A practical introduction to aperture, depth of field, macro work, shutter speed and ISO -- the fundamentals behind every photograph on this site.
Aperture is the opening inside your lens that controls how much light reaches the sensor. It's measured in f-stops (f/1.4, f/2.8, f/8, f/16...) -- and confusingly, a smaller f-number means a larger opening. f/1.4 lets in far more light than f/16.
Beyond exposure, aperture is the main tool for controlling depth of field -- how much of the image is in sharp focus versus soft and blurred.
Wide apertures (f/1.4 -- f/2.8) are ideal for portraits, isolating a subject with a blurred background ("bokeh"). Narrow apertures (f/8 -- f/16) suit landscapes, keeping foreground and background both sharp.
Depth of field (DoF) is the zone of a photo that appears acceptably sharp. Three factors control it:
| Factor | Effect on DoF |
|---|---|
| Wider aperture (smaller f-number) | Shallower depth of field |
| Longer focal length (more zoom) | Shallower depth of field |
| Closer focusing distance | Shallower depth of field |
This is why a telephoto portrait lens at f/1.8 blurs the background dramatically, while a wide-angle landscape lens at f/11 keeps a mountain range and foreground flowers both in focus.
Macro photography is extreme close-up work -- photographing small subjects (insects, flowers, water droplets, textures) at high magnification, often at or near life-size (1:1) reproduction on the sensor.
Because you're shooting so close, depth of field becomes razor-thin -- sometimes just a few millimetres. This changes the usual rules:
Narrow aperture (f/11 -- f/16): needed just to keep a whole subject in focus at close range.
Manual or precise focus: autofocus often hunts at 1:1 magnification -- many macro shooters focus manually or focus-stack.
A tripod or stabilisation: at high magnification, even breathing motion causes blur.
Extra light: narrow apertures and close distances mean less light reaches the sensor -- a diffused flash or ring light helps.
Focus stacking -- combining multiple shots focused at slightly different distances -- is a common technique to overcome the shallow depth of field inherent to macro work.
Shutter speed controls how long the sensor is exposed to light, measured in fractions of a second (1/1000s, 1/125s) or full seconds for long exposures. It affects both exposure and how motion is rendered.
| Speed | Typical use |
|---|---|
| 1/1000s or faster | Freezing fast action -- sports, birds in flight |
| 1/125s -- 1/250s | General handheld shooting, street photography |
| 1/30s -- 1/60s | Slower handheld work, subtle motion blur |
| 1s or longer | Long exposures -- flowing water, light trails, night skies |
Fast-moving subjects -- birds taking flight, a runner mid-stride -- rely on a fast shutter speed to freeze motion sharply against a still background.
Aperture, shutter speed and ISO (sensor sensitivity) together form the exposure triangle. Adjusting one affects how you need to balance the other two to keep the same overall exposure.
Controls light and depth of field. Wider = more light, shallower focus.
Controls light and motion. Faster = less light, frozen motion.
Controls sensor sensitivity. Higher = brighter but noisier images.
Keep ISO as low as the light allows -- it's the setting most likely to degrade image quality. Adjust aperture for the depth of field you want first, then use shutter speed and ISO together to reach a correct exposure.
Every technique above shapes the photographs in my portfolio.
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