Everything you need to know about aperture

What is Aperture?

Aperture is how big the opening is and this affects the amount of light to enter and the depth of field.  As you can see from below the bigger the opening the smaller the number. (I know it’s annoying, but thats just the way it is) 


How is aperture measured and changed?

Aperture is measure in f stops. 

I know what your thinking why can’t the numbers go up as the opening gets bigger. I thought the exact same thing when I first started, unfortunately, Its a mathematical thing, and maths was never my favourite subject. What you need to know is that from each number to the next, the aperture decreases to half it’s size, allowing 50% less light through.

Most DSLR go up in increments of one third of a light stop. as shown below. Moving from f2.8 to f4 is a whole stop of light, but you could move a 1/3 of a stop from f2.8 to f3.2.

1.0, 1.1, 1.2, 1.4, 1.6, 1.8, 2.0, 202, 2.5, 2.8, 3.2, 3.5, 4.0, 4.5, 5.0, 5.6, 6.3, 7.1, 8.0, 9.0, 10.0, 11.0, 13.0, 14.0, 16.0, 18.0, 20.0, and 22.0.

The easiest way to show you how this effects your exposure is to show you. 

Can you see how the bigger the opening the more light comes in, Good. 

Now to the fun bit, because Aperture isn’t about just exposure its about depth of field. (This is how blurry your background it)

How Aperture effects depth of field?

Depth of Field is how much is in focus. A shallower/ Narrower depth of field (DOF) means less will be in focus. Life the top row. in order to achieve this you need a wider/ aperture, like f2.8. 

However, you want more of the background in focus, you will need to increase your depth of field and therefore need a narrower aperture like f/22

Can you see the difference?

So which f stop do you need?

There are no set rules on this one, but what I will say is that here are a few starting points. 

f/1.4: This is great for shooting in low light, but be careful of the shallow depth of field, because it can be too shallow. 
f/2.8- f/4Still good for low light situations, but allows for more definition in facial features as it has a deeper depth of field. Great for close up single person portraits.

f/5.6: Good for photos of 2 people, not very good in low light conditions though. So either use a reflector or bounce some flash. 
f/8: My street mode, I use f/8-f/11 when out and about.
f/11: This is often where your lens will be at its sharpest so it’s great for portraits, if you’ve got a clean or story telling background. 
f/16: Shooting in the sun requires a small aperture, making this is a good ‘go to’ point for these conditions.
f/22: Best for landscapes where noticeable detail in the foreground is required.


Still confused??? That's ok. Why not drop me a question below.


  1. this is soooo useful! Until today, I was completely unaware of this. You explain it so well! I have a question though. It might be silly, but oh well. Does the same apply to videos too?

    I have seen various videos where the fairy lights in the background are kind of out of focus. How do we achieve this with a DSLR in video mode?

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