How do I tell if I'm under- or overexposed?

Look at the histogram: a peak slammed against the right edge signals blown highlights (overexposure); a peak against the left edge means crushed shadows (underexposure). The ideal is a distribution spread across the full width, with no pile-up at the edges. Most camera bodies also offer *blinkies* on blown zones in playback — very useful in the field.

Better to slightly underexpose or overexpose?

In digital, we long recommended slightly overexposing to preserve the signal-to-noise ratio (the *ETTR* technique, expose to the right). But on modern sensors, it's better to avoid clipping on the highlight side: a blown detail is gone for good, while a slightly underexposed shadow recovers cleanly in post.

How do I handle exposure for Reels or vertical video?

In video, shutter speed is constrained by frame rate (the 180° rule: 1/50s at 25 fps). So you work first with ISO and aperture, and use ND filters outdoors if you want to keep shallow depth of field. Lock exposure (AE-Lock) to avoid abrupt shifts during motion.

Technical Analysis

Exposure

Exposure is the amount of light that reaches the sensor — no more, no less.

Photo : Joshua Earle / Unsplash

Definition

What is exposure?

Exposure is the total amount of light that reaches the sensor during a shot. It's controlled through three levers: aperture, shutter speed and ISO sensitivity. We measure it in stops (or EV, exposure values): one stop equals a doubling — or halving — of the light captured. Correct exposure avoids two pitfalls: blown highlights (white zones with no detail) and crushed shadows (black zones with no information). That balance is what we call the exposure triangle.

Example

In practice

Picture an outdoor portrait, late afternoon, soft but contrasty light. You switch to A/Av (aperture priority) at f/2.8 to isolate your subject, then engage spot metering on the face: that's what needs to be correctly exposed, not the sky behind. If the image looks too dark, dial in exposure compensation at +0.7 EV. In S/Tv (shutter priority), you set the shutter speed to freeze motion and let the body pick the aperture. In M (manual), you pilot all three parameters yourself. Everything rests on the exposure triangle.

Common mistakes

What we see too often

Full auto in a high-contrast scene. Backlight, neon, a window behind the subject: the meter averages everything and serves up a blown or crushed face. Take back control with spot metering or exposure compensation.

Ignoring the histogram. The rear screen lies, especially in bright sun. If you don't check the histogram at capture, you'll discover the blown zones in post — when it's already too late to recover detail.

How Focalis evaluates

How Focalis evaluates exposure

Focalis-X reads the EXIF data (aperture, shutter speed, ISO, compensation), analyzes the image's histogram and automatically detects clipping in both highlights and shadows. You get an exposure score, problem zones mapped, and concrete correction paths. Analyze a photo →

FAQ

Frequently asked questions

How do I tell if I'm under- or overexposed?
Look at the histogram: a peak slammed against the right edge signals blown highlights (overexposure); a peak against the left edge means crushed shadows (underexposure). The ideal is a distribution spread across the full width, with no pile-up at the edges. Most camera bodies also offer blinkies on blown zones in playback — very useful in the field.
Better to slightly underexpose or overexpose?
In digital, we long recommended slightly overexposing to preserve the signal-to-noise ratio (the ETTR technique, expose to the right). But on modern sensors, it's better to avoid clipping on the highlight side: a blown detail is gone for good, while a slightly underexposed shadow recovers cleanly in post.
How do I handle exposure for Reels or vertical video?
In video, shutter speed is constrained by frame rate (the 180° rule: 1/50s at 25 fps). So you work first with ISO and aperture, and use ND filters outdoors if you want to keep shallow depth of field. Lock exposure (AE-Lock) to avoid abrupt shifts during motion.