filter, you do not need to re-compensate.

However, if you re-compose the picture and point to a new subject,
  • Re-set the compensation to zero
  • Re-calibrate with the grey card. 
It is easy to forget to reset calibration to zero when re-metering the grey card.

Some people like to set their camera to pure-manual and set the exposure compensation that way.  I think this is a mistake and prefer using exposure compensation.  If the quality of light changes, the camera will automatically adjust, but in Manual mode, you would have to re-meter.


Examples: 

Dark Subjects = Under Expose


Camera meters are fooled when a dark or light subject fills most of the frame; especially if you are using a center-weighted metering system.  The subject's color can affect the meter.

You have probably seen metering errors. Here is a great example from Canon Camera's website, showing how a darker than normal subject can fool the camera meter into over-exposing.  Note how the black car is nearly grey.  You would see the same problem taking a night or stage photo where most of the scene is black.  In each case, the camera would overexpose:


To properly render a dark subject, under-expose from the camera's recommended meter reading.

This is counter-intuitive.  Remember, you are compensating for errors made by the camera meter.  To 'preserve the black, under-expose'.  In this case, you could guess at (-1 2/3) stops or use a grey-card to get the exact value.

For example, with a dark subject, the camera might recommend 1/100 @ f8 (over exposing) while the grey card might recommend a 1 and 2/3's stop under exposure.  As before, set the exposure compensation to the grey card's reading -- under exposing to a shorter shutter speed -- then spin the dial the other direction, adding that last +1/3 (or +1/2) stop.  

Adding the (+1/3) stop compensates for the camera's 12-to-13% vs 18%) calibration difference. 

For night landscapes, or dark night-time sky photos, a grey card will not work well.  Set the exposure compensation to -2 stops (2EV under exposure) and let the camera meter normally. 



Light Subjects = Over Expose


With snow scenes, the camera assumes the subject is likely about 14% (18%) grey and it will try like the devil to make it so.  It does this by (accidentally) under-exposing the snow, making it obviously grey.  You correct the faulty meter reading by manually "over-exposing."  This is also counter-intuitive: On a bright snowy day a good rule of thumb is to over-exposure the meter reading by 1 3/4 to 2.0EV stops.  This keeps the snow white.  Naturally, you can meter off a grey card to get the exact value.



Scenes where most of the image is white will demand a +2.0 stop over exposure -- provided the white fills most of the scene.  You will see this with white or light-colored walls, concrete, etc.. If other subjects occupy space in the same frame, you will need less of a value and it is even more important to meter the card.

Of interest, when deciding to compensate (say for snow), it is the color of the subject that determines what you need to do -- not the brightness of the light.  In the middle of the night, the same snow scene needs to be over-exposed the same +2 stops as on a bright or cloudy day.


Backlighting

Backlighting adds some complexity when using a grey card.  In this next example, the sun is in the top-center of the frame, the bright sky, the nearly white aircraft, and the nearly-white concrete runway all occupy most of the frame.  The camera incorrectly metered, under-exposing the scene (note especially the near silhouetted person, who humorously appears to be the real subject).  To compensate, meter with a grey card (or guess at a 1.0 to 1.5 stop over-exposure).

Greycarding in a backlit scene is more complicated.  In this example, hold the grey card, as you were facing the scene.  Literally, place the card right in the scene, as shown above, but you won't be able to angle the card into the sun.  The backlighting will cast the card in its own shadow.  If you were to use that exposure, the highlights in the scene would be blown into near pure white and the shadows would be as-if high noon.  In this instance, I would back-off the exposure 2/3rds of a stop (shorter shutter speeds or narrower apertures), allowing the shadows to remain.

(This photo is a good candidate for an HDR shot, as long as nobody were moving.)  If you were actually taking a picture of the woman in front of the plane, move in closer and take her picture, not the planes.  Then I would meter the grey-card normally.


Grey Cards and Normal Pictures

Even with seemingly normal landscapes and portraits, the meter is likely off.  For example, in a portrait, caucasian skin is easily 1 stop whiter than grey and if a person occupies a significant portion of the viewfinder, this will throw-off the meter.  A grey card will give a better meter reading.

Similarly, landscapes with dark foliage, expansive skies, wheat fields, etc., are all out of the norm and a grey card can help set a more appropriate exposure.  You would be surprised in how often a better meter reading can be found.


