Matrix Metering, Smart Metering, evaluative metering – or whatever your favorite brand calls it – is amazingly good, fully capable of providing accurate exposures in many difficult lighting situations.
Modern evaluative camera metering systems use preset instructions in the camera’s computer brain, based on evaluations of thousands of images, to automatically compensate for a wide range of difficult lighting situations. This is true whether you are in full program auto or shooting manually but relying on the in-camera meter or any exposure mode in between.
With evaluative metering, the camera’s computer processor scans everything in the entire scene. The computer recognizes certain patterns of light and dark in the scene and compares those patterns with the instructions it has concerning thousands and thousands of similar patterns. Autofocus points may be factored in as well. It then chooses an exposure that should be correct for the scene.
Instead of merely averaging out the light and dark, it actively evaluates the specific photographic situation you are in and automatically compensates exposure settings to provide a properly exposed image. It’s the default metering mode for fully automatic camera operation.
Most of the major brands will have a similar icon either in an LCD display or a label next to a button or switch.
- Use evaluative metering when shooting fast action or in rapidly changing light conditions.
- For most situations, it is surprisingly accurate. Don’t just think of it as the beginner or snapshot metering mode.
Averaging or Center Weighted Averaging Mode
Sometimes though, you don’t want the camera to override your exposure measurement decisions. So, you can turn your camera metering setting to averaging. Often it is actually center-weighted averaging, giving the center of the frame more importance than the outer parts.
For many years, this was the default metering area mode. If you learned photography on manual focus 35mm film SLRs, this is probably the metering area mode you became very used to. It’s a good mode for most general purpose photography.
- Use for group portraits and head and shoulder portraits in any lighting other than strong backlighting.
- Also good for landscapes such as fall foliage.
Spot or Partial Area Mode
Some cameras also have spot metering or a mode that lets you take multiple spot readings to combine and average. Only a small portion of the scene is measured. For some of the major brands, it can be either a large spot (12 percent) also known as partial, or it could be a very small spot (one percent).
When you want the exposure to be based off of only a very small portion of the image, this metering mode is your best choice.
- In some cameras for professionals or advanced enthusiasts, the small spot for metering can be linked to a specific focus sensor point.
- For a subject lit by a spot light, this is the best meter area mode.
Camera Exposure Modes
Focus modes, metering modes, auto-exposure modes, drive modes, there sure are a lot of modes in our cameras. We just covered metering area modes, now let’s look at auto-exposure modes, since those are related to metering.
Manual (M) Mode
You are setting everything exposure-related on your own. Shutter speed, lens aperture (f-stop), and ISO are set by you and they will stay set that way until you change them.
- The built-in meter’s reading can be used or ignored.
- Ignore it if you are using a handheld meter or have a special technique or method in mind.
- Manual mode is the best mode for HDR photography or panoramas.
- Also use manual mode for astrophotography or other very long exposure situations.
Aperture Priority (Av) Mode
You set the lens f-stop and the camera decides the shutter speed to use based on the light conditions and whatever ISO you are using. This mode was the most popular automation during the big boom of exposure automation of the 60s, 70, and 80s, probably because it is simple to adapt to all sorts of lenses.
- Av mode is often the best mode of choice when using older lenses that don’t have any of the modern camera connections or when using lens mount adapters. As an example, this will allow automatic exposure when using a 60-year-old specialty portrait lens on a mirrorless digital camera.
- It is also the mode to use when depth of field is most important. Such as a small aperture (f/16) for maximum depth in a landscape or a wide aperture (f/2.8) for a portrait with only the person in focus.
Shutter Priority (Tv) Mode
You decide what shutter speed to use and the camera sets the aperture. This mode requires lenses to be matched to the camera’s controls, either by mechanical means or electronically.
- Use this mode when shooting action. Slow shutter speeds blur movement; fast shutter speeds freeze movement.
- Pan with a moving subject to create background blur.
- Keep camera still to create subject blur.
Program or Programmed (P) Mode
Both the f-stop and the shutter speed are controlled by the camera. The camera computer chip has a preprogrammed set of exposure combinations for a given light value. There are a lot of ways that current camera makers are doing program mode. Several allow user input to change what combinations of settings are used.
This is also the exposure mode you are in when you set your camera to that green dot full auto setting. Remember, that green dot auto mode takes control of just about everything in the camera – focus mode, meter mode, motor drive mode, exposure mode. You can’t change anything but the focal length of your zoom lens.
Exposure mode selector showing green dot auto mode. Photo by Bill McChesney
via Flickr Commons (CC BY 2.0)
Flash Automation (TTL and Other)
Manufacturers are giving photographers many options in how we expose our images with flashes or strobes.
One of the biggest improvements to flash photography came out in the late 1970s and early 1980s from several manufacturers: OTF TTL flash metering. TTL means through the lens, OTF stands for off the film plane. This metering method is widely used in current digital cameras from entry level to very high-end professional models.
A light reading sensor is placed inside the camera, either pointing at the sensor or film or pointing up at the back of the lens. The light coming into the camera during the flash exposure is measured. This is the most accurate way to meter when using flash.
- Some flash metering modes include focus distance calculation for completely balanced flash and ambient light exposures. Also known as automatic fill flash.
If your camera is in any of the exposure modes other than full auto mode, you can use this setting to override the meter reading for either more or less exposure. You do this by setting a value (-1, +2, etc…) for exposure compensation on a dial or in the camera menu.
This control is most commonly used for better control in challenging lighting and scene conditions, such as the high key or low key scenes highlighted earlier.
Take some time to experiment with your camera in different lighting conditions using all the exposure modes. Then note which situations yielded consistently over- or underexposed images. Use exposure compensation for those conditions in future photo shoots.
You Are In Control
When it comes to metering area modes, exposure modes, or what shutter speed, f-stop, or ISO to use, you are in control. What’s important is making good images.
Get the best possible exposure in-camera instead of having the “I can fix that in Photoshop” mindset. In other words, use post-processing to enhance your images, and quit trying to save a bad image (unless it’s the only photo you have of an important subject or event).
However you are using this art and craft of drawing with light, exposure settings and metering are an integral part of your imaging.
I urge you to try out some of these modes in your own cameras that you may not use regularly. Pick up an old light meter at an estate sale or your favorite local camera store and play around with it. Read the manual of your current equipment to see just what it can do. And join the PHLEARN Phamily to share your experiences and get helpful tips and feedback.