What is aperture measured in

What Is Aperture? | Understanding Camera Aperture from Nikon

Beginner

Learn how aperture affects the end-result image.

Glossary

What is aperture in photography?

Aperture refers to the opening of a lens's diaphragm through which light passes. It is calibrated in f/stops and is generally written as numbers such as 1.4, 2, 2.8, 4, 5.6, 8, 11 and 16. Lower f/stops give more exposure because they represent the larger apertures, while the higher f/stops give less exposure because they represent smaller apertures. This may seem a little contradictory at first but will become clearer as you take pictures at varying f/stops. Be sure to check your manual first to learn how to set Aperture Priority for your camera, then try experimenting to get comfortable with changing the aperture and recognizing the effects different apertures will have on the end-result image.

How Aperture Affects Depth of Field

Depth of field is the zone of acceptable sharpness in front of and behind the subject on which the lens is focused. Simply put: how sharp or blurry is the area behind your subject.

The lower the f/stop—the larger the opening in the lens—the less depth of field—the blurrier the background.

The higher the f/stop—the smaller the opening in the lens—the greater the depth of field—the sharper the background.

How Aperture Affects Shutter Speed

Using a low f/stop means more light is entering the lens and therefore the shutter doesn't need to stay open as long to make a correct exposure which translates into a faster shutter speed. Again, the reverse is true: using a high f/stop means that less light is entering the lens and therefore the shutter will need to stay open a little longer which translates into a slower shutter speed.

Where to Find Aperture on a Nikon Lens

All lenses have a maximum aperture, and all NIKKOR lenses list the widest possible aperture on the lens barrel. Some zoom lenses will detail something like f/3. 5-5.6 on the lens barrel or 1:3.5-5.6 (below right). These numbers, the 3.5 and the 5.6, are referring to the maximum aperture or widest opening the lens can achieve for each end of the zoom range. Some higher end lenses can maintain the largest aperture throughout the entire zoom range, so only one number is detailed (below left).

How to Choose Aperture

Now that we know how to control depth of field, what determines the choices we make in selecting the aperture? We use focus and depth of field to direct attention to what is important in the photograph, and we use lack of focus to minimize distractions that cannot be eliminated from the composition. While there are no rules, there are some guidelines for selecting Aperture priority.

Aperture for Portraits

For classic portraiture we separate our subject from the surroundings by using "selective focus." Choosing a large aperture (lower f/stop, like f2.8) creates very shallow depth of field with only the subject, or just a portion of the subject, in focus. This helps direct the viewer's attention to the subject.

Aperture for Landscape Photography

When choosing lenses for landscape photography, we usually want to see as much detail as possible from foreground to background; we want to achieve the maximum depth of field by choosing a small aperture (higher f/stop, like f/8 or f/11).

Aperture for Intermediate Depth of Field

While we can get the maximum or minimum depth of field by working at each end of the aperture range, sometimes we want a more intermediate level of depth of field, limiting focus to a specific range of distances within the overall photograph. One way to do this is to choose a mid-range f/stop, like f/5.6, and shoot a test frame. In image playback, use the magnifying function of the LCD to zoom in and check the depth of field; make adjustments if necessary and reshoot.

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The Basics of Aperture Guide, Pt. 1: How Is Aperture Measured?

Photographers don’t usually get too far into their journeys before stumbling upon the exposure triangle. Each component of the triangle, which includes shutter speed, aperture, and ISO, unlocks new directions in which we can take our pictures. Once we cross the bridge from shooting in automatic mode over to shooting in manual mode, we rarely ever look back. After all, capturing images in manual mode affords us a creative freedom we’d never find if we stayed behind and continued letting the camera make all of our exposure decisions for us. Of the three components that comprise the exposure triangle, we’re going to turn our attention to aperture, the element most responsible for controlling the depth of field in our images. This article will kickstart our basics of aperture guide and answer the questions, how is aperture measured and what is its role in photography?

The Basics of Aperture Guide: How Is Aperture Measured?

What Is Aperture?
Measuring Aperture with F-Stops
Lens Speed
Aperture and Balancing Exposure

What is Aperture?

The simplest explanation for understanding the basics of aperture is this: aperture refers to the opening inside the lens in which light can shine through. Moreover, a set of overlapping metal blades, called a diaphragm, determines the size of the aperture’s opening. Alongside shutter speed, aperture limits the amount of light that can hit the sensor at any given time. Just think of this opening like the valve handle of a water faucet. The wider you open the faucet, the more water pours out. The wider the aperture opening, the more light pours into the sensor.

