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Thursday, February 20, 2014

Canon Offers White Balance Tips When Photographing In Snow

Arctic fox in bright sunlight and reflecting snow

Polar bear cub in heavily overcast day on snow

* * * Read this post on how to protect photo gear in cold environments * * *

Photographing wildlife and people in snow is always a challenge. I was in Hudson Bay a few months ago on a shoot to photograph Arctic wildlife like Polar Bears and Arctic Foxes. You can visit my website to see more shots from my trips in the Arctic and sub Arctic.

Now, Canon Digital Learning Center has come out with an article offering white balance tips when photographing in snow. Below is an excerpt from their site :

"As photographers, our goal is to recreate the scene before us using both light and color. As advanced as digital cameras are these days, they don’t yet match the complexity of the human mind so we have to work with a few technical limitations when trying to record a scene as our eye sees it. Snow covered winter landscapes, in particular, can present some very specific challenges when it comes to getting accurate looking colors.

If you’ve ever looked at one of your winter images and thought that things look a little blue, then you’ve discovered one of the challenges of photographing snow: getting the right white balance or color temperature. White balance is a fundamental camera setting that adjusts color rendition to give a neutral appearance, without any obvious overall color tints or shifts. Cameras come with several White Balance presets (Daylight, Tungsten, Flash, etc.), but difficulties can arise when there are mixed light sources all adding their own color cast. In fact, it doesn’t even need to be a direct source either because all reflected light will have a color cast that’s dependent on the color of the object the light just bounced off of. If there are objects in your image (quite likely!) then you’ve got multiple color casts, in some way.

One measure of color in an image is Color Temperature. A simplified, non-technical description for photography purposes is that Color Temperature is a numerical scale, based on Degrees Kelvin, that defines the level of amber or blue in daylight and other light sources. Noontime sunlight is rated at about 5500 degrees Kelvin; warm, amber sources like sunsets or tungsten household bulbs can be 3000K or less; and scenes with excessive blue tonalities (like shaded areas on a clear, sunny day) can be anywhere from 7000K to 10000K. Most Canon EOS cameras offer a "K" white balance option, which can be a very precise way to pre-set white balance when shooting in daylight or tungsten illumination. (Please note that Kelvin WB is not available on EOS Rebel models.)

White balance presets are a good starting point, but they aren’t always perfect – the preset “Sunlight,” for example, sounds as though it would be perfect on a sunny day and it’s been standardized to a temperature of 5500K. But the reality is that sunlight color temperature varies based on time of day, atmospheric conditions, your altitude and many other factors. For my typical sunny snow images, I can end up using a White Balance that’s anywhere between 5000K and 9000K during what I would call “daytime.” If I were to include sunrise and sunset shoots, we’d be stretching the range from about 3000K to well north of 12000K. If you used standard White Balance presets during the “Golden Hour” (the first and last hour of the day’s sunlight), you could end up neutralizing that beautiful light that photographers are always lusting after. Presets should be looked at as a good starting point and an excellent way to learn more about the behavior of different light sources, but they are rarely a perfect answer.

Because most scenes contain a variety of color casts, there’s always going to be some compromise – that means that not all objects will be 100% accurate if we can only set a single temperature. Most of the time, in normal images, this compromise is imperceptible but the problem with winter images is that our brains know that snow it white!

If you look at a snowy scene, it’s likely to contain a lot of shadows caused by mountains and trees, for example. The snow in direct sunlight has a color cast that is one temperature, but the shadow has a vastly different temperature because it’s made up entirely of light that’s been bounced off other surrounding objects, such as the sky or snow itself. The human mind is incredibly powerful and because it knows that snow is white, it corrects our own vision of the scene to compensate for this. To us, snow always looks white. In the camera, though, we can only set one White Balance. Which is it to be?

If you set your camera to Auto White Balance (AWB), then you’re asking the camera to make that decision. In most cases, cameras these days have become good at measuring the variety of temperatures in a scene and creating an average. Every now and again when one cast is more predominant than the other, you’ll get the situation where your snowy images can look too blue. This will usually happen in a snowy image where there is a lot of shadow, but it can also look blue during daylight on a sunny day with blue skies when that color gets reflected in the snow.

How do I solve it? Firstly, I always opt to shoot in RAW because it gives you the option to adjust the White Balance later in your chosen editing software. I try and get it right in-camera when I can, but sometimes rapidly changing light makes it impractical. For example, if I’m hanging out of the side of a helicopter following a skier down a steep line in Alaska, then it’s simply not possible to be simultaneously tweaking White Balance. Another example would be in an uncontrolled situation like a sporting event where there is rapidly changing weather, typically moving clouds. In these situations, I set the camera to Auto White Balance and I use the “Eyedropper” tool in software like Canon’s Digital Photo Professional or Adobe Lightroom. The “Eyedropper” tool measures the temperature of one point in the image and sets the White Balance to that setting. As we know, if there are shadows and sunlight areas in the image, then these will be different temperatures so I usually pick a spot representative of the predominant situation in the scene. If it’s mostly shady, I’ll pick that. If it’s mostly direct sunlight with the odd shadow, I’ll pick the snow that’s in the direct light as long as the subject of the image is also in that predominant sector. It’s important that your subject looks accurately colored.

If the situation is much more controlled, like a commercial shoot where color accuracy of a product is of paramount importance, then I aim to get things right in-camera using a Custom White Balance. Readily available digital Gray Cards can be used for a test shot in your light and then set as the source of a Custom White Balance in-camera. Essentially, you’re telling the camera “this is a neutral color in this light.” Gray Cards, or other products such as the ExpoDisc, are relatively small and lightweight to carry around and can save you a lot of headaches. I’ll sometimes make use of a little product called the SpyderCube from Datacolor, as well. This is like a tiny gray card that you can include in a test shot so that you have an accurate neutral gray to use with the color picker later in your software. This works well for portraits in snow, but for action images, it’s not practical to always be in the spot where your athletes are about to be… I’m sure you can see why in some of these example photos!

In the end, sometimes there are compromises to be made when setting White Balance, just as there are with exposure when you choose where to add detail to the shadows at the expense of clipping your highlights. The best way to deal with it is to understand how it all works and why the images can sometimes look too blue in these tricky winter landscapes. If you don’t want to go so far as to set Custom White Balances but would rather not spend time adjusting them on the computer, then try the presets for “Cloudy” (~6500K) and “Shade” (~7500K). Light in the shade is much bluer, so the preset warms it up. If your winter images are looking blue, then this can be a quick fix to the problem. But be wary of this if you have large patches of snow in direct sunlight, as this will render the brighter patches too warm."

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