White Balancing

Exposure compensation adjusts for metering errors and for artistic reasons.  With digital cameras, there is also a separate problem with "white balancing," also known as color correction.  See this ImageLiner article: White Balancing.

With my photographs, I often do the following:
1.  Set the White Balance
2.  Meter a grey card and compensate as needed


Using a Grey Card in a Post Processing

During a shooting session, where you are taking multiple pictures of your subject, have a model or assistant hold the grey card while you take their photograph in the same quality of light as the subject.  In post processing, use the photo editor's brightness and contrast tools to hand-pick the center grey-scales in the image.  At the same time, most tools will white-balance.  Once set, apply this curve to the remaining photographs from the photo-shoot.



However, setting the grey-scale mid-tone curve in this fashion is an after-the-fact process.  Better results, with the the best quality highlight and shadow details, are found when the exposure is set properly during capture. 

If you use the in-scene grey-card in post-processing, you may loose some of the shadow details, which were never captured because of exposure problems. 

Consider the black car example, above.  No amount of post-processing can salvage the glossy paint reflections captured by the over-exposure -- even with an in-scene curve adjustment. And with the under-exposed example, there are simply no details to recover in the shadowed areas because pixel values were never recorded.  In this example, even after brightening, the subject will be blocky and ill-formed.



Ideally, if you metered with the grey-card and properly white-balanced, you would see no difference in post processing with this technique.


Controversy 

Using an 18% grey card reading for the actual exposure has been the gold-standard for metering and it has become somewhat of a religious issue.  The change in procedure, adding 1/3 to 1/2 stop to the card-reading, is a relatively new idea.  You will find conflicting advise on this topic, with most  referencing out-of-date sources that do not take into account modern cameras and published specifications (references at the end of this article). 

After much studying, and with my own photographs, it seems clear that a grey card was originally designed to solve printing problems - not necessarily to calibrate light meters. But using the card in this fashion is clearly better than allowing the meter to automatically gauge the scene.  By making a minor, last minute adjustment of +1/3 to +1/2 stops (due to camera differences), the grey-card is right on the mark. This is an admitted pain and it would be much simpler if we had 13% grey cards

Before 1980, Kodak recommended an even more nuanced approach:  If a light subject, they recommended a half-stop more light than the grey-card's setting, per the recommendations above.  But if it were a 'dark' subject, Kodak said to under-exposing a half-stop from the grey-card; this is counter to the current recommendations of increasing a half (third) -stop, compensating for the difference between 18 and 13%).  Kodak dropped the idea because it seemed overly complicated but this could accentuate the darker shades.   

Then there is this problem.  In a high-contrast scene, such as a white building in bright sunlight, where there are deep shadows in the doorways and overhangs, and open, lighter shadows on the walls, where should the grey card be placed?   None of the locations give satisfactory results and the contrast may exceed the camera's (film's) ability.  In this case, you have to make an artistic decision: If you meter for the dark shadows (exposing for details in the shadows), the highlights will be lost.  If you meter in the sunlight, the shadows will fall into dark nothingness.  An incident light meter would have the same problems -- where do you place the meter?

Keep in mind, "proper" exposure is not carved in stone, even with a grey card.  There are subjective and artistic points to consider.  In the high-contrast building example, deep black shadows may be exactly what was intended from an artistic point of view.  In this case, meter in the brighter areas.  But if you want both shadow details and usable highlights, you have these choices:  Wait for less contrasty light, such as in the early morning or add fill-lighting to the shadowed areas or use HDR and manipulate the photo in software.



Conclusions

I often use a grey card, especially in landscapes and it provides a solid starting point for the exposure.  Frequently I find the camera's meter is off by 2/3rds of a stop or more and this is easily seen in the final print. By exposing properly, I have less post-processing work on the computer and it is nice to begin with an image or negative that has the best details.

But don't blindly follow the grey card's recommendation.  Artistic license sometimes dictates a change from the "proper" exposure.  There are times when a picture should be under-exposed, deepening shadows, accentuating light sources, etc.  And there are times when a photo might benefit from over-exposures. 