Most modern lenses allow you to control the size of the aperture opening from the camera itself. Some modern lenses, and the majority of vintage lenses, have an aperture ring on the lens that allows you to control the diaphragm directly on the lens.

How Is Aperture Measured?

Understanding how is aperture measured can be confusing at first. This is because aperture is measured in what is known as f-numbers or f-stops, which is the ratio of the lens’ focal length divided by the effective aperture diameter. In other words, if you take a 200mm lens and divide it by a 50mm aperture diameter opening, you end up with an f-stop of 4, or f/4. Now, for a 100mm lens, you only need an aperture diameter opening of 25mm to get to f/4.

Unlike shutter speed, for instance, which is measured in absolute value of time, an f-stop is relative to the length of the lens and the diameter of the aperture opening itself.

A Pizza Analogy for Understanding F-Stops

The main thing that you have to remember about f-stops is that they represent inverse values. This means that just like a fraction, the larger the number is, the smaller the diameter opening. A way to visualize this is to think of slices of a pizza pie. A quarter (1/4) slice of pie is larger than an eighth (1/8) slice of a pie. So an aperture opening with a lower value like f/4 is a larger than an aperture opening with a higher value like f/8. In other words, a large or open aperture has a low f-stop number, while a small or closed aperture has a high f-stop number.

How Is Aperture Measured? Introducing the Factor of √2

Got that? Ok, because the basics of aperture may get a little more confusing from here. Going back to the slice of pie analogy, we all know that a 1/8 slice of pizza is half as big as a ¼ slice of pizza, and a 1/16 slice is going to be half as big as a 1/8 slice of pizza. With f-stops, the halving/doubling relationship doesn’t quite work in the same way. In order to double or half the amount of light coming in, multiply by a factor of √2 (approximately 1.41).

What Is a Full Stop of Light?

Doubling or halving the light is called one full stop. So, going from f/4, if you want to cut the light coming in by half or go one full stop down, you multiple f/4 by 1.41, which gets you f/5.6. If you cut that light in half again, you get f/8. So unlike the pizza slices where a 1/8 pizza slice is half the size of a ¼ pizza slice, an f/8 aperture lets in a quarter of the light compared to an f/4 aperture.

Now, when you want to double the amount of light coming in, or go one full stop up, you divide by 1. 41. So starting back at f/4, to go one full stop up, you divide by 1.41 to get f/2.8.

So here is a diagram that shows you the list of full f-stops from f/1 to f/22:

How Is Aperture Measured? Getting to Know Other Stops of Light

In between the full f-stops are 1/2 stops and 1/3 stops. These fractional f-stops gives you more control over how much light you allow in. Here is the same diagram with the 1/2 stops and 1/3 stops added.

The Basics of Aperture: Lens Speed

You may have noticed that lenses are typically labeled with an f-stop number. This is what is known as the lens speed or the maximum aperture available for that lens.

Fixed Aperture Prime Lens

Because they can gather light quickly, prime lenses with large apertures (f/1.8 or wider) are considered “fast lenses.” On the other hand, a “slow lens” might have a maximum aperture of f/4. Some lenses, like the Voigtlander Nokton 25mm or the Leica Noctilux 50mm have a maximum aperture of f/0. 95! Now that is blazing fast! Of course, you pay the high price for these lenses, with the Leica Noctilux retailing for just under $13,000.

Fixed and Variable Zoom Lens Aperture

Zoom lenses come in two varieties, variable maximum aperture and constant (or “fixed”) maximum aperture. Typically, it is the high-end zoom lenses like the Canon EF 24-70mm f/2.8L USM Standard Zoom Lens that have a constant max aperture, while the cheaper zoom lenses like the kit lens that comes with a DSLR like Canon EF-S 18-55mm f/3.5-5.6 IS II SLR Lens have a variable max aperture. The reason that the higher end lens with the constant max aperture is far more expensive is because the lens manufacturer has to figure out how to maintain the same max aperture without actually having to increase the diaphragm diameter.

The Basics of Aperture and Balancing Exposure

So what is the point of all these f-stops in regards to answering the question of how is aperture measured? One of the reasons that you want adjustable aperture is to control exposure. When one or more factors of the exposure triangle increases or decreases one way, the other factors must swing the other way in order to maintain the same exposure.

Therefore, if we slow down the shutter speed by one stop, we’re doubling the amount of light hitting the sensor. In order to have the same exposure as before, we have to close down the aperture by one stop. Conversely, if we speed up the shutter speed by one stop, then we must also open up the aperture by one stop. The same principle applies with ISO.

