Reconciling Mixed White Balance Scenarios

Setting the white balance (WB) of your camera correctly basically boils down to a couple-or-three clicks through your camera’s set-up menu and a few moments of your time. Depending on your needs or mindset, you can adjust your camera’s WB settings by dialing in a specific Kelvin rating (°K) or by adjusting the Scene Mode to whatever setting comes closest to the scene you plan on photographing, i.e., Daylight, Cloudy, Tungsten, Open Shade, Cool Fluorescent, Warm Fluorescent, etc.

For more critical applications, most digicams allow you the ability to set a custom WB using a gray card, an ExpoDisc, or similar WB calibration device.  And for most government work and snap-shooting needs, almost every digital camera has an Auto WB mode, which under “normal” lighting conditions, is often adequate. 

Achieving proper WB starts getting tricky when your subject and background are illuminated by spectrally mismatched light sources, a good example being a fluorescent or tungsten-lit office space with daylight spilling through the windows. In these cases choices have to be made, and the best place to start is identifying the dominant light source of the overall scene. From there it’s a matter of modifying the color balance of the secondary light source(s) to match the WB of the primary light source.

All photos in this article © Allan Weitz, 2011

In this photograph, which was taken in a fluorescent-lit workshop, the camera was set to Daylight and my subject was lit with a 600/Ws monoblock flash head aimed through a small circular softbox. By dragging the shutter speed I was able to take advantage of the daylight streaming through the windows that (thankfully) lined the length of the shop on both sides. To dampen the residual greenish cast caused by the ambient fluorescence I dialed down the saturation levels in the green channel of the image file in Photoshop. The resulting photograph has a natural, real-life feel and faithfully rendered flesh tones.

In the case of fluorescent lamps, which are spectrally red deficient, if you set your camera to Fluorescent, the portions of the scene you are photographing that are lit solely by the overhead fluorescent lights will be rendered correctly. However, the portions of the scene with daylight spilling onto them will have varying degrees of a magenta cast, depending on how much daylight is straying into the image area.

When shooting film or video, the most efficient method of neutralizing the magenta bias of the daylight portion of the exposure is to cover the windows with sheets or rolls of green-tinted correction filters such as Roscolux Plusgreen gels, which are available in full to 1/8^th-strength correction. Full Plusgreen filtration, which approximates the hue and density of a 30G “cc” filter, is strong enough to shift “average” fluorescent tubes to an acceptable approximation of daylight.

Similarly, interiors lit with tungsten lighting fixtures, which are deficient in the blue portion of the visual spectrum and have a yellow bias, can be neutralized by setting the camera’s WB to Tungsten. In these cases any daylight spilling into the scene will be rendered with varying degrees of a bluish cast with details beyond the window rendered with a heavier, dusk-like blue cast. Likewise, you can set the camera to a Daylight WB setting, which will render everything bathed in window light correctly while portions of the scene further from the windows becoming progressively warmer-looking as the tungsten lamps begin to dominate the field of view.

To correct any blue-tinged daylight straying through the windows, cover the windows with rolls or sheets of orange gels (#85 or Full CTS), which brings the daylight closer in line with the 3200/3400° Kelvin rating of the dominant tungsten lighting.

Aesthetically speaking, the big difference between the abovementioned scenarios is that the warmth of the tungsten lighting fixtures is more pleasing to the eye compared to the greenish cast of the fluorescent fixtures.

Note: If the light coming through the window is the dominant source of illumination, you can often set your camera to Daylight and be done with it, but this is a generalization and as a course of action must be taken on a case-by-case basis.

Our brains do a very good job of compensating for these green/magenta and blue/yellow color-balance discrepancies, but our cameras, lacking the advanced microprocessors found in our brains, fall short when trying to reconcile extreme differences of color balance within a common scene.

This restaurant was lit on three sides by a wash of direct and indirect window light and overhead tungsten lamps. Using daylight as the default WB setting, I used a combination of the ambient window light and electronic fill flash in the foreground from three medium-sized light banks as the base of the exposure while taking full advantage of the warm glow of the recessed incandescent lighting emanating from the grid-like overhead structure.

Note: The color rendition of tungsten and fluorescent lamps varies greatly. As a result, the Tungsten and Fluorescent settings on your camera may or may not render clean color. In these cases it’s recommended to set a custom WB according to the instructions in your camera’s manual with a gray card, an ExpoDisc, or similar WB calibration device. Auto White Balance (AWB) is a setting found on almost all digital cameras; depending on the make and model of your camera, may or may not render the color characteristics of the ambient light on your subject.

A few quick comparison shots captured using the camera’s AWB mode and Fluorescent/Tungsten WB mode(s) should get you in the ballpark. Regardless of your final WB choice, always keep in mind when shooting under mixed light sources: RAW files are your best friends.

A simple solution often employed by architectural photographers shooting interior scenes involving mixed lighting scenarios involving widow light is to schedule these assignments for the evening hours. While such scheduling can be irritating for those who prefer to clock out at five, it greatly simplifies the workflow. But this isn’t always possible, especially when the view out the window is a key selling point of the space. In such cases, the interior portions of the scene can be lit with flash or HMIs, both of which are daylight balanced.

Note: Color temperature is extremely difficult to eyeball, and as such, when shooting under mixed lighting it’s a good idea to follow one or more of the following recommendations.

1. Use a color temperature meter, which unlike a conventional light meter that reads the volume of light, measures the color temperature of the ambient and/or flash exposure and indicates the precise degree of filtration needed to neutralize the color balance. Color temperature meters are notably more expensive than conventional light meters, but if you shoot under mixed lighting regularly, they can greatly reduce the amount of testing time required when shooting under mixed lighting conditions.
2. Create a custom WB using a gray card to establish a neutral base. You can also set a custom WB using third-party devices such as ExpoDisc.
3. Shoot RAW files, which can be color-corrected post capture, globally or in layers.
4. If your camera has a WB Bracketing mode, this is a good time to use it, especially if you’re only shooting JPEGs. Having a set of WB-bracketed images on hand captured within tight, consistent parameters can prove to be extremely useful if you plan on working in layers later on, in post-production.

Note: When using gels on tungsten light sources, check the heat ratings of the gels you plan on using because tungsten lights can easily produce combustible levels of heat in a short period of time.

It’s also worth noting that even WB levels are not always necessary or even desirable. A good example would be the warm glow of tungsten lamps in a room predominantly lit by window light. In many cases, the warmth of the lamps can create a more inviting atmosphere for the overall dynamics of the image, as illustrated in the above photograph of the restaurant interior.

When shooting room interiors containing window light and tungsten and/or incandescent light fixtures, another simple trick is to replace all of the incandescent lamps with small wireless strobes that screw into and are powered by standard light fixtures, which can be triggered simultaneously along with any main flash including the one built into your camera. The result is natural-looking lighting with even color balance.

Dawn and dusk are often the best times to photograph building exteriors, and here too, you are inevitably dealing with mixed light sources. In the photograph above, the exterior lights are tungsten-based, resulting in a warm, inviting glow that plays off well against the afterglow of the cloud-free sunset. Had the exterior lights been fluorescent, the warm yellow glow would be a more ghoulish green. In these cases it’s advisable to shoot RAW and create a new image file composed of a color-corrected building exterior layered against the same graduated dusk sky as seen above. Regardless of whether the building is illuminated by tungsten or fluorescent light, use daylight as your default WB, especially if you’re limited to JPEGs.