Related articles:
ImageLiner: White Balancing
Reference chart: Fractional Shutter Speeds and Apertures

Discussion thread: 18% grey card vs 12-13%
Wikipedia article on Light Meter Calibration
Reflective Light Meters explained
Histograms and Gamma

Calibration Reference:
Kodak 18% Grey Card: 18%
Canon, Nikon, Sekonic: 12.5%
Pentax, Minolta, Kenko: 14%



Humorous Update 2012.01.03:

For the imageLiner Vanguard Tripod Review, I needed to photograph a white sheet of paper and a coin.  This is literally the photograph taken at the camera's recommended exposure 320 @ f5.6, with no RAW corrections.  Notice how the white paper isn't.  I should have used a grey card and forgot to overexpose 2 stops.  I laughed when I saw the picture. 

Click for larger View; click "X" to return
Keywords:
night scene over exposed overexposed.  night shots overexposed. nightshots grey gray.  exposure compensation, gray card greycard graycard gray-card grey-card.

2011-11-05

Nikon D5100 / D7000 White Balance

The How and Why of setting White Balance with a Nikon D5100 and D7000.  This article deals with a Nikon DSLR camera, but the concepts are useful for all digital cameras.   Edited 2012.12, clarifying various paragraphs.

Photographs take on the color and hue of the light the photo was taken in.  You may have noticed this.  On overcast days, or under dark overhands or foliage, your photos may have a distinct blue tint.  Indoors, photographs may be unnaturally warm (red).  Fluorescents may appear as a variety of unnatural colors.

Your eye (brain) automatically compensates for most of these color shifts but, by default, the camera records the scene as-it-is.  You can use a setting called White Balance to color-correct the scene, setting the colors to "how they are supposed to be."

Digital cameras have an "Auto White Balance" and it can make a guess about the light, but you will get better photographs by balancing the pictures manually.  This article explains how and why to control the white balance.  This is sometimes called Color Correction.

Contents:
  • Examples - White paper under incandescent
  • When to White Balance and when not to
  • Setting White Balance Manually with White Sheet of Paper (recommended)
  • Using Pre-configured White Balance (sunny-day, cloudy-day, etc.)
  • Using Auto White Balance
  • Turning off White Balance
  • "Mood" lighting
  • Histograms

Examples with a White Sheet of Paper

Incandescent lighting (a standard old-fashioned light bulb) has a warm color to it -- verging on yellow or red.  Under normal conditions, people instantly become acclimatized to the light and the brain ignores the color. But from an outdoor (blue-ish) lighting, looking inside of a house, you can see the warmth, which is visible to both you and your camera.

See this article for an example of open-shade color correction:  Still Life with Mussels.

As an experiment, you can test how your camera and its auto-white-balancing behaves by photographing a sheet of white paper. 

With the camera in automatic exposure and auto white-balance, it will likely miss both the color correction and the exposure.  Admittedly, all-white subjects cause other exposure problems, but it is easy to separate the color shifts from metering errors.  In these examples, pay attention to the color.

None of the photographs in this article were manipulated with a photo editor and all were taken under incandescent lighting.




Correct WB and Exposure
Photograph A is how the photo should appear.

A white sheet of paper, a white book, and an apple -- on a light-grey desktop.  The paper is bright white.  With manual "white balancing" and manual exposure compensation, this picture appears as the mind's eye saw it -- even though it was taken under an incandescent light.   

As an aside, the overall whiteness of the scene fools the meter.  Because of this, the picture was over-exposed +2 stops to compensate.  This would be a metering problem regardless of the light, type of camera, film, etc., and is a separate issue, covered in this imageLiner article:  Using an 18% Grey Card.  


Photographs B - Auto White Balance + Manual Exposure Compensation

In this photo, the camera was to over-expose +2 stops, compensating for the white paper, solving the under-exposure problems seen in photos C and D, but the "white balance" was left in "Auto"  (Auto White Balance). 

As you can see, the Auto White-Balance still has a red hue.
Compare this with the all-auto exposure (no white balance, no color correction), illustrate below.  Even with a white balance, the all-"auto" is red (and underexposed):


Photograph D was taken under the worse possible conditions:  The camera was set for a Daylight (not Auto) white balance and there was no exposure compensation to counteract the white-subject's metering error.  The red is overwhelming and even I was surprised at this photo. 



Real-World White Balance

Except for bright, sunny days, almost all photographs can benefit from White Balancing.
This is especially true if artificial lights are used. 

