The F-number, also known as aperture, plays a major role in how a photograph looks and feels.
It affects image brightness, background blur, and how much of the scene appears sharp.
By understanding how F-numbers work, you gain direct control over light, depth of field, and creative intent.
This applies across everyday photography in Singapore, from portraits and family moments to cityscapes and night scenes.
Different shooting situations call for different F-number choices.
Portraits, landscapes, night photography, sports, and astrophotography all benefit from specific aperture settings.
In this article, we explain what the F-number is, how it works, and why it matters.
We also show how aperture interacts with shutter speed and ISO, using practical examples you can apply straight away.
The goal is simple.
Help you make confident aperture choices so your photos look intentional and well balanced.
What is an F-number (aperture)?
In photography, the F-number is a core setting used to control how much light enters the camera.
It also influences background blur and how much of the scene appears sharp.
The aperture sits inside the lens and opens or closes to regulate light.
The size of this opening is expressed as the F-number, also called the aperture value.
How the F-number is calculated
The F-number is calculated using a simple formula.
F-number equals the focal length of the lens divided by the diameter of the aperture opening.
F = f ÷ D
A smaller F-number means a larger opening.
More light reaches the camera sensor.
A larger F-number means a smaller opening.
Less light enters the camera.
This explains why F2 lets in more light than F8.
It also explains why F2 produces stronger background blur.
Aperture shape and bokeh
Aperture blades form the shape of the opening inside the lens.
This shape affects how out-of-focus highlights appear in your image.
Lenses with more rounded aperture blades produce smoother, more circular bokeh.
This is especially noticeable with city lights, street lamps, and night scenes.
TAMRON lenses use multi-blade diaphragm designs to maintain smooth bokeh.
This stays consistent even when you stop down slightly.
Why the F-number matters
The F-number directly affects exposure, image quality, and creative control.
It works together with shutter speed and ISO as the three exposure controls.
In low-light conditions such as evening street scenes or indoor events, a smaller F-number helps gather more light.
This lets you keep shutter speeds faster or ISO values lower.
In bright outdoor conditions, a larger F-number helps control exposure.
It also increases depth of field, which keeps more of the scene in focus.
Choosing the right F-number helps you balance clarity, motion control, and noise.
This balance becomes easier with practice.
Maximum aperture and wide-open shooting
The widest aperture a lens can achieve is called its maximum aperture.
Photographers often call this shooting wide open.
A lens with a wide maximum aperture performs better in low light.
It also produces stronger background separation.
This is useful for portraits, indoor photography, and fast-moving subjects.
It gives you flexibility when light levels drop.
How different F-numbers change the look of a photo
Changing the F-number alters depth of field.
Depth of field is how much of the image appears sharp from front to back.
A smaller F-number creates shallow depth of field.
Only a narrow area stays in focus, while the background blurs.
A larger F-number creates deeper depth of field.
More of the scene appears sharp, from foreground to background.
This is why portraits often use small F-numbers.
Landscapes usually benefit from larger F-numbers.
F-number, shutter speed, and ISO
These three settings work together to control exposure.
Changing one affects the others.
When you use a small F-number, more light enters the camera.
You can use a faster shutter speed or a lower ISO.
This reduces motion blur and image noise.
It also helps isolate your subject from the background.
When you use a large F-number, less light reaches the sensor.
You may need a slower shutter speed, a higher ISO, or both.
Slower shutter speeds increase the risk of camera shake.
A tripod helps in these situations.
Higher ISO increases image noise.
Find a balance that suits your subject and shooting conditions.
Using Aperture Priority mode
Aperture Priority mode lets you select the F-number.
The camera sets the shutter speed automatically.
This mode works well when depth of field matters more than motion.
You control the look, and the camera handles exposure timing.
A smaller F-number results in faster shutter speeds.
A larger F-number results in slower shutter speeds.
Watch your shutter speed to avoid camera shake.
Adjust ISO or aperture if needed.
