Over the last two weekends Andrew and I have been presenting our Digital Photography 101 course.
One of the topics which a lot of people ask about is metering so with that in mind, here is a replay of an blog post I posted about a year or so ago.
For many new photographers, and quite a few not so new photographers, metering is one of the most difficult photographic terms to wrap their head around.
The short version is that the metering mode you choose will affect how the camera calculates the exposure of an image.
These days most cameras are very good at calculating the exposure of a scene but there are still times when you might have to help it out a little. You need to ‘tell’ your camera how to expose the scene, or more correctly, you need to tell the camera which parts of the scene to take into account when calculating the exposure.
It is at this point that a lot of people start getting a bit nervous.
Not necessary! Just hang on and bear with me.
Before we have a look at the different metering modes available to you it is worth just reminding ourselves that the goal of the metering exercise is to calculate the exposure of an image. In simplified terms, exposure refers to how light or dark an image is rendered.
Right. Moving on.
I was trying to work out an easy analogy to explain the way a camera sees and shows different scenes when I found an much easier way.
You see, the iPhone does not have a whole bunch of metering settings so is will always use the entire scene you are photographing to calculate the final exposure of the image. (You should go and try this with your phone as well!)
I shot this image this morning, and purposefully placed the horizon in the middle of the frame.
In order to render this image, the iPhone camera would have taken the very bright areas, the sky around the sun, and and the very dark areas, the black foreground, into account.
If you look closely at the foreground you can just (almost) make out the wooden fence. The phone camera, and this goes for large DSLR cameras as well, cannot see and render the entire range of tones, from pure white to pure black, so it averages everything out. It makes the brights a bit darker and the darks a bit lighter.
In the above image the camera therefore used the entire scene to calculate the final exposure. This is called Matrix or Evaluative metering.
Now, if my goal was to show the detail in the wooden fence and rest of the dark foreground I simply tilt my phone down, thereby removing a lot of the bright sky and sun from the scene. This will result in the camera using the dark areas to calculate the exposure and therefore exposure for the dark areas.
Now you can see the details in the foreground.
What the camera did was to expose for the darks, thereby making them lighter when compared to the first image and making them the focus, from an exposure point of view, of the image.
This will result in the light areas in the scene also being made lighter and blowing it out completely by loosing all the details in these areas.
Still with me?
So, for most scenes where there are not too many very bright or very dark scenes in your frame you should be able to get away with matrix / evaluative metering.
It is when there are large bright or dark areas in the scene that you might have to use either centre weighted or spot metering to make sure that your subject is correctly exposed.
The above three symbols show evaluative, centre-weighted and spot metering options like you might find them on your camera. Yes, they differ from make to make so check your camera manual.
Keeping all the above in mind, let’s take a quick look at each of the metering options individually.
Evaluative / Matrix Metering
This is the default setting where the camera utilizes the entire scene to calculate the exposure of your image.
In the picture above the white, which covers almost the entire frame, shows the area which the camera will use to calculate the exposure of your image. This is how my iPhone calculated the exposure of the images at the top of the post.
These days most cameras will do a pretty good job of calculating the exposure but when you are faced with difficult lighting conditions this metering mode will influence your image by making
- the very dark areas lighter
- the very light areas darker
This is due to the camera censor’s inability to deal with the full range of tones, from pure white (very bright) to pure black (very dark) areas.
Example of Evaluative Metering
The image below consists of very even tones throughout the entire image. There are no large areas in the image that will confuse the camera so evaluative metering should do the trick.
In the image at the bottom you can see the white area that the camera would have used, had it been set to evaluative / matrix metering, to calculate the exposure in a scene like this
Centre Weighted Metering
This metering mode gives priority to the center portion of the photograph, but might still take the surrounding areas of the image into consideration.
In the picture above the white area now covers about 20% of the entire frame, depending on camera make, and is the area which the camera will use to calculate the exposure of your image.
This setting can be used when your subject, which you want to expose correctly, is in the middle of the photograph in which there are a few very bright or very dark areas. By metering off the subject, which is in the middle of the frame, the subject is not affected by the exposure of the background which could, for example, be much darker or lighter than the subject
Example of Centre Weighted Metering
The harsh sky in the background could have affected the final exposure of the scene. By using centre weighted metering, as shown by the white area, the camera calculated the exposure without taking the bright background into account and therefore the elephant was exposed correctly. The spin off is that the sky is slightly overexposed but that’s ok as it is not a part of the story in this image.
Spot / Partial Metering
This type of metering calculates the exposure of your image by utilizing a very small area in the middle of the frame.
In the picture above the white area now covers a very small area in the middle of the frame. Depending on your camera make this could be as small as 2% of the entire frame. When you use spot metering, this small area is used to calculate the exposure of your final image
This is helpful when you are photographing back-lit subjects or subjects where the background is a lot lighter or darker than the subject.
Use this metering mode when you have a very specific area of the photograph that you wish the exposure to be based upon. Remember that this might result in your background, which has not been taken into account during the metering process, being very over or underexposed.
Example of Spot Metering
The white area below shows that the camera was asked to only take the leopards head into account when calculating exposure. If the whole frame was included in the exposure calculation the image would have been rendered very differently as the camera would have tried to include all the very dark areas in the calculation.
Right. You still with me? Any of this making sense?
Let me try to summarize:
- Metering is how your camera calculates the exposure in a frame.
- If you have a very even-toned image use matrix / evaluative metering.
- If you have a scene with more than 30% very dark or light areas use centre-weighted metering
- If your background is very light or very dark, and takes up most of the frame, use spot metering.
- If you have a a tricky mix of light and dark areas use spot metering off your subject.
- You should get away with matrix / evaluative metering 90% of the time.
- For creative exposures try and play with spot metering.
So there you go.
A basic look at metering which I hope you will be able to help you somewhere along the line.
If you have any questions, comments or would like to add to this post please feel free to comment below!
Until next time.
Gerry van der Walt
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