Knowing Aperture and How To Use It

Knowing Aperture and How To Use It

In my earlier article – Digital SLR Beginner – Understanding Shutter Speed, Aperture and ISO, I did a brief explanation on what APERTURE is like and how it works in controlling the amount of light that enters your camera.

In this article, I will expound more on what is aperture and I will also be showing you how aperture can be used to achieve beautiful effects for your shots.

Recap On Aperture

Let’s recap on what I mentioned in the previous article, I mentioned…

Aperture refers to the diaphragm opening inside a lens. How wide the aperture is open is indicated by the F-number. The lower the number, the wider it is. The wider it is, more light goes through it.

Think of it at your eye lids again, but instead of being the duration of the eye lid being kept open, aperture is like how wide your eye lid is to open.

When you set the aperture value to the lowest value available (meaning widest aperture) then it would open the aperture blades as wide as it can. The aperture will close to the width as indicated by the setting in the camera. Increase the value and the aperture will reduce in opening size accordingly.

Still don’t get it? Look at the picture below. πŸ™‚ So as you can see, the opening of the aperture decrease as the value increase.

Knowing Aperture and How To Use It

The aperture available depends on the lens youÒ€ℒre using. The F-number will also be displayed on your cameraÒ€ℒs indicator, in the image below we see that the aperture is indicated – at f/2.5

Knowing Aperture and How To Use It

With the recap done, let’s move on to the more technical part.

F-number = Aperture?

In this article, I’ll make it really simple. the F-number indicate the aperture size. The F-stop on the other hand are the adjustable steps for the F-number.

Here’s what a Standard full-stop f-number scale

AV 1 2 3 4 5 6 7 8 9 10 11 12 13 14
f/# 1.4 2 2.8 4 5.6 8 11 16 22 32 45 64 90 128

For each raise of an aperture in 1 full-stop, amount of light that enters is reduced by half. So that basically tells you that for each full-stop you increase, your shutter speed needs to open twice as long. πŸ™‚

Here’s an image to illustrate to you how the aperture affects amount of light that enters through the lens.

Knowing Aperture and How To Use It

The shots were taken with the same shutter speed and ISO, with only the aperture being the variable. So as you can see, the photo on the left was taken with f/1.8 where the aperture was widest on that particular lens (Canon EF 50mm f1.8 II). The widest aperture resulted in too much light being captured, thus having the captured image over-exposed. On the right side, was taken with aperture set to f/8.0 but even though it’s not the smallest aperture available, it had already reduced the amount of light captured and resulted in an under-exposed photo.

To those of you who wants more understanding on the Aperture, how it works and how it is calculated,
A Tedious Explanation of the f/stop
F-number on Wikipedia

Aperture Affects Pictures

Besides affecting the amount of light that enter through the lens, the aperture also adds to the effect of the photos captured due to the change in how the light is captured.

The Bokeh

Those of you who hang around photography forums and articles would’ve heard it, if you’ve not heard about it then it’s OK because you’re bound to hear about it sooner or later.

Basically it’s a term to describe the blurred foreground and background in a picture. I like how the article at Wikipedia explained it.

Bokeh (derived from Japanese bokeaji ???, “blur”) is a photographic term referring to the appearance of out-of-focus areas in an image produced by a camera lens.[1] Different lens bokeh produces different aesthetic qualities in out-of-focus backgrounds, which are often used to reduce distractions and emphasize the primary subject.

So basically it’s wider the aperture, creamier the bokeh. Have a look at the image below that I’ve prepared to illustrate this point.

Knowing Aperture and How To Use It

Observe how the background looks diffused when the aperture is wide open and how it gets shaper as the aperture get smaller. The effect achieved for the bokeh (it affects both foreground and background) is also related to the Depth of Field which I’ll be talking about next.

The Depth of Field a.k.a. DOF

The depth of field (DOF) refers to the area in front and behind the focus point where the captured image is the sharpest. Now refer to the image below and see how aperture affects the DOF.

Knowing Aperture and How To Use It

The DOF extends 1/3 in front of the focus point and 2/3 behind the focus point. Meaning that if you have 1 feet of sharp area in front of the focus point, you’ll have 2 feet (twice as much) sharp areas behind the focus point.

Now refer to the next image, the DOF is reduced as the aperture is widen. (Remember – wider aperture, smaller f number)

Knowing Aperture and How To Use It

Understand better now? the DOF is reduced as the aperture is widen. It works vice versa as well, so the DOF is extended when aperture is reduced.

The DOF can also be reduced by using a lens of a longer range, as seen in the image below.

Knowing Aperture and How To Use It

Given the same aperture and focusing on the same subject of same distance, the longer lens – say 200mm, would have narrower DOF compared to a 100mm.

You could also experiment with the Depth of Field Calculator to understand better what I just mentioned.

Working the “bokeh” and “DOF”

There’s no formula on what to use for your bokeh or depth of field.

The idea is simple, you can’t be wrong as long as the picture looks nice. πŸ™‚ Sometimes the background looks rather distracting, even with some form of bokeh – then it’s clear that you should be hunting for a better background.

