Understanding aperture in photography is key to creating great photos. One of the most important considerations is the difference between “maximum aperture” and “minimum aperture.” You’ll constantly hear photographers use these terms, but they can sound like gibberish if you don’t have the right background knowledge. So, today, I’ll explain the importance of the maximum and minimum aperture values on your camera’s lens.
What is Aperture?
The question of maximum and minimum aperture starts with understanding what aperture means in the first place! The aperture is part of your camera’s lens. Specifically, it’s the opening in your lens that changes size, which can increase or restrict the amount of light passing through. Your aperture looks like this:
This opening’s size is controlled by the aperture blades, which are little overlapping flaps inside your lens, as you can see above. The blades open and close as you change your aperture setting.
How do you change your aperture setting? It depends on the camera equipment that you’re using. Some lenses let you control the aperture manually, by rotating a ring on the lens. On the other hand, many modern lenses simply control the aperture setting via an electronic or mechanical connection with the camera body. So, you just rotate the appropriate dial on your camera instead.
Aperture values, typically given as an f-stop (like “f/2.8”) indicate how big or small that opening is relative to the focal length. A classic analogy compares the aperture to the pupil in your eye. In bright light, your pupil gets narrower, reducing the amount of light that comes into your eye. Meanwhile, in a dark environment, the pupil opens up, letting more light in.
Aperture is written as a fraction. That’s why an aperture of f/4 can be thought of as “1/4th,” while an aperture of f/16 can be thought of as “1/16th.” Thus, it is easy to see why an aperture of f/4 would be considered larger than an aperture of f/16. It’s no different than the number one-fourth being larger than the number one-sixteenth.
What is Maximum Aperture?
The maximum aperture is the widest your lens’s aperture blades can open, and is therefore the most amount of light that can be let through. Maximum aperture is a property of your lens, not your camera. If you change lenses with a DSLR or mirrorless camera, you can dramatically change your maximum aperture.
Typical maximum apertures for lenses include f/1.8, f/2.8, f/3.5, and f/4. Apertures let in approximately the same amount of light from lens to lens – so if you set two different lenses to, say, f/4, your photos will have a very similar exposure. Note that on almost every lens, you can change the size of the aperture and set it to many different values. The “maximum aperture” is simply the widest of these options – maximizing the amount of light you capture.
Photographers often pay a lot of money for lenses with the widest possible maximum aperture. That’s especially true of f/2.8 lenses in the case of zooms, and f/1.4 lenses in the case of primes. A few zooms even go to f/2 or f/1.8, and prime lenses occasionally reach crazy maximum apertures like f/0.95! These are usually very specialized lenses, however. They are good for shooting in extremely low light conditions or taking photos with a very shallow depth of field.
Here’s how a lens looks at its maximum aperture (a whopping f/0.95 on this specialty lens) – note that the aperture blades are open so wide, you can’t even see them any longer:
It isn’t easy to make lenses with a very wide maximum aperture, which is why you’ll rarely see f/0.95 or f/1.0 lenses. A larger aperture requires bigger glass, specialty lens elements, or other expenses to ensure that it delivers the same optical quality.
Instead, most lenses have a maximum aperture that’s closer to f/2.8 or f/4. Those maximum apertures aren’t as bright as something like f/1.0 or f/1.4, but they still allow you to capture a reasonably high amount of light in dim environments.
What Effect Does a Wide Aperture Have on a Photo?
When you set a wide / large aperture on your lens, the most immediate effect is the change in exposure. Wide apertures let through more light, and if you kept your ISO and shutter speed the same, your image is now brighter than it was at a smaller aperture setting.
Wide apertures are therefore very helpful in low light conditions. You’ll have a much easier time photographing dim subjects like Milky Way photography with an f/1.4 or f/1.8 lens, compared to a lens whose maximum aperture is f/4 or f/5.6.
To be clear, in many low light situations, you’ll have to balance your aperture with the other camera settings of shutter speed and ISO. Those aren’t the topic of this article, but I don’t want you to think that aperture is the only thing that affects the exposure or brightness of an image.
Beyond the impact on exposure, a larger aperture setting also reduces depth of field. While we have a more in-depth guide to depth of field here, the brief summary is that the depth of field is the zone of sharp focus. A wide aperture gives you a shallow focus effect with a narrow depth of field. This can help you get a pleasant blur on a portrait, for instance. Yet another reason to get a lens with a wide maximum aperture!
Sometimes, you won’t want a shallow depth of field like this. If you want to see more of the background, you can gain depth of field with narrower apertures like f/8 or f/16. It’s an artistic choice. But if you have a lens with a wide maximum aperture like f/1.4, you have more artistic choices available to choose from :)
What is Minimum Aperture?
