The following question came to me recently, so I thought I’d answer it here:
Q: I have a few questions/misunderstandings about white balance (WB) and how to set it as close as possible in camera settings. I know it may be difficult to set perfect WB, but setting a proper WB can be confusing for a beginner like myself, I’d like to have a sound understanding of setting WB in camera in any given situation, but especially while using flash units. You briefly discuss this in your 100% Reliable Flash Photography eBook. I know post-processing can provide corrections with Raw files, however I haven’t crossed that bridge yet and would rather get a firm grasp on WB in camera settings to minimize post work when the time comes.
1) Can you explain in detail how to setup WB settings in camera, with mixed lighting conditions? Example, in a home studio with CFL/incandescent bulbs as ambient sources in the room and flash units as the main/key light using shoot-through umbrella and possibly adding other flash for background fill, hair fill, rim light etc. How should I properly set WB in these situations?
2) I hear/read about gray cards and white cards, and also reference targets. Can you cover this in more detail and explain how these would be used in different environments and when should they be used (i.e. are these protocols/tools used in studios, portraiture work and in every photo session/environment)?
A: The goal of achieving a good white balance (WB) is to downplay or eliminate unwanted color casts in your images. If you make sure white objects appear white, then all the other colors in the image should be accurate, so the thinking goes. And most of the time, that’s how it works.
What Causes Color Casts?
Light comes in different colors (or color temperatures that can be measured on the Kelvin scale as shown in Figure 1). There are warmer colors like candle light and tungsten light, which can create an orange color cast in your images. Colder color casts can appear under shady or cloudy conditions. It can be hard for us to recognize these color casts in a given environment because our eyes and brains compensate for them, but our cameras capture those color casts and we can certainly see them in photographs. You can compensate for these color casts in you images by making WB adjustments either prior to taking pictures, or during post-processing. In Figure 2, you can see the various color casts that appear under ambient daylight/shady conditions, using different WB settings. Figure 3 shows a similar sequence under tungsten lighting.
As you can see, your camera’s Auto WB (AWB) setting can be quite good at determining proper WB given enough information. You’ll notice using the Tungsten WB setting in daylight conditions will result in extra blue, while the daylight setting in tungsten light results in a more orange cast. This demonstrates how the camera adjusts colors to compensate for various casts; use the wrong compensation and the camera itself will create the color cast.
Figure 1. Simplified view of the visible color spectrum and where the Kelvin numbers fall in the range of colors, warmer to cooler.
Figure 2. Daylight/Shade shots taken using various WB settings.
Figure 3. Tungsten lighting shots taken using various WB settings.
Setting WB In-Camera
Although WB adjustments can be made to your image during post-processing, you can try to establish a good WB before you actually take a picture; your camera has controls for setting WB (see Figure 4). Generally, they are:
- AWB (Automatic White Balance): This allows your camera determine WB based on ambient light conditions and/or if the use of flash is detected.
- Standard Settings: You can select one of the standard settings based on general lighting conditions. These include settings for Tungsten, Fluorescent, Cloudy/Shade, Daylight, etc.
- Custom Settings: Under the lighting conditions you’ll be shooting in, take a photo of a white or neutral gray card. A feature on your camera can use that image to calibrate and save a specific WB setting that will be used for the photos you’ll shoot under those same lighting conditions.
- Kelvin Setting: This allows you to manually select a color temperature based on the Kelvin scale.
Figure 4. White balance setting icons on my Canon 7D.
Correcting for WB in Post-Processing
You can make WB adjustments to your image during post-processing using tools found in software like Adobe Lightroom. This can be as easy as clicking on a neutral color in an image, allowing the software to make the correct adjustments to achieve proper WB. Below, is a photo taken in a NYC subway station under fluorescent lights (see Figure 5). The shot was taken with the camera set to AWB. The first image shows what it looked like in Lightroom using the settings applied by the camera (“As Shot”). The second shows the same image after applying Lightroom’s default setting for Fluorescent WB adjustment. The third shows the WB adjustment after I used the WB adjustment eyedropper to select one of the neutral gray areas on the color chart. It was this last method that gave me the most accurate colors.