Using Aperture to Correct Under and Overexposure

You can use aperture to correct for under and overexposure, as well. If your image is too dark, try opening up your aperture to let more light in. If your image is too bright, stop down the aperture to limit the amount of light hitting the sensor.

For an easy way to remember how to balance exposure, remember the water faucet analogy. If you have a lot of water pouring out (large aperture), you only need a short amount of time to fill a cup (short shutter speed). If you allow less water to pour out (small aperture), it will take you longer to fill the same cup (long shutter speed).

Conclusion

Let’s recap the basics of aperture. Aperture refers to the lens opening that works with shutter speed to control how much light can hit the sensor. An adjustable set of overlapping metal blades, called the diaphragm, determines the size of this opening. The bigger the opening, the more light comes through at any given time. We use “f-stops” to measure aperture, which notes the ratio between the focal length of the lens and the actual diameter diaphragm opening. To double or half the amount of light coming in, we multiply or divide by a factor of √2. Finally, we rate lenses based on their maximum aperture or lens speed. Fast lenses can open up to f/1.4 or faster to let a lot more light in.

In an upcoming article, we’ll go more “in-depth” at how aperture influences depth of field and focus. Until next time!

What is aperture and how does it affect the quality of your photos?

Surely, many of you use your smartphone as the main camera. Even those who have a cool or not-so-great DSLR will not argue with how convenient it is to have a good camera that fits in your pocket. In fact, the camera quality of a flagship smartphone is now more than enough to capture most everyday moments. In order to maintain interest in their products, manufacturers are constantly trying to bring something new to smartphone cameras that already know how to photograph well. In addition to the trend to increase the number of cameras in devices, the last few generations of smartphones also boast ever wider apertures. But what is this aperture?

Smartphones with apertures of ƒ/1.8 or higher are no longer rare these days, which used to be a big achievement even for professional grade lenses. Devices like the iPhone XS Max, Pixel 3 XL, and Huawei Mate 20 Pro have ƒ/1.8 apertures. However, some manufacturers show us a completely different level. The Samsung Galaxy S10 and LG V40 have an aperture value of ƒ/1.5.

All these numbers are of course important, but does this aperture value really make photos better? This is the question we will try to answer in this article.

Contents

1 What is aperture? It's all about the amount of light
2 What is "ƒ" (relative lens aperture)
3 Lens quality
4 To sum it all up

What is aperture? It's all about the amount of light

Generally speaking, a photograph is only light received and processed in a certain way. Therefore, a good parameter for determining the quality of a particular camera is to determine its ability to process light. A quality sensor paired with a cool lens is a popular combination for SLR cameras, and the same applies to smartphones, albeit with some limitations.

The compact size of a smartphone means that the lenses and sensors are smaller, so less light will reach them, and this directly affects the final quality of photos. We've seen smartphone manufacturers use large sensor pixel sizes from 1.2 to 1.55 µm to combat this limitation with great results, but another strict coin is the amount of light that can enter through a lens to achieve these pixels. This is where aperture comes into play.

What is "ƒ" (relative lens aperture)

So what is aperture? Aperture is the size of the opening through which light can enter the camera. Aperture is measured in so-called “ƒ”, which is the ratio of the diameter of the entrance pupil of the lens to its rear focal length. So the smaller the aperture, the wider the aperture and therefore more light can reach the sensor, resulting in less noise in the photo.

A smaller aperture size also has the advantage when it comes to reducing the exposure time required to capture just the right amount of light, reducing blur when shooting in motion or with shaky hands. In combination with good stabilization, the smaller aperture size can give the photographer a clear shot even in not the best conditions.

When talking about camera lenses, photography enthusiasts often associate a wider aperture with a shallower depth of field, which produces that same background blur effect called bokeh. However, a smartphone camera with an ƒ/2.2 aperture actually only provides a depth of field equivalent to an ƒ/13 or ƒ/14 aperture on a full-frame camera, resulting in a bit of blur, so modern smartphones that boast great bokeh actually achieve this effect. with the help of software.

Although a wide aperture is not a guarantee of a high quality camera, a smaller aperture allows more light to enter the sensor, resulting in faster shutter speeds and less blur and noise in the photo. This value should always be considered in conjunction with the pixel size, as larger pixels do not necessarily require a wider aperture to capture enough light. However, small pixels and a small aperture are a sure sign that low light conditions will be a problem.