While the maximum aperture is the largest the opening in your lens can be, the minimum aperture is the smallest/narrowest. A typical minimum aperture value on a lens is f/16 or f/22, but other lenses can go even smaller.
At these very small aperture values, very little light is getting through your lens. You will also get a much greater depth of field, which is desirable for something like landscape photography.
Unlike the maximum aperture of a lens, photographers usually don’t care too much about minimum aperture. Why not? Well, f/16, f/22, f/32… it’s all the same at a certain point. These apertures don’t let in much light, and they give you a lot of depth of field.
There’s also the fact that narrower apertures increase the effect of diffraction, which is a phenomenon in optical physics that makes your photos less sharp. Every lens suffers from diffraction. But especially at f/16, f/22, and certainly f/32, diffraction can really harm the sharpness of your photos. So, photographers don’t have much of an appetite for minimum apertures anyway.
That’s why the minimum aperture may not even be apparent if you read the name of a lens. Photographers care very much about maximum aperture, so it’s almost always put in the name of the lens – like the “Nikon Z 24mm f/1.8 S.” You already know from the lens name that it can reach f/1.8 at the maximum, but you’d need to pull up Nikon’s website on the lens to see that it tops out at f/16 on the narrow end.
What Impact does a Small Aperture Setting Have on My Image?
A very small aperture has the opposite effects of a large aperture. It lets less light through your lens, making the exposure darker when your other camera settings are kept constant. It increases your depth of field, which is usually great for landscape photography.
Because exposure in photography is a balance of different settings, you can use narrower apertures to your advantage creatively. For example, if you’re photographing a waterfall, you may want a smooth motion blur effect in the water. If so, you can set a narrow aperture (like f/18 below) to force a longer exposure time and smooth movement of water, clouds, or other subjects, even in bright conditions.
A small aperture can also give you more depth of field, as I’ve mentioned a few times. For something like macro photography, small apertures are vital. At extreme close focus distances, you lose a lot of depth of field, and even getting a tiny bug to be in focus all at once can be a challenge! I routinely use narrow apertures like f/11, f/13, or f/16 for close-up photos like the one below.
Even then, I rarely ever worry about the minimum aperture of my lens. Dedicated macro lenses have tiny minimum apertures like f/32, f/45, or f/64. And for other types of photography, it’s just not going to be an issue – there will not usually be cases when you need anything narrower than f/16.
What’s a Variable Aperture Zoom Lens?
A variable aperture zoom lens has a different maximum aperture at different focal lengths! Variable aperture lenses are always zoom lenses. For example, the Nikon 18-55mm f/3.5-5.6 lens is a variable-aperture zoom lens. It reaches a maximum aperture of f/3.5 at the widest focal length of 18mm, and a maximum aperture of f/5.6 at the longest focal length of 55mm.
Many zoom lenses, typically less expensive models, have a variable aperture. This range will look like f/3.5-5.6 or f/2.8-4. As you zoom in, you lose the ability to set the widest aperture of f/3.5 or f/2.8.
By designing a variable aperture zoom, lens makers can reduce cost, complexity, or size of the lens. As a photographer, variable aperture lenses can work great, but it’s important to keep in mind that you will have fewer aperture options towards the long end of the zoom range. That’s why most pro-level zooms have a constant aperture, like the Canon RF 24-70mm f/2.8L or the Nikon Z 24-120mm f/4 S.
On the opposite side of the spectrum, a small number of lenses have a permanently fixed aperture that cannot be changed at all. This includes most cell phones, some drone cameras, and a few specialty “mirror” telephoto lenses. But these are exceptions. Almost all lenses for DSLR and mirrorless cameras have a range of aperture values you can select from.
How Is a T-Stop Different from Aperture?
Finally, you may have heard of a measurement called “t-stop” that is different from “f-stop.” A lens may be referred to as T3.0 instead of f/2.8, for example.
Although this is more common in the world of videography, T-stop refers to the actual transmission of light through a lens, whereas f-stop is a “best-case” number based on the physical size of the aperture in the lens.
While this distinction is typically small and immaterial to most photographers, it can affect your exposure in some special cases. One of the most significant instances is on the very premium Canon RF 85mm f/1.2 DS lens. The DS refers to special technology on the lens that makes out-of-focus backgrounds look more pleasant, at the expense of about 1.3 stops of light. The depth of field is still the same as an f/1.2 lens, but the 85mm f/1.2 in question only allows as much light as a typical f/2.0 lens. So, the t-stop is said to be T2.0.
