What is Exposure?

Exposure determines how bright or dark an image appears, but it’s subjective and only considered correct when it accurately represents the intended brightness of the subject.

Exposure is controlled by the delicate balance between the amount of light allowed to reach the sensor through lens and by the duration of time the curtain (shutter) stay open for.

PhotoClassOne Left: Overexposed building, appearing excessively bright. Center: Correctly exposed building.
Right: Underexposed building, resulting in a dark scene.

The Exposure Triangle

Here’s where the Exposure Triangle comes in. It’s like a three-legged stool, and each leg plays a crucial role in controlling the amount of light reaching the sensor:
  1. Aperture
    Think of this as the size of the hole in the lens that lets light in. Imagine a doorway: a wider opening (low f-number) allows more light, while a narrower opening (high f-number) lets in less. This also affects the depth of field, which is the area that appears sharp in your photo. A wider aperture creates a shallow depth of field, blurring the background and making your subject pop. A narrower aperture creates a deeper depth of field, keeping everything in focus, front to back.

2. Shutter Speed
This is like the duration for which the “doorway” stays open, letting light flood in. A slow shutter speed lets in more light but may cause motion blur if your subject or the camera moves. A fast shutter speed freezes the action, perfect for capturing that epic jump shot or a playful water splash.

PhotoClassOne

Shutter speed of 1/2000

Shutter speed of 1/40

Shutter speed of 1/2

3. ISO Film Speed
Back in the day, we used film that had a certain sensitivity to light, measured by an ISO number. The higher the ISO, the more sensitive it was (like having super night vision!). Today, even though we use digital sensors, ISO still works the same way. But here’s the catch: while higher ISO helps in low-light situations, it can also introduce digital noise (graininess) into your photos.

Think of ISO as a volume knob for your camera’s sensitivity to light. Turning it up boosts sensitivity, useful in dim conditions. But just as blasting volume can distort sound, excessive ISO can introduce graininess. So, it’s crucial to find the right level for clear, well-exposed photos.

The Balancing Act

Let’s say you’re shooting a landscape at sunset. Your camera suggests a shutter speed of 1/120 second at ISO 800, but you want a longer exposure to capture flowing water. If you lower the shutter speed by half to 1/60, the image will become too bright. To compensate, halve the ISO value to 400 or close the aperture, or use a combination of both adjustments.

The key is to balance these three elements to achieve the desired exposure and creative effect. Experiment! Try different combinations of aperture, shutter speed, and ISO to see how they affect your photos. Remember, “just right” isn’t always the best. Sometimes, underexposing or overexposing can create cool effects, like a dramatic silhouette.

“Correct” isn’t always Right

Achieving the perfect exposure isn’t always the goal. Sometimes, underexposing or overexposing intentionally can create artistic effects. Silhouette photography, for instance, often involves deliberate underexposure for striking results.

So, the next time you pick up your camera, remember the Exposure Triangle. With a little practice, you’ll be controlling light like a pro, capturing stunning photos that go beyond “auto” mode!