Consider white-balancing in these situations where the color of the light can often look unnatural in the final photograph:
  • Outdoor shots underneath overhangs or shade
  • Cloudy, overcast days
  • Artificial lighting
  • Indoor under a cold, wintery window light
  • Scenes with a brightly-colored backgrounds or colored reflecting surfaces
  • Scenes with a lot of white (snow, concrete, etc.)
  • If you want the objects as their 'true' color

However, for artistic reasons, do not white-balance in these conditions: 
  • Sunrise / Sunsets
  • Candle and firelight
  • Neon and other light sources that are in the photograph
  • "Mood" lighting
For each of these, consider forcing white-balance to 'direct sunlight' (daylight) -- do not allow Auto to adjust.

Use Auto in these conditions:
  • Average day-light (no need to white balance; leave on Auto)
  • If using a Flash when the entire frame is within the flash's range
  • When you are too lazy to do otherwise




Setting White Balance

Follow these steps to set the Nikon D5100's White Balance.  Other cameras have similar steps.

There are three ways to control White Balance:

A. Manual (recommended)
B.  Pre-Sets (choosing a camera's fixed style, such as "cloudy day")
C.  Auto

White Balance can only be set when the camera is in one of these modes:  P,S,A or M.

For reasons only Nikon understands, automatic modes, portrait, landscape, etc,  use Auto White Balance and cannot be manually set.  I suppose this is because these modes were intended to be used by non-technical photographers.

However, if you are reading this article and are concerned about White Balance, you should already be in one of the P,S,A or M modes.




D5100 Manual White Balance with a Sheet of Paper

Method A: Manually Setting White Balance - Recommended Method


In my opinion, the pre-set WB settings (incandescent, shade, etc.) are barely acceptable.  More accurate balances can be set by manually calibrating with a white sheet of paper.  This only takes a minute and the results are always better than the camera's auto white-balance.


You will be taking a calibration photo and this photo will set the correct White Balance for the current lighting conditions.  You will need a sheet of white paper and about 60 seconds of your time.


1.  Confirm the Camera's mode dial is in P,S,A, or M.  You cannot be in Auto-Program, Sports, Portrait, etc.

Have a sheet of white paper handy.

2.  Press "Menu"

In (green) Shooting Menu, select "White Balance". 
Right-arrow to move to the next menu:


Important: You cannot use the "i" menu to manually configure or set the 'Pre' white balance -- even though the "i" menu has a "Pre-set" choice.  "Pre" (as in Pre-set Manual) was an unfortunate name for this choice -- "manual" would have been better.  The name "pre-set" is easily confused with the factory-pre-sets, such as "cloudy-day", "shade", etc. 

3.  In the list, scroll to the last item. 
Select "PRE - Preset Manual"

4.  Press Right-Arrow to select. 

5.  Highlight menu choice "Measure" (OK).  If prompted to overwrite, choose Yes.

6.  In the view-finder, compose on a sheet of White Paper. 
  • The sheet must be in the same quality of light as the subject 
  • For Nikon, the paper must occupy most of the frame
  • Angle the sheet slightly so it partially faces the light source and the camera, with no glare
  • You do not need to be perfectly focused on the paper 
  • Do not cast your shadow on the sheet

7.  Press the shutter to take the calibration photo of the white paper.

Confirmation Prompts:
The video will show "Data Acquired"
The View Finder will show "Gd" (Good).
Note: The calibration photo is not stored on the memory card.

"Pre" (Pre-set manual) white balance is now set.

Photograph your actual scene normally.
Re-calibrate white balance if the nature of the light changes.
You do not need to re-calibrate if the subject or composition changes.


Note: You cannot use the "i" menu to calibrate the PRE White Balance, but you can use the menu to return to the last-recorded calibration. 



D7000 Manual White Balance with a Sheet of Paper

Method A: Manually Setting White Balance - Recommended Method


Calibrating white balance with a white sheet of paper takes a moment and the results are always better than the camera's auto-settings.

You will be taking a calibration photo and this photo will set the correct White Balance for the current lighting conditions.  You will need a sheet of white paper and about 60 seconds of your time.