There’s a tradeoff behind every decision in creating a photograph, and your choice of aperture setting is a perfect example of that. It helps to understand your aperture’s limits, though: the maximum aperture that lets in as much light as possible, and the minimum aperture that is as narrow as the lens gets.
By understanding maximum and minimum aperture, you’ll have a better idea of what lenses to get and what photos you’re able to take with a particular piece of gear. I hope this article helped you figure that out! Let me know in the comments below if you have any questions about maximum or minimum aperture as a photographer.
Concerning depth of field and bokeh, some lenses have severe field curvature which can influence the depth of view in a positive or negative way. Depending the way it curves it can also influence bokeh in a negative way . The vintage Minolta Rokkor VFC 24 mm had even an adjustable field curvature option :-) to obtain more depth of field. Cameras with a thick filterstack like the Sony A series tend to cause field curvature and some other aberrations with most vintage lenses shorter than 50 mm and in some cases you will never obtain ideal results.
Thank you. What effect does the number of blades have on the image? Some lenses have more blades than others. Is more better? Fewer better? Is there an ideal number of blades? Does it matter how many blades in relation to the lens size – 35 mm; 50 mm; 200 mm? Thank you.
More blades means out of focus bokeh circles are more rounded, and more pleasing to most people. Many newer lenses have rounded blades, which also contributes to the roundedness of the bokeh circles. If the blades are not rounded, the bokeh circles will appear as polygons, e.g. 6 blades will show hexagons or approximations of hexagons which can be unsightly.
Many wider-angle lenses like 20mm can produce sunstars (makes the sun look like a pointed star). In that case, if there are an even number of blades you get that number of points in your star. 6 blades -> 6 pointed star. An odd number of blades gives twice the number of points. e.g. 7 blades -> 14 pointed star.
closing aperture is a journey down the hill with chromatic aberration and up the hill with diffraction, where the valley is your sweet spot when you take sharpest images 😊
That’s an interesting way of thinking about a few of those aspects of aperture. I think with many modern lenses, the key question is really what aperture gets you the right depth of field for the image – rarely do I see an image where sharpness, CA, or diffraction is more of a problem than missed focus or DOF related issues.
That is absolutely true, Alex! I’m surprised at how much I can stop down sometimes and still get a decent image. Where I have noticed it is extreme macro where the depth of field is very small and the actual aperture is even smaller than the aperture you set the camera at. In that case diffraction seems quite apparent at smaller apertures, so I guess that’s one of the many reasons why stacking is so common.
Only the axial aberrations are reduced by stopping down the lens, e.g., spherochromatism (colloquially know as “purple fringing” and “longitudinal CA”): wavelength-dependent spherical aberration.
Transverse (aka lateral) chromatic aberration is therefore not reduced by stopping down, but it is trivial to correct in software.
Unless you are photographing only flat test charts, I suggest reading the following science-based article:
How to Choose the Sharpest Aperture by Spencer Cox
300 F/4 lens @ F/4 has entrance pupil diameter of 75 mm whereas a 40mm F/2 lens @ F/4 has entrance pupil diameter of 10mm. This explains depth of field difference between the two.
Is there a correlation between 75mm and 10mm when it comes to DoF as well?
Like, the 40mm lens @ F/4 will have (75/10) = 7.5 times DoF at “closest focussing distance” than the 300mm F/4 @ F/4?
I’m not really sure that 7.5 figure is directly useful for photography. While I can’t speak to the physics of lens design, I think having an intuitive understanding of longer lenses and larger apertures translating to thinner depth of field, followed by a decent understanding of the “look” you can get with the lenses in your bag is sufficient. I’m curious if anyone has a more mathematical answer for you.
I hope you find the following of interest…
If one uses, say, a 50 mm at f/5.6 to take a portrait, then one stands ten times the distance away from the subject using a 500 mm lens at f/5.6:
• the subject-to-image magnification ratio will be the same;
• the depth of field will be nearly the same;
• the effect of diffraction on the subject will be the same (in both object space and image space).
Obviously, the diameter of the circle of confusion on far background objects (the amount of background blur) will be in the region of ten times the size using the 500 mm because these background objects, being comparable distances away from each lens, will be magnified ten times compared to the 50 mm lens.
In object space an ideal (diffraction-limited) optical system has an angular resolution determined by the diameter of its entrance pupil. In our example above, the 500 mm lens entrance pupil has ten times the diameter of the 50 mm lens, giving it ten times better angular resolution, but it is ten times the distance from the subject, therefore (because the angles involved are small) the spatial resolution, at the subject, is the same for each lens. Similarly for the depth of field.