Many professional photographers use a prime lens for this reason. A prime lens is a camera lens with a fixed focal length. In other words, it can't zoom in or out like a zoom lens can.

This is a Fifth Order lens from the Ontonagon lighthouse. This lens exhibited a red light and as such had a red chimney placed around the lamp inside to make the lens color change. This is what is called a beehive type design. Although some lenses had flash panels installed on them, this one does not. This lens can be seen in downtown Ontonagon at the local museum.

Remember, when adjusting aperture, it's important to keep in mind the shutter speed and ISO settings as well. If you need to increase the shutter speed to prevent blur, you'll need to decrease the aperture to compensate. And if you need to increase the ISO to get a good exposure, you'll need to decrease the aperture as well.

A Fourth Order lens was very typical on the Great Lakes and especially Michigan. A lot of pier head lights and lighthouses displayed one of these lenses. It was a lens size most commonly used throughout the lakes and some ocean coastal harbor stations.

Your lens aperture settings will also impact the depth of field in your photograph. What’s more, changing your aperture will impact what you can achieve with your shutter speed and ISO settings.

So as you can see, changing the aperture has an impact on both the depth of field and the shutter speed. It's important to understand how these two factors work together to create the right exposure for your photograph.

The size of the aperture (the f-stop number) also determines the amount of diffraction that occurs. A small aperture (large f-stop number) will cause more diffraction, while a large aperture (small f-stop number) will cause less diffraction.

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On a DSLR camera, adjusting the aperture is as simple as turning a dial. This adjusts how wide open the lens is, and therefore how much light is allowed in. As we’ve mentioned already aperture is measured in "f-stops", with larger numbers representing a smaller aperture. For example, an aperture of f/22 would be much smaller than an aperture of f/2.8.

Aperture is one of the most important concepts in digital photography, yet it is often misunderstood. Here’s the simple definition: Aperture is the size of the opening in the lens through which light passes.

For example, let's say you're taking a picture of a person in low light with a 50mm lens at f/2. The lowest ISO setting you could use to get a correct exposure would be 3200. If you wanted to use a lower ISO setting, you would need to use a larger aperture (smaller f-stop number). Conversely, if you wanted to use a higher ISO setting, you would need to use a smaller aperture (larger f-stop number).

Reading this post won’t help you master it, though. The best bet is to grab your photo and start experimenting in the real world!

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Depth of field (DOF) is the distance between the nearest and farthest objects in a scene that have crisp details and no unintentional blurring (otherwise known as 'sharp'). It's important to note that depth of field is not an absolute value, but rather it is relative to the distance between the camera and the subject.

The Fresnel lens is the 1822 invention of French physicist Augustine Fresnel who invented a lens that would make his name commonplace along the seacoasts of Europe and North America. Most lenses were handmade and shipped unassembled from France. Others were made in England. Early lens designs resembled a giant glass beehive, with a light at the center (see examples below). The lens could be as tall as twelve feet high with concentric rings of glass prisms above and below a center drum section to bend the light into a narrow beam. Later designs incorporated a bull’s eye design into the center of the lens shaped like a magnifying glass, so the concentrated beam was even more powerful. Tests showed that while an open flame lost nearly 97% of its light, and a flame with reflectors behind it still lost 83% of its light, the Fresnel lens was able to capture all but 17% of its light. Because of its amazing efficiency, a Fresnel lens could easily throw its light 20 or more miles to the horizon.

As you might expect, the larger the aperture, the more light that enters the camera. This is important because it allows you to control exposure.

First, aperture controls the depth of field in your photograph. What is depth of field? It’s the distance between the nearest and furthest objects in a scene that appear ‘sharp’ in an image. The larger the aperture, the shallower the depth of field and the smaller this distance will be. This can be useful for isolating a subject from its background.

So, we’ve talked about aperture and f-stop. But as we mentioned above, changing your aperture settings will likely require you to make some adjustments to the other settings in the exposure triangle.

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That's our post! As you can see aperture is an incredibly important aspect of digital photography. Some of the jargon isn't easy to understand, and probably won't become second-nature until you've had some practice out in the world.

So what is aperture? Here’s a simple definition: Aperture is the size of the opening in your camera lens (the word is literally a fancy way of saying 'opening). This determines how much light enters your camera and hits the image sensor.

A First Order lens found at the Ponce De Leon Inlet Lighthouse near Daytona Beach Florida. No First Order lenses were used in the Great Lakes. These lenses are huge!