1.  Confirm the Camera's mode dial is in P,S,A, or M.  You cannot be in Auto-Program, Sports, Portrait, etc.

2. Press and hold the WB button on back panel
    Rotate the control until "PRE" is selected on the top LCD panel
    Release "WB"

 
3.  Return to the camera's normal photo mode by tapping the shutter
4.  While in "Pre", press and hold the WB button again
      LCD Flashes "Pre"; view-finder shows "Pre"

5.  Compose white sheet of paper in the same light and quality as your subject
     Press shutter to take a photo
     Confirm "Good" flashes on LCD
     Tap shutter to return to regular mode

Notes:
* The white balance remains in effect even after power-off
*  Make sure the paper occupies most of the frame
*  You do not have to focus on the paper, but may not be able to release the shutter, depending
    on your settings.  Set lens to Manual focus, if needed
*  The Calibration photo does not actually store a picture.

Be sure to return to Auto when the quality of light changes.


Cautions:

These cautions are true with all white balance settings.
  • White Balance remains in effect until changed. It is easy to forget to un-set.  It can wreak havoc on your remaining photos. 
  • Important: White balance settings even survive turning the camera off.  Remember to return WB to "Auto" when you are done.
     
  • D5100: There are no view finder indicators showing white balance has been set, but you can see the setting on the Video display ("WB").  When Viewing/Previewing a photograph's Information Panel, White Balance is indicated in the Statistics.
     
  • Switching to an Auto-P (Green) (or any of the Scene modes) forces white balance to Auto -- no matter what was previously set.  When the camera returns to PSAM mode, the selected white balance is returned as last-set. 


White Paper vs Grey Cards

A white sheet of paper (or any other uniformly white/grey object) can have some writing or other variations on it, but a clean sheet is best. Some will argue that a white sheet of paper is not precise and is "too white," blowing out the highest registers.  This may be true, but the results I have seen are far better than doing nothing and there is something to be said for inexpensive and handy.  Future articles will attempt to quantify this.


Kodak Grey Cards:  Technically, the paper does not have to be white.  Ideally, it would be a few percentage points less than pure white.  It turns out any uniform, neutral (non-colored) grey would work but finding a "neutral colored" card is hard; I'm still looking.

Standard 18% grey cards can be used, but they are too dark (hard to calibrate in dim light) and most have a slight coloring which can throw off the calibration.  The cards were designed for printing and exposure compensation -- not for white balancing. With all this said, I often use the back-side of my grey-card (a 90% white).


Method B. Using Pre-configured White Balance, e.g. "Cloudy Day":

The camera has a series of pre-configured values, such as "Incandescent", "Cloudy Day", "Shade", etc.  I have never used these values, preferring setting them manually.

1.  Confirm the camera is in P,S,A or M mode.

2.  Press the "MENU" button, open the Shooting Menu (Camera icon), scroll to "White Balance." 

3.  In the White Balance menu, note these options:

Choose from one of the following:










Note: The camera also supports setting the White Balance from a previously-stored photograph.  Ignore this option because the white-paper method is faster and more accurate.
 
Although there is a Fluorescent setting, it probably won't work because of the myriad of different colored lights and some lights give out multiple color spectrums.  Use the manual method, described above, but even that may be hopeless.  Consider using a flash if the subject is close.

Method C:  Auto White Balance:

The Camera's AUTO White Balance attempts to choose the color correction, but as illustrated at the top of this article, it is less-than-perfect.  However, I will use it in bright daylight or when using a flash.  But almost all other times, you should take more control. 

Setting "Auto" White Balance:
1.  Press the "MENU" button,

2. Open the Shooting Menu (Camera icon), scroll to "White Balance."




An alternate path to this same setting is to press the "i" Menu, which opens the Information Display.  Press "i" a second time to place the editing cursor on the adjustable menus.  Scroll to "WB" near the top, right).  Click OK.

3.  In the White Balance menu, choose Auto.


Turning Off White Balance

White Balancing cannot be turned off -- the camera's JPG mode will always attempt some form of white balancing, either in a pre-set or auto-mode.  In any case, when done with any manual setting, return the camera to Auto WB because the setting is so easy to forget.

A.  Using either the MENU or "i" menus, select White Balance (see above)

B.  In the scrollable list, choose AUTO

Confusion Alert:
The D5100 MENU, 'Shooting Menu,' "White Balance," is confusing.  When you return to the WB setting, the menu starts with "PRE - Preset Manual" at the top of the scrollable list.  It is not obvious the up/down arrow keys will take you to AUTO.  (Note: in the "i" menu, it is obvious how the menu should be used.)












"Mood" Lighting

There are times when Auto should not be used. When shooting for "mood" lighting -- where the color of the light is important.  In these conditions, do not allow the camera to use Auto -- and somewhat counter-intuitively -- do not choose Incandescent or any other White Balance setting.

