I don’t like to give dramatic commandments in photography or for techniques of photography. “Do this, always, in this circumstance,” just makes me, personally, want to try the opposite. However, there is value in understanding the ‘why’ behind conventional wisdom; once you understand how that wisdom became conventional in the first place (why the ‘rules’ are the rules) you can then better understand when, why and how to break them.
All that said, I’d like to offer some thoughts on metering that have been bouncing around my head for the last few months as I’ve been shooting. This topic came to the fore-front in my mind as I was shooting the Olympus OM-D E-M1, because I set it up to spot meter from the central spot; however, I’ve been alternating between spot and matrix metering on my Nikon D800E for a long time now, as the shot demands.
The basic ‘rule’ I’m going to try to convey here isn’t really anything unexpected: use the metering mode that works for the shot you are trying to achieve.
But which one to use, when, and why?
Spot metering essentially tells the camera to meter – measure the light present and convey to you (in Manual mode) how under or over exposed the image would be with your current settings, or convey to the camera (in non-Manual modes) what it needs to do to properly expose the image, be it changing the aperture or ISO or shutter speed or a combination thereof – based on that spot in the frame. For the D800E, spot metering tells the camera to measure the light at the AutoFocus selection point you currently have selected. There is a small region around that point that the camera evaluates.
Matrix metering is technically more advanced and computationally more demanding for the camera. In this mode you are basically telling the camera to average out the exposure for the entirety of the frame – the camera tries to give you the settings or exposure value that would best get most of the scene exposed approximately correctly. The camera actually measures thousands of individual points in the frame and compares that measurement to a library of similar exposures in its internal database, and then ‘guesses’ at the right settings needed to properly expose the image.
As an example, here's a shot I took first with Spot metering and then, immediately, switched to Matrix metering and took it again, with all the same settings and minimal processing.
Spot (with the AF point on the place in the clouds where the ray of light is emerging):
Ming Thein has a fantastic and more detailed write-up on these modes here.
Which one to use? Well, here’s what I’ve found:
For landscapes, when I trust the camera (I trust the D800E and the OM-D EM-1 as well as the Sony RX1-R), matrix mode tends to work well. It also works well when I’m not trying to abstract away information via exposure for architecture or plants – in other words, when I’m either going for a documentary approach or I’m deriving my creativity in the image from framing and composition alone, and I want as much of the image to be properly exposed as possible.
For portraits and when I want more careful control over the exposure, I use spot. For example, when the sun is shining through a hole the dappled forest canopy, directly onto a flower, and I deliberately want to expose just that flower and let the shadows around it go deep and dark, spot metering on the brightest part of the flower is perfect.
I’ve found I like the control of spot metering, especially when I have time to think and evaluate the shot. I enjoy high contrast subjects, and spot metering can really allow you to achieve that high-contrast look in-camera (without resorting to a ton of post processing). Done correctly, spot metering can result in images that really pop out at you, or add a sense of almost cinematic drama.
Matrix, on the other hand, is great for when you want an even exposure and when you need to work quickly. You probably will get more ‘hits’ (correct exposures) using Matrix Metering, but you might find those hits are not as strong or interesting visually as the hits you get when you use Spot Metering.
As with many things photography, there’s a large room for personal and artistic preference to the metering modes you choose to use. And, indeed, matrix and spot are not the only types of metering modes out there – the D800E, for example, also has the Centerweight metering mode, although I’ve found I rarely use it (in preference to either matrix or spot).
The best thing to do? Experiment. Go out and shoot the same subject multiple times from different angles with the various metering modes and review how each one behaves. See what they can do for you. Try it at magic hour with a willing or non-living (stationary) subject. Go crazy. Break the rules and see what kind of wild, inventive things you can get up to. It’s amazing what you can do when you get the camera off automatic.