What is Aperture Size

Many beginner photographers often ask what is aperture size? What does the aperture setting do? How does aperture effect my photos? What determines the size of the aperture size I can use? In this photography tutorial on aperture size you will learn all about changing your exposure using aperture.

What is Aperture Size

Aperture size is the size of the path that allows light in through your lens into your DSLR camera to the DSLR camera’s sensor. This is also the same as film cameras, but instead of letting light into your camera to the camera sensor, aperture is the size of the path that allows light in through your lens into your camera to get to the film.

How Does Aperture Effect Photo Exposure

Aperture size can effect your photo’s exposure by letting in more light through the lens, or less light through the lens, which will effect your photo’s brightness. If you want a brighter photo you need to let in more light. Unlike shutter speed, the aperture doesn’t change the amount of time the shutter is open, but how big of an opening light can pass through. So if you need more light to get a brighter photo, but don’t want to lower your shutter speed and chance making your photo motion blurred, you can open your aperture more to allow more light into the camera.

Aperture size setting of a camera will also effect your depth of field. Which you can read about depth of field in another article, to make depth of field in a short summary it is how much depth is in focus. Just the person you are focused on, or the person behind them as well. This is how photographers blur backgrounds in portraits is using a low or short depth of field so the subject is in focus, but nothing else. Using a larger aperture (lower number) the larger the opening, the less depth of field, the more only the subject is in focus. The smaller aperture setting you select (larger number) the smaller the opening, the more other objects become in focus, not only the specific subject you are focusing on.

What Determines the Size of my Aperture

The lens you have attached to your camera determines the size of your aperture. Most lenses have a range of the maximum aperture size they use between the different focal lengths the lens is capable of. Some lenses may only have a single maximum aperture size on them which means you can use that size at any focal length the lens is capable of. Aperture size is usually printed on the lens and represented with an “f”.

A Sigma 50-150mm f2.8 lens is capable of an aperture size of f2.8 throughout the entire focal range of the lens 50-150mm. So whether you are zoomed out 50mm you can use aperture size of f2.8 or you can zoom in a little to 80mm and still use the same maximum aperture size of f2.8, or you can even zoom in all the way to 150mm and still use f2.8 aperture size as your maximum aperture size. Lenses with a large aperture f1.2, f1.4, f1.8, and f2.8 are considered “fast glass” or “fast lenses” as they can let in a lot of light. Don’t ask me where they got the name “fast lenses” as I would have just called them “big hole lenses” or something. Bigger aperture sizes on these types of lenses are usually more expensive.

A Canon 75-300mm f4-5.6 lens is only capable of a maximum aperture size of f4 and only if you are zoomed out at 75mm, the more you zoom in the lower your maximum aperture size gets. If you zoom in all the way to 300mm you will only have a maximum aperture size of f5.6.

On both of the lenses mentioned above you can always use a smaller aperture if you choose to. You can take the aperture size all the way to f22 and have a pin hole letting light into the camera.

When do I Want to Use a Large Aperture

You will want to use a larger aperture lens/setting in the following:

  • Use larger aperture in low light where you don’t want to use a flash, flash is not powerful enough, or flash causes harsh lighting/distractions, such as indoor weddings.
  • Use large aperture in portrait type photos where you want to have your subject in focus and background blurred/boken.
  • Use a large aperture in photo shoots that you want a slightly softer look to your photos.

When do I Want to Use a Small Aperture

You will want to use a smaller aperture lens/setting in the following:

  • Use smaller aperture in landscape photos, get every object in focus.
  • Use smaller aperture in group photo shoots, get each person in every row in focus, not just row 1 or just row 2 people.
  • Use a smaller aperture in photos that you want more detail and sharpness.

I hope this photography exposure tutorial on aperture size has helped you understand aperture or at least understand aperture more than you did before you read this information on aperture size. If you have any questions, comments, and/or suggestions about aperture size please post it below!


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