What is called maximum aperture is how wide your lens aperture can be.
A lens with wider aperture allows you to let in more light to your camera sensor, so you can take pictures in dimmed light environment better.
Wide aperture lens also called a fast lens, because of using their wide aperture you can take pictures with faster speed.
But it doesn't mean that you should always get this type of lens. Depending on your needs, don't get the lens with wider aperture than you need. It will cost you more.
Let's talk about aperture first.
What is aperture ?
In simple words, aperture is a hole with variable diameter inside the lens that control how much light that you want to let in.
It symbolize with "f/[number]". For example f/3.5, f/8, etc.
You should note that the bigger the f/ number, the smaller the hole, and the smaller the f/ number, the bigger the hole.
You can see the illustrated picture below:
When someone told you to use big aperture or small aperture, you may confuse with the word "big" and "small", you don't know which one you should look, the f/ number or the real hole opening.
Don't be confused, always remember this, when someone said big or small aperture, it means the real hole opening not the f/ number.
Using the illustrated picture above, big aperture means you should use f/2, f/2.8. And small aperture means you should use f/11, f/16.
Like I said in the first line of this post, the limit to how wide a lens can be opened is called the maximum aperture.
All lens aperture can be set to open in f/11, f/16, f/22.
But you should know that not all lens can be set to open in f/1.4, f/1.8, f/2, f/2.8.
Most standard kit lens can be set to open maximum in f/3.5.
This limit is what is called maximum aperture for that lens.
What are the benefits of lenses with wide maximum apertures ?
Taking Photo With Natural Light
When you need to take photo in dimmed light environment you have two option, using flash or without flash but with a slow speed that can make your picture blurred.
If you use flash, you may ruin the mood of the picture. But if not using flash, your speed is very slow that you may need a tripod.
When you have lens with maximum aperture f/1.8 or f/2, it will help you take pictures in that condition. Because the aperture let in more light, you can use faster speed even with no flash. So you can take photo with natural light available and reduce the blurred image because of using slower speed.
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Faster Shutter Speeds
Like I already written above too, the use of wide aperture prevents blurred image, because you can use faster shutter speeds.
You want to take your children photo, playing in the garden, they are running everywhere.
with f/4 you get speed at 1/100s. When you switch to f/2 you will get speed at 1/200s.
Shallow Depth of Field
Lenses with wide maximum apertures have shallow depth of field.
This is useful when you want to isolate your photo subject from the crowded background.
Nature and portrait photographers usually use this the most.
Take a look at this photo:
Taking with f/1.8
Taking with f/4.5
How to Read Maximum Aperture of a Lens
When you look at the lens you will see some reading like this:
- 50mm f/1.8
- 18-55mm f/3.5-5.6
- 70-200mm f/2.8
The first one is a Prime Lens, because it has fixed focal length, 50mm. And the second one is Zoom Lens, because it has variable focal length, 18-55mm.
The reading after the focal length is that lens maximum aperture.
For the prime lens above the maximum aperture is f/1.8. And for the Zoom Lens it is range beetween f/3.5-5.6.
It means when you set the focal length at 18mm, the maximum aperture ypu can set will be f/3.5.
And when you set the focal length at 55mm, the maximum aperture you can set will be f/5.6.
When using this type of zoom lens, your exposure settings will keep changing along with you zooming in or out, because the aperture constantly changing.
There are also zoom lens with a fixed aperture, such as in the example above, 70-200mm f/2.8. It means the maximum aperture won't change all across the focal length you use.
This lens will cost you more, because it combines the benefit of variable focal length that Zoom Lens have, and the fix aperture that Prime Lens have.
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So, here's a quick guidance for what maximum aperture you need:
- Daylight (outdoor) = Any apperture, in broad daylight it doesn't matter what the max aperture of the lens.
- Indoor = f/1.4 - f/2.8, If you want to take pictures indoor without flash.
- Cloudy (outdoor) = f/2.8 - f/3.5, When you want capture fast moving subject in a cloudy day.
- Shade (outdoor) = f/3.5 - f/5.6, When it is not as dim as cloudy day.
Next article is about choosing between first or third party lenses.
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