You might come by people who are huge fans of bokeh where any picture that has less ideal or no bokeh would be condemned – just ignore them! Great pictures are not judged by bokeh or depth of field but they can be manipulated to get great pictures! Remember that!

While bokeh makes the pictures look nice, setting too wide an aperture for your shot would result in the lack of depth of field, so your subjects end up being soft or blurred. A good example would be group photos, or where there are a bunch of friends around that you like to snap – I’m sure you’d want all their faces to be clear. πŸ™‚ So the next thing for you to remember is that while bokeh can be nice, you should always consider the depth of field.

These 2 factors can really make or break your pictures.


Aperture affects exposure time, Aperture affects bokeh and Aperture affects depth of field.

In the end, it’s all about knowing what type of photo are you taking and also what effect are you attempting to get out of the result.

We’ve come to the end of my lengthy and hopefully intuitive article.

I hope this article has inspired you to experiment more with aperture but before you leave, I have some examples I’d like to show which I hope it could give you a better understanding of the subject at hand.

Knowing Aperture and How To Use It

Let’s go through the picture clockwise, starting from the upper left picture

#1 – Aperture was used to blur the background to make sure the beauty of the peacock’s feathers do not become a distraction (I stood there for like 15 minutes to get that shot!), the depth of field was set to the bird in subject and also the food around the table.

#2 – Believe it or not, the background was just a lawn in my front yard, just an average lawn. Due to the settings used for this shot, the background turned out to be so creamy that it becomes just a shaded green background that helps emphasize the subject.

#3 – The focus was on the leaf, I had to make sure that the depth of field was sufficient to show the details of the leaf while blurring the textured background.

#4 – Wide aperture was used for this one. I wasn’t much concerned over the depth of field for this shot as the greater concern was capturing the moment. I need to freeze the motion, not just the swimmer but also the splashing water. The camera was set to use the widest aperture available on the lens, which was f/4.0. This ensure the maximum amount of light is available for the shot, thus I could use faster exposure to freeze the moment.

That’s all folks. πŸ™‚ Thank you for your time. I do hope that this article has brought much enlightenment to you.

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  1. Wow i love the #3 pic! I never knew you can take that kinda shot just changing the apeture! Imma go get my father’s canon 450D to do some experiment. Thanks goldfries!

  2. Oh great, still got more to learn about DSLR liao.. owned D400 but still didn’t know the secret inside the cam liao…

  3. nice. best bit is where u used your photos and showed how you got those effects. (:

  4. Author

    Thanks. Yes, I’m glad you guys appreciate the article. πŸ™‚ This probably one of my longest articles around.

  5. just to thank , you are doing a great job , I just have a nikon d300 and it is so hard to use it !!!!!! thanx for your help i hope to know more and more about digital slr !thanx again a

  6. Author

    The D300 is a really nice camera. πŸ˜€ Probably the best camera in its class.

  7. Hi there Brian,

    I just wanna know if the type of lens affect the bokeh – my friend told me that if i use 50mm lens i will receive bokeh effect quite easily. im currently using kitlens 55mm.

    so isn’t easier to just tell people – “go get your 50mm lens now people!” ?

    thanks! πŸ™‚

  8. Author

    Your friends aren’t telling you the full picture. Refer to the section “Aperture Affects Pictures >> The Bokeh”

    See, it’s not about 50mm or whatever lens, it’s about the aperture used. Use a 50mm at less-wide aperture like f/5.6 or higher f number and you won’t get as much bokeh in the first place. Lesser DOF, more bokeh you get.

    Your standard kit lens (whether Canon or not) has an aperture of f/3.5 on wide and f/5.6 at 55mm on tele. With f/5.6, the DOF is greater thus lesser bokeh.

    The 50mm they refer to (assuming it’s EF 50mm f/1.8) comes at aperture f/1.8 – and because of such wide aperture available, you have the option to use wide aperture to get better bokeh. πŸ™‚

  9. Good article la. Can you also explain on how to take a good picture using fisheye lens? Thanks in advance.

  10. Author

    You must first understand how a FISH-EYE lens works, then you’ll know how to use it. . There’s very limited use for it but when used correctly, the results are awesome!

  11. hi goldfries i hav canon EOS 30D…but no idea how to change de aperture n shutter speed…need help….can add my msn? [email protected]…10s

  12. Author

    alright! will do. (you could’ve added mine instead. πŸ˜› It’s on the contact page)

  13. wow, i like ur blog n enjoy reading it.
    learnt alot from here, thanks.

  14. Hi, goldfires, here would like to ask you something which regards to the picture number 4. You wide the aperture, but how about the shutter speed? Thanks

  15. this is something that really help persons with an interest in photo and taking pictures..^_^

  16. you explain things very well..make everything so simple and easy.. thanks for the effort.. you are truly gifted..

  17. been searching for bokeh and DOF explanation, and your’s the one that is easiest to understand. kudos!

  18. Great explanation with great pictures as guide…
    thanks for the tutorial

  19. This is a great article. i just used my photographer’s camera every time that I visit different areas and never thought how to use it properly or how my camera works well with me. This stuff is pretty handy, thanks for sharing this info.

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