Introduction to White Balance for Digital Camera Users (Part III): Gray Card or White Card?

In the last week I received many emails asking which is better for measuring white balance accurately via a digital camera, a white card or a gray card, so I'm adding an unexpected Part III to my series on White Balance. (Part I, Part II)

Without knowing it, they've asked a question which has an technical answer, though not one they're expecting, and an unexpected practical answer too.

Let's go back to Part I of the series and review what white balance is:

"White balance is the process of adjusting color casts, so that objects which appear white to human eyes/brains are rendered white in the photograph by the camera."

To put it more simply, photographers set a digital camera's white balance to get the colors in images “right,” where the images' colors are what photographers' brains tell them their eyes are seeing.

Introduction to White Balance for Digital Camera Users (Part II)

Last week, in Part I, I discussed the concept of white balance and defined it. The general idea of white balance is to get objects which appear white to human eyes/brains to be rendered white in your images, so the rest of the colors will render properly as well.

I also discussed the important concept that sometimes, things we consider to be “white” aren't always white when we look at them, and that it's not wrong to ensure they don't look white in our images. During the “golden hours,” for example, white can appear “golden.” At sunset white buildings can take on red and golden hues.

This week I'm going to discuss the practical side of getting your white balance “right,” or at least as “right” as you can get it, so the colors in your saved image are rendered as you saw them.

It's winter. It's snowing . . . blue?

If you live in the northeastern US, the weather this past weekend ensured you knew it was winter. The snow came down, and some areas got as much as a couple of feet.

Many went out in the last few days to make photographs of snow scenes, only to review the photos and see blue or gray snow.

Unfortunately, digital cameras aren't as good as the combination of our eyes and brains, which are fantastic at color and contrast correction and have a large dynamic range. Whether we see snow in the sun, or shade, or even at night, unless the light illuminating the snow is colored, we see the snow as white.

Cameras don't see the same way we do. They can be fooled by blue skies or shady conditions for snow scenes. The problem is, in snow conditions, the camera often can't set the image's white balance correctly. This is even true with expensive DSLR cameras.

Photographing Sacred Spaces

When we travel we certainly see and often visit churches, temples, mosques, synagogues, and other religious shrines. Many contain some of the world’s great artwork. Many are architectural gems unto themselves. Many have extensive grounds. Many are important for their history, or their part in historic events.

Some are the center of their town’s or city’s culture, and attract visitors from across their region, country, and some attract visitors from across the world.

Often we find shops, vendors, and other places supporting the sacred space. That means many photo opportunities besides the place of worship itself, and those of its grounds and interior.

Gaining access to a place considered sacred by those who maintain and belong to it, brings responsibility to behave with sensitivity to the place of worship itself, those who worship in it, and those responsible for running it. The building, grounds, and the people must be respected.

HDR (High Dynamic Range Imaging): An Introduction

High dynamic range imaging (HDR) is a set of techniques which allows a photographer to produce a photograph displaying a greater dynamic range of luminances between light and dark areas, of  the scene to be photographed, than normal digital imaging. The idea behind HDR is to be able to accurately represent the wide range of light intensity levels found in the real world ranging from direct sunlight to shadows.

OK, so that’s what HDR is, but what we’re really seeing when we see an HDR image on a monitor, or in an HDR print, is a tone-mapped image of an HDR composite image.

Tone mapping is a technique used to process an image where we map a set of colors to an alternate set, to approximate the appearance of HDR images in media with a limited dynamic range, such as computer monitors, projectors, and printers. Each of these devices, and our digital cameras have a limited dynamic range which is inadequate to reproduce the entire range of light intensities present in many natural scenes which the human eye can discern.

In HDR/Tone Mapping the problem of contrast reduction from the scene to what can actually be displayed is handled, while preserving the image’s details and general color appearance.

So that’s the technical definition, but if you’re not familiar with HDR, I know you’re asking what the heck does that mean.

We often, as photographers, especially on bright days, come across a scene we’d like to photograph which has light intensities ranging from dark shadow to very bright whites. The photograph above is an HDR rendering of Independence Hall in Philadelphia, PA. Please note in the photo, that throughout the range of luminances (light intensities) the scene’s detail is preserved, from dark through light.

Take a look on the right. The three photos you see show the range of luminances which make up the HDR composite photo at the top of this article. In each photo, some detail has been lost.

When creating the final photo, I used the three photos on the right, plus two more, one exposed between the dark and center exposures, and one between the center and light exposures.

In order to create the five exposures I put my DSLR on a tripod and bracketed the exposure. I started with an exposure for the brightest light in the scene and kept increasing the exposure by decreasing shutter speed, until I had the right exposure for the darkest part of the scene.

The f/stop and iso remained constant for the photos which were taken within the span of just a few seconds. I set my white balance manually to the correct color temperature of the scene using an ExpoDisc.

By making these exposures, each one keeps the scene's detail for which the exposure was made, from dark to light.

To get the best results from your HDR processing, your exposure sequence must include photos which correctly expose highlights, and photos which correctly expose shadows. Exposing the shadows properly is especially important to avoid noise showing in the processed HDR image.

