Pretty much as the title says here, this post is all about Metering. Metering is also known as exposure metering, digital metering and camera metering but, for us, we just call it metering. In a nutshell, metering is how your camera decides what exposure to set the scene at. It influences your camera’s settings to allow the scene to be well exposed, all things considered. Metering doesn’t always get it right, but it can help you out if you are using any automatic settings.
There is a video on this topic, that’s here:
This video was requested by Stephanie & Ida over in The Request Box but it does crop up regularly in the Critique Group and in the membership, so here we are. To go with the video above, I’ve popped a few words together below with some examples:
How does metering work?
What the camera is doing is it is trying to balance the scene so that the average highlight is 18% grey. In simple scenes this is usually correct – you will not have blown highlights or clipped shadows. However, in complex or contrasty scenes, you’ll often find the metering doesn’t prioritise areas of the scene that you want to prioritise. That’s where metering modes and exposure compensation come in.
It is worth noting that metering only ever matters if you have something set to auto. Aperture priority, auto ISO or full auto will all have a setting that the camera decides itself – that uses metering. If you use manual mode with nothing automatic at all, metering doesn’t matter, it makes zero difference and it will not affect your exposure.
What are metering modes?
Metering modes are there to allow you to tell the camera to prioritise a specific area of the scene when it comes to exposure decisions. There are 3 core metering modes and a few new, model-specific ones. We’ll cover the main 3 here:
1. Matrix / Scene
This mode is usually set up automatically on the camera because it’s the most widely used for non-contrasty, evenly lit scenes. It uses all of the pixels in the scene to decide what the right exposure will be and it pulls an average to place on the settings. It’s kind of like the catch-all. It doesn’t prioritise anything specific.
This mode is a good one to use if you are just starting out and getting used to metering, especially if you are working with a super dark or super light subject (remember to check out exposure compensation though!) because it uses the central area of the image as its priority. This means that if you put your subject in the centre of the scene – something that honestly, I would not recommend, this is why – you should be fine with the metered average that comes in because there is at least partial emphasis on the subject, balances to other things around that central area.
The most specific of the metering modes, spot metering uses a very small area in the image to decide the exposure. Although this seems like the best option, because it is the most specific, it can work against you. For example, if you are photographing a black dog, using spot metering will cause the entire scene to be overexposed as the camera tries to turn that black dot into 18% grey. This is where exposure compensation and exposure lock come into play – it separated the beginner meterers from the expert meterers.
What is exposure compensation?
I’m so glad you asked! Exposure compensation is you having your say over the metering decision that the camera has made. Essentially, you can override the decided exposure with stop increments. Stops are just measures of light, so don’t panic about that. All you need to know is do you want the exposure to be lighter (move the exposure compensation towards the + side) or darker (move the exposure compensation towards the – side).
What if this is too much effort and you don’t have time to faff around with +/- decisions in the middle of a shoot? Well, say hello to Exposure Lock.
What is exposure lock or A/E Lock (also AE Lock)?
Now we’re getting into complex territory but honestly, exposure lock is very straightforward. Now, if you use back-button focus then you might need to reassign some buttons because often AE Lock and AF ON are the same button. Buttons assigned, exposure lock is exactly as it sounds, you get the camera to meter on something that isn’t super contrasty and then hold down that AE Lock button. With the button pressed, your camera will not re-meter until the button is released.
This means that you can take a centre weighted meter and then recompose for a better composition before focussing and shooting. It also means that you can quickly save highlights in a contrasty scene by metering on them before recomposing to shoot the shot.
If all of this sounds like WAY too much effort, you’re kind of right. We shoot here on manual mode so we decide every element of the exposure triangle. If you want to know more about that, read this post.