Figure 5. AWB in-camera and Lightroom WB adjustments in post.
Mixed Lighting, Mixed Color Casts
Adjusting for a color cast is pretty straight-forward, but a problem might arise if you’re using mixed lighting (lights of different color temperatures as shown in Figure 6). Your camera can only compensate for one color cast at a time. So when you have more than one potentially unwanted color cast in a scene, you have a problem.
Figure 6. Mixed lighting; tungsten lamp and flash for the subject.
I have to admit that I really don’t worry about this kind of thing very much. My approach is to simply get a decent WB setting in camera for the image in general; really I just want to make sure the subject isn’t affected by a color cast. If I’m shooting with flash, and there are tungsten lights in the background (maybe as part of the environment; candles, fireplace, accent lights, etc.), those might look just fine appearing as warmer colors and lights. In some cases, it might look natural to see these warmer colors somewhat reflecting off the subject. If I don’t like some of the colors appearing in an image, I will often selectively adjust them in post as shown in Figure 7. This means, I’ll adjust the colors to parts of the image as I see fit.
Figure 7. In the image above, there were at least three different types of light sources in the scene. My flash, daylight, tungsten, and what I assume is some sort of halogen in the background. I made selective (area) adjustments to get the colors the way I wanted them (top photo). However, with only a broad adjustment to the whole image, I would have had to pick one area to correct for and the others would have shifted accordingly (bottom image).
Another approach is to correct or balance the colors coming off various light sources in a scene. You can do this with gels (see Figure 8). As an example, if you have a scene with predominately tungsten lighting (creates an orange cast), you can attach a Color Temperature Orange (CTO) gel/filter to your flash so that the light emitted from it is similar to what’s in the rest of the scene. Since all lights are now producing the same color cast, a simple WB for tungsten (in-camera or during post) will likely do the trick.
Figure 8. Color filter over flash to match tungsten lighting in the scene.
Gray Cards and Color Reference Charts
As I mentioned earlier, a neutral gray card (often called an 18% gray card, but I’m not really sure about the accuracy of that term) can be used by the camera or post-processing software to help make WB adjustments. You’ll have to consult your camera’s manual if you want to learn how to do custom WB on your camera. In post-processing, any area of neutral color can be used to quickly, automatically make WB adjustments.
Some color reference charts have specially produced color swatches that can help you get very accurate color matching results. I’ve been using the DKC-PRO Digital Kolor Card – Pro 5×7 (see Figure 10) because it’s small enough to fit into my backpack and has a large series of swatches that cover a range of white to black in 6 steps. On the back, is a large offset printed neutral gray card that does the job.
You can use a simple gray card or reference chart under any lighting conditions, or anytime you’d like to be able to get a good WB or have a known color reference in your images.
Figure 9. Digital Kolor Card – Pro 5×7.
But that’s just the beginning of the story
These are all tools that are helpful for achieving correct color. If you’re aiming for accurate color, it’s important that your monitor be correctly calibrated, too. Without that, your colors might be way off, and once you get the colors in a shot looking correct on your screen, they might actually be more blue or orange on other screens, or in the prints you order.
There are different schools of thought on reproducing “correct” color. I mean, sometimes it’s necessary to reproduce colors as accurately as possible, but other times, not so much. Even if you manage to get those colors right, who’s to say they’ll look right on someone else’s monitor, or once they come back from the printer? Even if a print depicts the colors accurately under white light, those colors are going to look very different when viewed under tungsten light. So, I really don’t worry about that kind of thing very much, unless color accuracy is critical. I just make sure the colors look good to me, and convey the feeling I want. I’ll even throw in a color cast sometimes if I think it looks good.