Lens quality

An equally important but often overlooked component of smartphone cameras is the lens, and like everything else, they also vary considerably in quality. After all, a dirty lens makes for poor pictures, and it follows that a lens glass with poor clarity or transparency will reduce the amount of light reaching the sensor and therefore reduce image quality.

Wide aperture smartphones like the new Galaxy S10 require special attention to lens design to avoid lens distortion and flare, a common problem on mobile devices. Distortion or aberration distortion is a whole range of problems that arise when a beam of light deviates from the direction in which it would have to go in an ideal optical system. Smartphones with a wide aperture are, by definition, less focused on a certain part of the scene than smartphones with a more closed aperture, and therefore more prone to problems.

Aberration distortion has many effects. These include spherical aberration (reduced clarity and sharpness), coma (blurring or distortion), field curvature (loss of focus at the edges), distortion (distortion) (convexity or concavity of the image), and chromatic aberration (out of focus colors and split white light) and others.

One of the most important parameters is the quality of the lens, and it is more difficult to judge it from the specifications, since many phone manufacturers do not even mention it. This factor complicates conversations about aperture and pixel sizes, since cheaper lenses can bring all these parameters to naught. Fortunately, there are several well-known optical manufacturers in the smartphone market now, including Zeiss and Leica.

Summarizing all of the above

Now you know what an aperture is. But as you probably already understood, the aperture is not all that makes a quality camera. When choosing a smartphone, focusing on its photo capabilities, dwelling on the aperture value alone will be wrong, since apart from other parameters this number is almost useless. However, a smaller aperture value offers a number of advantages, including the ability to take a good photo in low light conditions.

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Aperture (optics) | it's... What is Aperture (optics)?

This term has other meanings, see Aperture.

Large (1) and small (2) aperture.

Aperture (lat. apertura - hole) in optics is a characteristic of an optical device that describes its ability to collect light and resist diffraction blurring of image details. Depending on the type of optical system, this characteristic can be a linear or angular dimension. As a rule, among the details of an optical instrument, the so-called aperture diaphragm is specially distinguished, which most strongly limits the diameters of light beams passing through the optical instrument. Often the role is aperture diaphragm performs frame or the edge of one of the optical elements (lenses, mirrors, prisms).

Numerical aperture in fiber optic systems - the maximum angle between the axis and the beam, for which the conditions of total internal reflection are satisfied when optical radiation propagates along the fiber. It characterizes the efficiency of input of light rays into an optical fiber and depends on the fiber design.

Entrance aperture - characteristic of the ability of the optical system to collect light from objects of observation . If the object is distant (as with a telescope or a conventional photographic lens), then the aperture is measured in linear form - this is simply the diameter of the light beam at the entrance to the optical system, which is limited by the aperture stop and reaches the image. In telescopes, this diameter is usually equal to the diameter of the first optical element (lens or mirror) in the direction of light. In photographic lenses (especially wide-angle ones), the size of the first lens is, as a rule, much larger than the entrance aperture, and its size should already be calculated. The entrance aperture of a lens is equal to the product of its focal length f' times the relative aperture, or the quotient of the focal length times the f-number. If the object of observation is is close to (like a magnifying glass, a microscope lens or a projector), then the aperture is measured in angular form is the angle of the light beam emanating from the points of the object of observation and entering the optical system.

Exit aperture - a characteristic of the ability of the optical system to collect light on the image . If the image is distant (like that of a telescope, magnifying glass or projector), then the aperture is measured in a linear form - this is the diameter of the light beam at the exit from the optical system, in the zone of the so-called exit pupil . For a telescope (binoculars, spotting scope), the ratio of the input and output apertures is equal to its multiplicity (magnification). If the image is close to (as in a photographic lens), then the aperture is characterized by the angle of convergence of the light beams.

Aperture angle is the angle between the extreme ray of the conical light beam at the input (output) of the optical system and its optical axis.

Angular aperture is the angle between the extreme rays of a conical light beam at the input (output) of the optical system.

Numerical aperture — is equal to the product of the refractive index of the medium between the object and the lens and the sine of the aperture angle. It is this value that most fully determines at the same time the aperture ratio, the resolving power of the microscope objective. To increase the numerical aperture of objectives in microscopy, the space between the objective and the coverslip is filled with an immersion liquid.

Objective aperture - diameter D of the light beam at the entrance to the lens and completely passing through its aperture diaphragm. This value also determines the diffraction limit of the resolution of the lens. To estimate the resolution in arc seconds, the formula 140/D is used, where D is the lens aperture in millimeters.