What is aperture in photography
Aperture is a hole on the lens diaphragm when we make the picture, where the light comes in. We can adjust the hole size on the camera with usually the dial near the shutter release button. We can speak about big, small and middle apertures. The hole only gets smaller for a very short period when we release the shutter release button, and actually make the photo. Otherwide we see through the open aperture (the biggest opening). The thing that is control the size of the aperture inside the lens we call aperture blades or iris.
No of aperture blades or rounded or circular aperture
The lens on the below pictures (Canon 200mm f/2.8L) has 8 non circular aperture blades. If we stop down the lens (select smaller apertures) the shape of the hole can be different, in this case octogonal. In case of newer lenses usually the internal contour of the aperture blades are circular (round hole) not octogonal like here. Where is this interesting ? If we make pictures with highlights in the background the highlights will have the format of the hole. Wide open the highlights are circular.
You can see apertures of f/2.8 f/4 and f/5.6 at the below pictures, from left to right direction
when the hole is big, but the number is small f/1-f/2.8
when the hole is small, the numbers are big, like f/11-f/16 -f/64
From f/4-f/8. Here the hole is in the middle, the number as well. These are the most useful apertures regarding picture sharpness.
How to name the different apertures
The usual name is like this: f/4 or 1:4 as you can see on some lenses. But many times they left the / or : sign just say f4, f8 but it means the same, to more deeply understand, the aperture refers to the area, and how much light come in. If you divide something with bigger number the result will be smaller, and other way as well, if you divide with a smaller number the result will be bigger.
How to adjust aperture ?
Different cameras are different in this regard, but there are some common things as well. First must turn the dial at the top left part of your camera to A or Av (aperture priority mode). After you turn the dial next to the shutter release button and the back screen or if you have on the top LCD you see the numbers changing. There are two numbers: the shutter speed and the aperture. At the above picture the aperture is on the top right corner after the letter ” f “. If you turn the front dial you see the number changing depending on your lens attached usually between f/1.4 on f/22 most cases. The smallest number is the brightest aperture of the attached lens. At the same time you see the shutter speed as well, here left from aperture 5″(5 seconds) which is depends on aperture and available light quantity. 1/3s shutter speed showed 3, 1/30s showed 30, 1/400s shutter speed is just market 400, 1/1000s 1000 and so on. If the shutter speed is longer you see 1” (1sec), or 30″(30sec). If your camera has a top LCD you also search for two numbers. Usually the right one is the aperture, the left one is shutter speed.
What is aperture good for?
The aperture does two things:
1. Define image sharpness
– most lenses are not sharp at their brightest aperture, we call the process of using smaller apertures “stop down the lens” to smaller apertures. The sharpest apertures usually called “sweet spot” it is usually f/5.6 for most lenses, some lenses are sharper at f/8 or f/8. Smaller apertures are usually not so sharp because of the phenomenon called diffraction.
2. Control depth of field
usually referred as DOF. If we want huge depth of field like in landscapes (everything in focus) or macro we use small apertures like f/8-f/22. If we want to blur the background, or want to have high shutter speed to freeze action like in portraits, sports or birds/wildlife for example we use big apertures like f/1-f/2.8-f/4, depends on the lens as well. Usually longer lenses are darker, because these lenses lets less light in, they are not really available in the f/2 range and f/2.8 or f/4 versions are extremely expensive. So usually we have f/5.6-6.3 lenses for wildlife but not all of these lenses are sharp wide open at f/5.6, usually must stop down to f/8 to have exceptable sharpness for distant tiny bird pictures. In theory we want to use the brightest aperture to create high shutter speed needs for sharp shots in the distance.
The usual aperture range goes like this:
1 1.4 2 2.8 4 5.6 8 11 16 22 sometimes can be f/32 or f/64 as well
If you check this there is app. 1.4x multiplying between the numbers. With this 1.4 pairs the difference is a doubles shutter speed. What does it mean? If you make the hole bigger on your lens, let’s say use 2.8 aperture instead of 4 this means, you double shutter speed of your camera, which is useful in low light or if you want sharper images.
The lens maximum aperture
Every lens has a maximum aperture, zoom lenses sometimes has two maximum apertures. This number is usually written on the lens like 1:1.4 or f/5.6. The maximum aperture refers to the maximum amount of light the lens can let in the camera. We speak about slow and fast lenses. Fast lenses when the aperture is big, for example f/1.4 or f/2.8, slow lenses when the aperture is small like f/5.6-f/6.3. Darker lenses like f/8 are not very useful in Dslr photography because lets very few light in resulting a dark viewfinder. Obviously fast lenses usually need bigger size to let more light in. What if the lens has two number, for example Canon 18-55mm f/3.5-5.6. The first two number is the lens focal length: 18mm is a wide setting, 55mm is a longer setting. The first number of the two second number(3.5) refers to the widest setting the other(5.6) refers to the telephoto setting. The value can change between as well, for example 35mm can be f/4.5. Usually longer lenses lets smaller amount of light in.
Which lenses are better
Regarding aperture brighter faster lenses are preferred over the darker, slower lenses, but these lenses are usually much more expensive. On the other hand if the lens is brighter and faster doesn’t necessarily means it is sharper. Dark lenses can be very sharp as bright lenses can be unsharp as well.
Assignment is not obligatory, but can help to practice what you have learned.
Make pictures with different apertures (the brightest you have, f/4 f/8 f/16 f/22) about the subject which is approximately 0.5-1m (1.5-3 ft) from your camera, and study the pictures you made. If the image with small apertures comes blurred, use higher iso settings. What do you learned?