The size of the camera aperture (the f-stop number) determines the amount of depth of field in an image. A small aperture (large f-stop number) results in a large depth of field, while a large aperture (small f-stop number) results in a shallow depth of field.

Bokeh can be used to create a dreamy or romantic look, or to make the subject stand out against a busy background. It is also often used in portraiture to help the subject stand out from the background. Bokeh can be created with any type of camera, but it is most commonly associated with DSLRs and mirrorless cameras.

Generally speaking, a higher f-stop number will result in a photo with a small area in focus and a large area out of focus. On the flip side, a small f-stop number will result in a photo with a large area in focus and a small area out of focus.

Generally Fresnel lenses are divided into 7 classes (called “orders”). The order is determined by the distance of the flame to the lens. The “First Order Fresnel lens” is the largest lens widely used, and was installed in many of the largest “sea coast lights”. Two larger sizes were built in limited quantity and they are the for a couple of special installations. Smaller Fresnel lenses, such as the sixth-order lens, were installed in smaller lighthouses, such as breakwater lighthouses. See the chart below of lens orders which represents standard beehive type designs in general and not varying at all in characteristics..

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*Source: Guardians of the Golden Gate: Lighthouses and Lifeboat Stations of San Francisco Bay Ralph Shanks and Lisa Woo Shanks, editor. 1995, Costano Books, ISBN: 0-930268-08-3.

For example, let's say you're taking a picture of a person with a 50mm lens at f/2. The amount of diffraction would be minimal. If you wanted to use a smaller aperture (larger f-stop number), the amount of diffraction would increase.

Diffraction is an optical effect that occurs when light waves pass through a small opening. The result is a loss of sharpness in the image.

Second, exposure isn't only set by your aperture. Your shutter speed and ISO settings also affect exposure, and you'll need to do some trial and error to figure out how to get the exposure you want. That’s why people call these three settings the ‘exposure triangle'.’

This Sixth Order lens is the smallest of the lenses made for lighthouses. It was designed for small light stations or pier head type lights. This one is on display inside the Saulte Saint Marie Coast Guard Station. These lights were common in the Great Lakes on small harbors or piers.

Fresnel light

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Most DSLR cameras from companies like Nikon and Canon will have a lower f-stop number (or maximum aperture) of f/1.4. This a very wide aperture opening, and will let in a lot of light.

Aperture is one of three camera settings — along with ISO and shutter speed — that impact how well (or not) your photo is exposed. These three settings are often called the ‘exposure triangle.’

As we've explained, changing the aperture can have a big impact on your image. But how do you know which aperture to use? Well, it depends on the look you're going for.

Prime lenses are often used for portrait photography, who want to capture clean, sharp images with minimal distortion. Prime lenses are also often used by landscape photographers. While they generally require the use of a tripod or other stabilising device due to their narrow field of view, prime lenses offer a number of advantages that make them a popular choice among professional photographers.

The size of the aperture (the f-stop number) also determines the ISO that's needed to achieve a correct exposure. A small aperture (large f-stop number) will require a lower ISO setting, while a large aperture (small f-stop number) will require a higher ISO setting.

Let’s tackle shutter speed first. Now, what is it, exactly? Shutter speed is the amount of time the shutter is open and exposes the camera's sensor to light. The longer the shutter is open, the more light that enters the camera.

That’s right: you can change the amount of light (aperture) and the sensitivity to light (ISO). As you can imagine, changing one of these settings is likely to impact how the other works.

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Our advice: read this guide, take your camera off auto mode, and then start taking some photos of your own (maybe for your next photo essay). It might be worth bookmarking this page, taking some photos, and then coming back for another read.

If you want to isolate your subject from the background (or foreground), then you'll want to use a large aperture (small f-stop number). This is known as shallow depth of field, and it's often used in portraits and close-up shots.

This is a Third Order lens. This lens is a fixed lens and not meant to be rotated. Some of these lenses are on display around Michigan Museums. This one is the Big Bay Point lens on display in Marquette.

It sounds complicated, and some of the terminology ('f-stop', ‘bokeh’) doesn't help! But as with most aspects of photography, it all gets a lot simpler after you start experimenting with different apertures in the real world.

A Second Order lens from Standard’s Rock lighthouse in Lake Superior. One of only a small handfull of this size lenses used in the Great Lakes. This one has bull eyes in the center and is meant to create a flash pattern as it is rotated.

Aperture is measured in an f-stop number. The lower the f-stop number, the more open the aperture is and therefore more light enters your camera. The higher the f-stop number, the more closed down (or smaller) the aperture is and less light enters your camera.

