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Diaphragm opening

How to open the diaphragm on a camera? 


Tutorial to learn how to adjust the opening of the diaphragm on a camera 


What is the purpose of opening the diaphragm on a camera? 

To be able to use your camera correctly you will need to master the amount of light that enters it in order to have your photos correctly exposed (neither too bright, nor too dark) and sharp

As we have seen in other formations, this depends on three elements: 

  • Firstly, shutter speed
  • Then ISO sensitivity
  • Finally the opening of the diaphragm which we will discuss now!

Before the light hits the electronic sensor of your camera, the light will pass into your lens through a diaphragm. 

The diaphragm is a mechanism which can be adjusted by opening or closing it to bring a certain amount of light into the body of the camera. This is why it is called opening the diaphragm


Diaphragm Opening camera

Open the diaphragm = more light ==================> Close the diaphragm = less light 



The opening is equal to the focal length of the lens divided by its diameter. 

It is a square root progression 2 (√(2) =1.414), it gives the following values: f/1.4 – f/2 – f/2.8 – f/4 – f/5.6 – f/8 – f/11 – f/16 – f/22, etc. 



Adjust the opening of the diaphragm on a camera 

Between two values of the scale the diaphragm will let in twice as much light – when you increase (or decrease) by one notch, you double (or half) the amount of light. 


For example: 

  • if you go from f/5.6 to f/4 you will have TWICE the light
  • if you go from f/1.4 to f/2 you will have HALF the light!


Do not confuse

The lower the number, the wider the opening, the more light you get. 

As you can see from the diagram, f/1.4 is the largest possible opening, so it lets in A LOT of light, f/22 is a very small opening which lets in very little light. 


Photo edited in Lightroom. [Click here to learn how to use Lightroom.] 



Photo lens aperture 

To know the maximal opening of the diaphragm of your lens just look at it – the figure is written above on it (for example f/2.8). And yes, not all lenses have the same maximal opening. In other words this is why some cost €100 and others €3,000. The more prominent (brighter) the opening of the lens, the more expensive it will be. (And if the focal length is long, the price will be even higher.) 


Entry-level lenses usually have a maximal opening of f/5.6 while on high-end lenses the maximal opening will be f/1.4


We can also have several maximal openings on the same lens. Zooms, for example, can have variable maximal openings depending on the focal length position. 


Take for example the Nikon 18-300 F/3.5-5.6 lens. 


When the lens is in the 18mm position, its maximal opening is f/3.5, whereas if it is in the 300mm position, its maximal opening will be f/5.6. 

Tutorial How to choose which camera lens to buy ?


  • Low number (f/1.4) = large opening = brighter
  • High number (f/22) = small opening = darker

The opening of the diaphragm has an important effect on the depth of field, so to learn this I suggest that you read The depth of field tutorial. 


Mastering the opening of the diaphragm will allow you to produce incredible effects on your photos. With shutter speed and ISO sensitivity these are the three most important settings for getting good exposure. Once you understand these three parameters, you’ll have no more blurry photos, and feel the pleasure of photography



Give us your opinion, and share your experience in the comments. 

And if you think that this article helped you, share it! 

Have a nice photoshoot! 


Lightroom and Photoshop Tutorials 

February 17, 2020

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