Constant aperture zoom lenses
Many zoom lenses change maximum aperture as you zoom.
As you zoom in, the widest available F-number often becomes larger.
Some zoom lenses maintain the same maximum aperture throughout the zoom range.
These are known as constant aperture zoom lenses.
The main benefit is simpler exposure control when zooming in or out.
Your shutter speed and ISO stay more consistent because light intake stays stable.
Choosing an F-number for different scenes
There is no single F-number for every situation.
Your subject, environment, and intention should guide your choice.
Below are practical examples with sample settings.
Use them as starting points, then adjust based on light and movement.
Best aperture for portraits
Portrait photography often aims to separate the subject from the background.
Shallow depth of field helps achieve this effect.
F2.8 is commonly used on standard zoom lenses.
F1.4 is common on prime lenses.
Example
Lens: 35-150mm F/2-2.8 Di III VXD (Model A058)
Focal length: 35mm
Aperture: F2
Shutter speed: 1/800 sec
ISO: 200
Camera: Sony α7R IV
Using an aperture close to wide open increases background blur and keeps attention on the subject.
A wider maximum aperture also helps keep shutter speed higher or ISO lower in indoor and evening conditions.
Best aperture for landscape photography
Landscape photography prioritises detail across a wide area.
To increase depth of field, stop down the aperture with a larger F-number.
F8 to F11 is a common range for landscapes.
This helps keep the scene sharp from foreground to background.
Avoid stopping down more than needed.
At around F16 and beyond, diffraction can reduce overall sharpness.
Example
Lens: 50-400mm F/4.5-6.3 Di III VC VXD (Model A067)
Focal length: 50mm
Aperture: F8
Shutter speed: 1/500 sec
ISO: 100
Camera: Sony α7R IV
Best aperture for night views
For night cityscapes, you often want detail across the frame, similar to landscape photography.
F8 to F11 is a common range for sharpness and clean light trails.
Because less light reaches the sensor at these settings, you will rely on slower shutter speeds or higher ISO.
Use a tripod to reduce camera shake, then keep ISO as low as the scene allows.
Example
Lens: 17-70mm F/2.8 Di III-A VC RXD (Model B070)
Focal length: 70mm
Aperture: F8
Shutter speed: 15 sec
ISO: 160
Camera: FUJIFILM X-T4
Best aperture for astrophotography
To capture stars and the Milky Way, you need to gather as much light as possible.
F2 to F2.8 is a common range, close to wide open.
Long exposures help, but earth rotation can cause stars to stretch into trails.
Start with shorter exposures and adjust based on focal length and your result.
Example
Lens: 11-20mm F/2.8 Di III-A RXD (Model B060)
Focal length: 20mm
Aperture: F2.8
Shutter speed: 10 sec
ISO: 1000
Best aperture for sports events
Sports and action scenes need fast shutter speeds to freeze motion.
A moderately wide aperture helps you keep shutter speed high without pushing ISO too far.
F4 to F8 is a useful range when you want more depth of field, so subjects stay sharp as they move.
Increase ISO when needed to maintain a shutter speed suitable for the action.
Example
Lens: 70-300mm F/4.5-6.3 Di III RXD (Model A047)
Focal length: 70mm
Aperture: F4.5
Shutter speed: 1/1250 sec
ISO: 500
Recommended lens featured in this article
If you want a compact full-frame zoom that stays simple for both photo and video, consider the 17-50mm F/4 Di III VXD (Model A068).
A constant F4 maximum aperture keeps exposure changes predictable as you zoom, which helps when light levels change quickly.
Bring it all together
The F-number shapes brightness, background blur, and how much of your scene appears sharp.
Once you understand how aperture works with shutter speed and ISO, you can set exposure with intent instead of guesswork.
Try one location you know well, like Marina Bay, Gardens by the Bay, or your neighbourhood park.
Change only the F-number each time, then watch how the photo changes and how the camera compensates.