Situations like sunsets, candle-light, street lighting, etc., require a somewhat exaggerated color balance.  In other words, with Auto (or any of the pre-sets), the camera will try to make the scene appear "normal" -- when in fact, you want the color. In these instances, manually force the camera to a pre-set "Daylight," accentuating the color.

In other words, "auto" is not daylight.

A.  Using either the MENU or "i" menus, select White Balance (see above)

B.  In the scrollable list, choose Direct Sunlight (Daylight)



Fine Tuning White Balance:

The built-in pre-configured values (incandescent, flash, cloudy, etc.) can be fine-tuned to a warmer or cooler color than the offered defaults.  You might consider using this when selecting Direct Sunlight (Daylight) and "warming it up" for a portrait. 

This option is only available from the MENU button (not the "i" menu) and is only available for the built-in pre-configured values.  Sadly, these steps will not work with the Manual/White Paper method and this cannot be used when using any of the Scene exposures.

1.  Using "MENU", choose a Pre-Set White Balance, such as "Direct Sunlight"

2.  While highlighting the choice, press the Right arrow.



3.  Use the arrow keys to set a more pronounced color cast.

Note: The center ("0,0") is for the selected pre-configured value.  In other words, Incandescent, cloudy, Daylight, etc., all start at their own (0,0).  When making fine-tuned adjustments, Nikon does not show the selected value numerically.  


This concludes the White Balancing article.
The remaining sections are technical details about the illustrated photographs.



Histogram Details on the Example Photos:

Readers may be interested in the example photograph's histograms.  The on-camera histogram shows Picture D (incandescent light, no White Balance (daylight) and no exposure compensation) like this.

The chart shows the photograph was generally under exposed, with almost all the pixels on the left sides.  The pixels appear by volume and almost all are the "Red" variety.  Picture C (Auto WB, no EC) would show a more centered histogram, but with very few pixels on the right side of the charts due to under-exposure.






Picture A (correctly exposed with manual White Balance, +2 stops EV) as this:

where all colors have approximately the same number of pixels and all the pixels were in approximately the same place -- indicating a mostly-white subject.  Because it was over-exposed two stops, most of the pixels were on the far-right, compensating for the meter's inability to understand the all-white-scene. 




* You cannot blindly accept that you want all of your pixels in the center of the chart.  In this case, knowing the nature of the subject, it is acceptable (required) to have most of the pixels on the far-right of center.  A perfectly-centered histogram does not mean the picture is "perfectly exposed."



What About Color Correction in the Editor:

Can you color correct in your photo editor.  Of course.  But assume you took 100 pictures that day.  You would have to color correct them all.  As long as you are shooting in JPG (not RAW), it may  save you more time if you color-correct when the photo is captured.  (Admittedly, some editors allow you to batch-apply one color setting to all photographs in the session, making this less of an issue.)

With RAW, all bets are off and all corrections are done in the editor.  When White Balancing in the editor, you essentially don't care the color cast when the photo was taken (RAW doesn't even allow you to care), but you must, at least in one of the photos, have a reference shot of a known, fixed color (see Whibal link below, as well as other products).  Unfortunately, this type of card cannot be used for exposure compensation.

The workflow on post color-correcting are different and will be described in a separate article.


Related Links:
imageLiner: Using an 18% Grey Card for exposure Compensation
Reference: Color Temperatures

Article showing color correction in open shade, shadow, blue hue
Still Life with Mussels

There are several commercial products that claim to help with White Balancing.  All of these have my interest, but not yet my dollars.  I'm inclined to purchase WhiBal but in the back of my mind, a white sheet of paper has been doing a fine job.

Commercial link:
WhiBal White Balancing Card ($30 - 50, sized various)
Whibal Purchase (oddly, a different site)
The first link opens to a tutorial.  This product is designed to White-balance in editing software but would work very well, replacing the white paper described in this article.


Commercial link:
DotLineCorp White Balance Disks ($20)
I have not tried these products, but am somewhat interested.  On the other hand, a sheet of white paper works fairly well.  There are also inexpensive white balance lens caps.

Commercial link:
ExpoImaging ExpoDisk on Amazon and others ($100).  A lot of people use the lid from a Pringles Potato Chip can, claiming they get the same results.