How To Measure Light With Your Camera

Measuring light in photography is an art as well as a science.  This combination of technical knowledge and artistic vision is essential to using creative exposure techniques and making better photos.

Combining the art and science of measuring light is used to establish a base reading for setting your exposure.  You can use this reading as a sample exposure given the amount of light that is available for you to capture with your camera.

Once you have your sample light reading, or base, you can use the components in the exposure equation to choose or manipulate your exposure settings to adjust the aperture, shutter speed, and/or the ISO.

Today, one of the most commonly used tools for getting your base reading is your camera’s built in light meter.  You can set your ISO then put the camera in auto exposure to get an initial reading.  With the camera in auto exposure the shutter speed and aperture will be chosen for you.

A more advanced way to use your camera’s build in light meter would be to use your aperture priority setting or your shutter speed priority setting.

You can get a base light meter reading in shutter priority by pre-selecting your shutter speed.  The camera will then adjust your f-stop or aperture.

If you use your aperture priority mode you can choose your f-stop and the camera will adjust your shutter speed.

Using the aperture or shutter priority modes is often preferable to using full auto mode for getting exposure readings.  This is because you will have control of two of the three components in the exposure equation.

Some camera models will allow you to get a light meter reading by simply doing a “half press”.  This is where you press the shutter button halfway down.  Always check your camera’s manual for specifics to your model.

The biggest issue is what you point your camera at to get your reading.  Rarely are we blessed to have a uniformly lit subject.  A brightly lit subject will give you very different readings than a darkly lit subject even in same light scenarios.  The sky is more brightly lit at sunset than the ground at the same time of day.  Pay attention to what you are pointing the camera at when you get your light meter reading.

Once you’ve got your initial readings you can then adjust to compensate for any creative exposure you need for that given scenario.  Perhaps your subject is a portrait that is backlit by the sun.  You’ll probably end up “blowing-out” the sky.  That’s okay.  The important thing to expose in most portraits is the face.

If you only rely on your camera’s metering and never really adjust you’ll only end up with “average” exposures.

This may be okay at times but can often lead to photos that are quite boring.

Example:

Your photographing buildings.  The sky is at sunset.  By pointing your camera at the sky to get a reading of the sunset’s exposure and re framing your camera to capture the building you’ll likely turn the buildings black in silhouette.  This adds a great dramatic flare to your photography when done with practice.

Many advanced digital cameras allow you to use a “spot” meter.  This give a light meter reading specif to the center 10% of your image.  Again, check your camera’s manual to see how to set this functionality in your camera.  You can use the spot meter to get very creative with your exposures by metering different parts of your subject, re-framing, then shooting.  You’ll see how the same scene can come out with different exposures.  Try this on shadowed areas, mid-tone areas, and lighter areas to see the full effect.

If the average light in the area you are photographing is close in tonal range you may not need to use any advanced exposure adjustments at all.

For most photos, however, this is a considerable range of tonal values and it’s up to you to take a light reading of the areas of the scene that are most important to your composition.  Spot metering really helps out in these situations.

Photograph Sunset over Old Mill by LittleRedCera

Popularity: 3% [?]

Related posts:

1. In Camera Light Meter
2. Finding the Right Creative Exposure
3. The Exposure Equation
4. Why Exposure Matters
5. What is Shutter Speed?