What Is An F-Stop?
F-stops are a measure of how much light enters your camera. F-stops are also called “stops” or “focal ratios” and are represented by a number followed by an “f”. For example, f/2.8 is an f-stop. Knowing how to use and understand f-stops is an important part of photography and understanding exposure.
An f-stop is a number that represents how wide your lens is open when you take a photo. The lower the f-stop number, the wider your lens is open, and the more light that enters your camera. Conversely, the higher the f-stop number, the narrower your lens is open, and the less light that enters your camera.
How To Use F-Stops
The most common way to use f-stops is to adjust how much light enters your camera. By changing the f-stop, you can make your photos darker or brighter. You can also use f-stops to adjust your depth of field. A lower f-stop number will give you a shallow depth of field, and a higher f-stop number will give you a deeper depth of field.
F-stops are an important part of photography, and understanding how to use them will help you take better photos. By understanding related topics, such as shutter speed, aperture, ISO, exposure triangle, and metering modes, you will be able to get the most out of your f-stop settings.
This video explains f-stops quite nicely:
video by PhotoProTips
This video goes beyond just f-stops:
video by PhotoProTips
Related Topics In Photography
When learning about f-stops, it is important to understand related topics in photography, such as:
- Shutter Speed – This is how long your camera shutter stays open when you take a photo.
- Aperture – This is the size of the hole in your lens that lets light into your camera.
- ISO – This is the sensitivity of your camera’s sensor to light.
- Exposure Triangle – This is the relationship between the three elements of exposure: shutter speed, aperture, and ISO.
- Metering Modes – This is the way your camera calculates the correct exposure for a photo.
Related Pages:
The F-Stop Scale Explained
The standard f-stop scale follows a specific sequence: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Each step in this sequence is called a “full stop.” Moving from one full stop to the next either doubles or halves the amount of light reaching your sensor. For example, changing from f/4 to f/2.8 doubles the light, while changing from f/4 to f/5.6 cuts the light in half.
Modern cameras also offer third-stop increments between these values, such as f/3.2 and f/3.5 between f/2.8 and f/4. These finer adjustments give you more precise control over exposure without making drastic changes.
The f-number itself is a ratio of the lens focal length to the diameter of the aperture opening. An f/2 setting on a 50mm lens means the aperture opening is 25mm wide. This is why the numbers seem “backwards” to beginners. A smaller f-number means a larger opening, letting in more light and producing a shallower depth of field in your images.
How F-Stops Affect Your Photos
Every f-stop choice creates a tradeoff between light and sharpness depth. Wide apertures like f/1.8 or f/2.8 let in lots of light and create a soft, blurred background. This makes them ideal for portraits and low-light situations. Narrow apertures like f/11 or f/16 let in less light but keep more of the scene sharp from front to back. Landscape photographers often shoot between f/8 and f/11 for this reason.
Most lenses have a “sweet spot” where they produce the sharpest images. This is typically two to three stops down from the maximum aperture. For a 50mm f/1.8 lens, the sharpest results usually come around f/5.6 to f/8. Shooting at the very widest or narrowest apertures can reduce overall sharpness due to optical aberrations or diffraction.
Using Aperture Priority Mode lets you set the f-stop while the camera automatically adjusts bokeh for correct exposure. This is a practical way to learn how different f-stops affect your images without worrying about underexposure or overexposure.
F-Stops in Different Photography Styles
Portrait photographers typically use wide apertures between f/1.4 and f/2.8 to separate the subject from the background with creamy portrait lighting. The shallow depth of field draws attention directly to the person.
Landscape photographers prefer f/8 to f/16 to keep everything sharp from foreground to horizon. Pair this with a sturdy tripod since narrow apertures require slower shutter speeds or higher ISO values. Shooting during shutter speed with a narrow aperture creates stunning detail throughout the frame.
Street photographers often use f/8 as a default because it provides a deep zone of acceptable focus, making it easier to capture quick, unplanned moments without needing to nail precise focus every time.
Common Mistakes
- Shooting wide open at f/1.4 for every photo. While the background blur looks appealing, the extremely thin focus plane means important details (like a second eye in a portrait) can end up soft.
- Using the narrowest aperture (f/22) thinking it gives the sharpest result. Diffraction at very small apertures actually softens the image. Stick to f/8 through f/16 for maximum sharpness.
- Ignoring the relationship between f-stop and ISO. Choosing a narrow aperture in dim light forces the camera to raise ISO, which adds noise to your photos.
- Forgetting that different lenses have different maximum apertures. A kit lens at 55mm might only open to f/5.6, limiting your background blur options.
Try This
- Set your camera to Aperture Priority mode. Photograph the same subject at f/2.8, f/5.6, f/8, and f/16. Compare the background blur and overall sharpness in each shot.
- Find a scene with objects at different distances. Shoot at your widest aperture and then at f/11. Notice how the narrow aperture brings more elements into focus.
- Test your lens sweet spot: shoot a detailed subject (like a brick wall or bookshelf) at every f-stop from wide open to f/16. Zoom to 100% on your computer and find which f-stop is sharpest.
- Practice shooting in low light at a wide aperture, then review your composition techniques to check if you are blowing out highlights.
Frequently Asked Questions
What is the best f-stop for beginners?
Start with f/5.6 to f/8. This range offers a good balance of depth of field and sharpness on most lenses. It is also forgiving if your focus is slightly off, since more of the scene stays sharp compared to shooting wide open.
Does a lower f-stop always mean better photos?
No. A lower f-stop gives you more light and background blur, but it also narrows your depth of field. This can be a disadvantage when you need multiple subjects in focus, such as group photos or landscapes. The best f-stop depends entirely on your creative goal.
Why are fast lenses (low f-stop) more expensive?
Lenses with wide maximum apertures like f/1.4 require larger, more precisely ground glass elements. The engineering needed to maintain sharpness across a wide opening significantly increases manufacturing cost. For many photographers, an f/1.8 lens offers nearly the same performance at a fraction of the price.
Can I change the f-stop on my phone camera?
Most phone cameras have a fixed physical aperture. However, many phones simulate aperture effects in their portrait mode using software-based depth estimation. The “f-stop” setting in some phone camera apps only adjusts the strength of this simulated blur, not the actual lens opening.