This mode is also sometimes called "semi-manual" mode because the photographer still has some control over the exposure. For example, if the scene is very bright, the photographer can choose a small aperture to avoid overexposing the image. Conversely, if the scene is darker, a larger aperture can be used to let in more light. Aperture priority is a popular mode for many types of photography, including portrait, landscape, and still life. It is also a good choice for beginners who are not yet comfortable with manual mode.

Here's an example to illustrate how this works. Let's say you're taking a picture of a flower garden with a 50mm lens at f/8. The depth of field would be approximately 2 feet (0.6 meters). This means that objects within 2 feet of the camera would appear sharp, while objects beyond that would start to become blurry.

This Third and a Half Order lens was one typically built for service on the Great Lakes as it was a medium size between a Fourth and Third Order lens, a Fourth was to small and a Third was just to large for the intended use. This is a fixed lens and not a rotating lens. This is the Gray’s Reef lens and can be seen at the Charlevoix Historical Society Museum.

The size of the aperture (the f-stop number) also determines the minimum focus distance of the lens. The minimum focus distance is the closest distance that the lens can focus on an object and still produce a sharp image.

It's important to understand that aperture is not a setting on your camera, but rather a characteristic of your lens. The aperture is determined by the physical size of the diaphragm, which can be changed by swapping out lenses or adjusting a zoom lens.

Bokeh is a technique in photography that is used to create a soft, blurred background. This effect is achieved by using a large aperture and keeping the subject in focus while the background is out of focus.

Fresnel Effect

What about the third part of the exposure triangle, ISO? ISO is a measure of the camera's sensitivity to light. The higher the ISO number, the more sensitive the camera is to light. This means that less light is needed to achieve a correct exposure.

If you want everything in your image to be sharp and in focus, then you'll want to use a small aperture (large f-stop number). This is often desirable for landscape shots, group photos, and other situations where you want everything to be sharp.

The f-stop number is calculated by dividing the focal length of the lens by the diameter of the aperture. For example, if a lens has a focal length of 50mm and an aperture diameter of 25mm, the f-stop would be 2 (50/25).

Now let's say you take the same picture with the same lens, but at f/2. The depth of field would be reduced to about 0.6 feet (0.2 meters). This means that only objects within 0.6 feet of the camera would appear sharp; anything beyond that would be significantly blurred.

As a result, prime lenses typically have a wider maximum aperture than zoom lenses, making them well-suited for low-light photography and achieving shallow depth of field effects. The wider aperture also allows for greater control over the placement of focus within the frame.

There are many sizes of Fresnel lenses, called ‘orders’, the largest being a first order, which is made up of hundreds of glass prisms. The lenses decrease in size through second order, third order, etc. Some have red panels, in order to shine a red light seaward. The glass prisms are shaped and positioned in such a way that the light from the single source inside the lens is reflected outward horizontally through each prism. In this way, the light streaming outward in all different directions is maximized into large beams shining out to sea. The number of beams depend on the configuration of the prisms, which can vary greatly. Different lighthouses must display beams for differing periods of time in order to be distinguished from one another.

Aperture priority mode allows the user to select the aperture while the camera sets an appropriate shutter speed. Aperture priority is often abbreviated as "A" or "Av" on camera mode dials.

The size of the aperture (the f-stop number) also determines the shutter speed that's needed to achieve a correct exposure. A small aperture (large f-stop number) will require a longer shutter speed to achieve the correct exposure, while a large aperture (small f-stop number) will require a shorter shutter speed.

Early Fresnel lenses were of standard shapes and designs with little deviation such as the one pictured above. They had an oil lantern that burned constantly from dusk until dawn with no flashing or blinking as you may think of them today. Once they started being used along the coasts in greater numbers the mariner could not tell where they were at night because nothing distinguished one light from another. For a lighthouse to be effective as an aid to navigation, it not only had to be seen, it also had to be identified as a unique location. This was necessary if ships were to use it to determine their own location and avoid hazards. From here on out different lenses were made with different characteristics and as such required different lens designs. This meant that a lot of lenses were now unique because they would require flash panels or bull’s eyes to distinguish one light from the next. The need to clearly identify each lighthouse was often solved by a specific pattern of flashes per minute. Although sometimes lighthouses identified themselves by using colored light, most made use of a flash of light, followed by a period of darkness. This pattern was called the lighthouse’s “characteristic.” Once electricity was introduced a light could use a flashing mechanism to give it a unique characteristic flash pattern. Now a sea captain could tell where he was by looking at a map and the flash pattern of the light and tell he was in Maine or Massachusetts.