"One of these days Alice…. straight to the Moon"

The Honeymooners is one of my favorite shows. Yes, I’m dating myself, what’s it to ya? As much as I’d like to talk about the Honeymooners, this post is not about the show.

Last month one of my friends came to dinner and brought his new Canon SX30 with him. He had been disappointed with the results when he attempted to take a picture of the full moon the night before and was wondering if it was him or the limitation of the camera.

I asked to see the pictures he took and what was disappointing about them. When he showed me the first one, I immediately blurted out "Metering Mode."

Over Exposed Full Moon

The pictures I was looking at were of a bright white disk. I might as well have been looking directly into a spotlight. What is the issue here?

Point & Shoot cameras have come a long way in the past decade or so. They have all kinds of features and programs that make taking a picture almost a breeze for anyone. They are very smart about evaluating a scene and adjusting the settings to give you the best possible picture (within the limits of the camera), but they do not replace the photographer and that is why manufacturers have added different modes to allow the photographer to override the automated features of the camera.

What modes the camera has depends on which camera you buy.  For instance my friend’s Canon SX30 gives you the ability to use it in fully automated mode to a fully manual mode where you set the aperture value, exposure speed, and ISO setting and anything in between.  Choose a camera based on how much control you need.

Many Point & Shoots today have the ability to change a metering mode. Metering refers to light metering which is a measurement of the light intensity in a scene. How the measurement is taken dictates the setting of the camera at the time of exposure when using any form of automated settings. After all, the camera is all about allowing light coming through the lens for a certain period of time to allow for the capture of detail in the scene. Too much light coming into the camera will overexpose the scene and will blow out the highlights. Similar to this picture of the moon that looks like a white disk. Too little light effectively reduces the detail in the shadow areas of a scene and might give you complete blackness in those areas. In you have a camera with different metering modes the likelihood is that you have three settings or more. The most common ones are:

• Evaluated metering
• Center-weighted metering
• Spot metering

When using your camera in fully automated mode, without overriding the metering mode, your camera is most likely using evaluated metering. Evaluated is a term used by Canon, different manufacturers use different terms for that mode; but all manufacturers use similar concepts of measuring light intensity for the scenes. For instance, in evaluated metering mode, the camera will divide the scene into multiple segments as defined by the manufacturer and the light intensity is measured in each of those segments, and each manufacturer has their own algorithm for coming up with the appropriate exposure based on those measurements. We would like to think that it is really an average of all, but it is not that simple and each manufacturer protects their algorithms and methods of evaluating the light – but basically it comes up to some compromise in order to allow the best exposure for the scene that the camera sees.

Centered-weighted metering is somewhat different in that only a portion of the scene – focused mostly on the center area – is evaluated for light intensity. That portion depends on the manufacturer again, but it may be somewhere around 50% – 60% depending on the manufacturer of that scene evaluation.

The final, the spot metering, constricts the measurement of light intensity to an even much smaller area of the scene, normally between 1% – 5% of the area. In Point and Shoots that will be right in the middle of your viewfinder.

What does this all mean to you as a photographer? As you can see from the white disk picture, using the camera default evaluated metering mode you are not left with a satisfactory image. Since taking a photo of the moon in a very dark sky, and since, in reality, you will not have detail in that black sky, you need to ensure that the camera reads the light intensity of the moon and not the background as not to over expose the scene. In this case, since the moon takes only a small portion of the sky (unless of course you have an ultra-telephoto lens), spot metering is the appropriate mode to allow the camera to appropriately set the exposure.

Properly Exposed Full Moon

Take a look at this picture and you can see how much detail you can see in the moon. Other areas you use spot metering for will be a backlit scene. For instance, where you have a sunset and you are attempting to get the picture of a person that is in front of that sunset. If you use the default setting, you’ll end up with an underexposure of the person, effectively making them a silhouette in the foreground of the photo. In this instance, you will want to use the spot metering mode and take the measurement of that person’s face or silhouette in order to get the necessary detail in the image.

Hope this helps!  Happy shooting! Let me know if you have any questions or need advice.