Tired of dull, gray snow scenes? Having trouble taking bright, white snow photographs? Here is what to know when shooting snow!
Early cameras did not have built in light meters. You either had to guess at the exposure based on previous tests or later using a handheld light meter. It was easier when using a flash bulb such as on a press camera you see used in the movies because the exposure with a flash bulb is based on distance – basically the time it takes for the light to bounce off the subject and come back to the camera.
Eventually light meters were included in the camera design. But the most important thing to remember about light meters is that are measuring the object they are pointed at and are trying to calculate the exposure to represent the subject at what is known as 18% gray.
As the majority of snapshot with cameras are people and assumed Caucasian or Asian skin tones, the camera manufactures assumed that most of the time photographers would want to expose for this 18% gray tone.
This means that every time you take a picture of something that is not 18% gray or in that range, the exposure is most likely to be over or under exposed.
Take a picture of a 18% gray wall and it will correctly expose as 18% gray. Take a picture of a white painted wall, white wedding dress or snow and it will come out underexposed or gray.
Take a photo of a black wall or a black frying pan and it will come out overexposed or gray instead of black.
This is why its important to understand how to use your exposure compensation controls on your camera to purposely under expose or over expose your scene to get the right exposure.
Over expose to get white snow, under expose to get true black scenes. You have to “fool” or “trick” your build in exposure meter to get the right settings.
Another method would be to shot a 18% gray card and then enter those setting into the camera in manual mode. Or use a light meter to take the ambient light measurements. Rather than metering reflected light, this setting on a hand held light meter measures the light falling on the scene.
Why 18% Gray? Is it really 18% or more like 12%? Does it really matter?
The story goes that Ansel Adams came up with the “18% gray” figure. Back in the hay day of film photography he was developing the zone system and needed to define a “middle gray”. It was a judgment call. Eventually, the idea caught on, but film and camera companies picked their own middle gray. It is a fun fact that your digital camera probably uses something more like 12% gray as middle gray.
Whatever the number, the idea behind middle gray is not that is “reflects 50% of the light”. Or even that “it is half way between absorbing all light (pure black) and reflecting all light (pure white)”. It has to do with your perception.
Your eyes are logarithmic detectors. That is, if a source gets brighter by a factor of 4, it will only seem brighter by a factor of 2 to you. If it increases by a factor of 32, it will only seem brighter by a factor of 5. If it increases in brightness by a factor of 128, it will only seem 7 times brighter to you.
The above are not the actual numbers. As you can imagine, measuring how bright things seem to people is very tricky, and varies from person to person. The important thing is that it is this weird logarithmic nature of your eyes that keeps middle gray from being 50%.
- How to use a gray card to determine exposure
Set your camera to manual shooting mode. Select the ISO and aperture you wish to use for your shot.
Set your camera’s metering mode to Spot Metering. This will allow the camera to read a very small area only, helpful if you only have a small gray card. You only want it to read the light off the reflector only, not the entire scene.
Set your focus point to single and choose the center one. Your camera will meter the same place it focuses.
Aim your camera at the gray card and press the shutter button part way down to take a reading. Looking in your viewfinder (eye piece) adjust the shutter speed until it gives you a reading of “0” (zero).
Take a test shot of the model (or subject) and the gray card similar to the one above. (You’ll be able to use this in part four below also.)
Review the histogram – you should have a perfect exposure with the gray card and all tones falling in the correct zones.