Short answer: use the light meter to get close, then use the histogram to confirm. On a mirrorless camera like the Nikon Z9, you can do both before you even press the shutter. Every photographer has stood in front of a tricky scene, a bright sky, a dark stage, a white wall, and wondered whether the exposure is right.

Your camera gives you two tools to answer that: the light meter and the histogram. People often treat them as the same thing, but they do very different jobs. How you use them also depends on your camera. A DSLR and a mirrorless camera are both digital, but they show you light completely differently.

In this post, I'll explain what each tool really tells you and how moving from a DSLR to a mirrorless body like the Z9 changes how I expose.

The light meter: a prediction.

The light meter measures the scene before you take the picture and suggests settings to expose it correctly. The catch is what "correctly" means to a meter: it assumes everything averages out to a mid-tone, often called 18% grey. That works well for evenly lit, everyday scenes. It fails when the scene is mostly very bright or very dark: snow, white walls, or bright skies make the meter think there's too much light, so it underexposes and turns white into grey. Dark stages, black clothing or night streets make it think there's too little, so it overexposes and washes the blacks out.

Metering modes help. Matrix metering reads the whole frame, centre-weighted favours the middle, and spot metering reads a tiny area. The Z9 also has highlight-weighted metering, which sets exposure to protect the brightest parts of the frame. It's excellent for stage lighting, sunlit buildings and white subjects. But however clever the meter is, it's still a guess made before the shot.

It can't tell you whether anything has actually blown out.

The histogram: the evidence.

The histogram graphs the tones in your picture. Shadows sit on the left, highlights on the right, and the height shows how much of the image falls at each brightness. Unlike the meter, it doesn't care whether your subject is meant to be bright or dark. It simply shows what you've got, bunched against the right edge: highlights are clipping, and that detail is gone. If it's bunched against the left edge, shadows are crushed to pure black. A spike at either edge with a gap beside it: a strong sign of clipping worth checking.

It's also far more reliable than judging brightness on the back screen, which changes with screen settings and the light around you; use the RGB view.

Many cameras show a single brightness histogram by default. If you can, switch to the RGB view. A single colour channel, often red in flowers and sunsets or blue in stage lighting, can clip while the overall brightness looks fine.

A word on raw files.

The camera builds its histogram from a JPEG preview, not from the raw data. That preview applies your Picture Control, so the histogram is usually a little pessimistic. A raw file often holds some extra highlight detail beyond the right edge, which is why your camera and Lightroom can show different histograms for the same shot.DSLR vs mirrorless: when you see the evidence, the biggest difference is timing.

With a DSLR, you check the histogram after the shot; with a mirrorless camera like the Z9, you can see it live, before you press the shutter.

A DSLR uses a mirror to bounce light up into an optical viewfinder. You see the real scene through glass, which is lovely, but it shows you nothing about exposure. The meter's reading is all you have until you take the picture, look at the back screen and check the histogram. Then you adjust and shoot again. A mirrorless camera has no mirror. The sensor is always live, and the electronic viewfinder shows what the sensor sees, with exposure information overlaid.

Mirrorless (Nikon Z9) viewfinder: optical- the real scene through glass; electronic- a live feed from the sensor; histogram only after the shot; on the back screen; live in the viewfinder and on the back screen. Exposure preview: the view stays the same brightness; the view gets brighter or darker as you change settings. Workflow: meter, shoot, check, adjust, reshoot, meter, watch the histogram and adjust.

The main risk is missing a fleeting moment while you check, trusting viewfinder brightness instead of the histogram for street and event photography; that live histogram is a big deal. You rarely get a second chance, so getting the exposure right the first time matters. On the Z9, use both: the meter gets you into the right area, and the live histogram fine-tunes it.

Here's how I set up and use the Z9, but this will also work for most Nikon cameras.

Set up once. Picture Control: Flat, with contrast turned down. The histogram is built from this look, so a flatter Picture Control gives a histogram closer to the raw file.

Your raw files aren't affected. Apply settings to live view: On (in the Custom Settings menu). Without it, the viewfinder stays bright no matter how you expose, and you can't trust the preview. Live histogram in the viewfinder. Add it to one of your viewfinder display modes so it's always a button press away.

RGB histogram in playback.

Turn it on in Playback display options so you can check each colour channel after the shot. Turn Active D-Lighting off so it doesn't change how tones render in the preview. Every shot, meter the scene. Use matrix for general scenes, or highlight-weighted when bright areas matter most. Glance at the live histogram in the viewfinder. Use exposure compensation to move the graph until the important highlights sit just short of the right edge.

When the light is tricky, take the picture and check the RGB histogram in playback; learn your camera's headroom. Shoot a bright scene at increasing exposures, then open the raw files in Lightroom. Note the point where the camera warns of clipping, but Lightroom can still recover the detail. That tells you how much you can trust "touching the right edge" on your own camera. So which matters more? For judging the exposure you've actually captured, the histogram wins. The meter predicts; the histogram proves. But they work best as a team, and on a mirrorless camera they work together in real time.

Neither tool knows what matters in your picture, though sometimes I'll happily let a sky blow out behind a silhouette, or let shadows fall to black on a moody street at night.

The histogram doesn't stop me from doing that. It tells me exactly what I'm giving up, so the choice is mine, not an accident. That's the real value of these tools: not perfect exposures by the numbers, but knowing your exposure is a decision, not a guess.