Then it’s off to the digital darkroom. I’m currently using Adobe Photoshop CS4 Extended for my general photograph editing and retouching. For HDR work, I use Photomatix Pro from HDRsoft, which integrates with Photoshop. I use the stand alone version of Photomatix, not the Photoshop plug-in, as it’s more powerful.

There are two steps involved in creating and processing HDR images:

In step 1 the software merges your photos taken under different exposure settings into a single 32-bit HDR image. Because of its high dynamic range, the 32-bit HDR image will not display properly on conventional monitors.

In step 2 the software processes the 32-bit HDR image via its Tone Mapping tool. Tone Mapping will reveal the dynamic range captured in the HDR image and produce an image that can be properly displayed on conventional monitors and can be properly printed.

Once the HDR/Tone Mapping processing is complete, the composite photo is ready for final editing in Photoshop.

You can surmise from the 3 photos on the right, the luminosity range limit of the DSLR’s sensor. Clearly the range of luminosity in the scene is well beyond the capability of the camera’s sensor. It’s clear that without using HDR to create the photograph of Independence Hall with such a large range from dark shadow to bright white in bright sunlight, the photo could not include all the detail of each tonal area of the scene which our eyes see.

Without the use of HDR, I would have had to use the middle exposure, which isn’t a bad snapshot, but doesn’t include the richness of the final composite photograph.

Museum Photography: Ten Tips

If you’re like me, you enjoy traveling to new and interesting cities. One of the wonderful things great cities have to offer is the chance to view and experience outstanding and occasionally extraordinary art, and sometimes you have the chance to photograph it.

Often cities also have natural history, science and other museums dedicated to some industry or sport, or other specialized subject, such as the Smithsonian Air and Space Museum’s aircraft and space vehicles. All can have great photographic opportunities.

Here are some tips for you, for museum photography.

• To start, you’ve got to know the museum’s ground rules. You need to determine if photography, in the museum and on its grounds, is permitted. While most museums do permit some photography, often with limitations, such as no flash photography, there are still many museums in the world which ban photography all together.


• Even if there are “No Photography” signs as you enter the museum, it won’t do any harm to ask at the information desk whether the signs mean no photography whatsoever, or just no flash photography. I’ve been pleasantly surprised many times, especially in Europe, to find they just want to prevent all flash photography, as the light from many close-up electronic flashes can damage some art work, and flashes can be very disconcerting to museum visitors.


• If photography is forbidden, put your camera in its bag. Don’t try to sneak in any photographs. Don’t be the “ugly” tourist.


• If it’s only flash photography that’s forbidden, don’t try slipping in a few flash photographs. If enough people do that, it might eventually move the museum to ban photography all together, taking away the privilege for everyone because of your thoughtlessness. If you have a separate flash, put it away. If you have a built-in flash, turn it off. (If you’re not sure how to turn it off, either ask a teenager how to do it, or put your camera away.)


• The light level at many museums often means you need to open your lens, slow down your shutter speed, and/or use a high iso setting in your digital camera, or use high speed film. If you could use a monopod or tripod, that would certainly help combat those conditions and permit a sharp clear photograph, however, tripods and monopods are rarely permitted to be used in a museum, as they interfere with visitors’ movement. If you have a tripod or monopod, ask if you’re permitted to use them, before entering the museum. At a tour of Winterthur last month, I brought my tripod for outdoor garden photos. When I toured the museum itself, even though it was in a case, I was required to check my tripod. Lenses and cameras with “image stabilization” or “vibration reduction” are extremely helpful in museums.


• Even at some travel sites to which everyone goes solely to take photos, tripods and monopods may be prohibited. Due to the crowded conditions no tripods and monopods are permitted on the observation deck of the Empire State Building in New York City.


• Respect the art and respect fellow museum visitors. Many museums have ropes or some kind of barricade preventing you from getting to close to an especially popular exhibit or piece of art, such as the Mona Lisa in the Louvre in Paris, but usually there’s nothing to prevent you from getting close. Even if you can get close, respect the art and the others viewing it by not monopolizing the space near the art. Let everyone have a chance.


• The museum’s collection might not be the only thing worthwhile viewing there. Sometimes the museum itself is spectacular. Parts of the Louvre in Paris, and the Pennsylvania Academy of the Fine Arts in Philadelphia have amazing exterior and interior architecture. The photograph on the right was taken at the Louvre. It’s not a painting or even a mosaic. It’s a ceiling of one of the galleries at the Louvre and a magnificent work of art itself.


• If you’re using an SLR or DSLR, don’t forget to bring a wide angle or wide angle zoom lens. It’s often needed in a museum for photographs of the museum itself or some larger sculptures or other exhibits.


• Most lighting in museums consists of artificial light or a combination of artificial and natural light. As a result, the automatic white balance setting on your digital camera may not produce accurate results. You may be better off manually setting your white balance. To help you achieve the correct white balance, if you can create a custom setting for it in your digital camera, consider using a WhiBal card, or if you have a DSLR, and Expo Disc to assist getting the correct white balance setting. I have used both and consider them excellent products.