Aperture priority mode

learn to control your aperture

In this tutorial we are going to learn what aperture priority mode is, when to use and and why, see few examples and do an easy exercise in order to learn to control this setting

Aperture priority mode – definition

Aperture is one of the 3 settings of the exposure triangle along shutter speed and ISO. AS already covered in previous lessons a proper exposure is the combination of the 3 elements.

Aperture priority mode is the setting when we control the APERTURE size and let the camera choose the time of exposure – or shuter speed and ISO = sensitivity of the sensor. 

In this mode we tell the camera how big the whole of the lens is, and how much light to allow inside. The camera will assess the lighting level and adjust the time and ISO accordingly. ISO can be also locked manually and the camera will be left with only one more choice: the shutter speed. In normal lighting situations, the camera will make a the best selection, however if there is too much light or not enough, the image will become overexposed or underexposed as the limitations are reached.

Applicability of the aperture priority mode

The question is when do we want to use this mode. The size of the whole usually impacts the depth of field, how deep in the image is the focus, how deep the image is sharp. The general rule is: the wider the aperture – translated in the diameter of the lens hole, the more shallow is the depth of field. For smaller apertures, the depth of field is larger, so we can have more depth of the image in focus.

we have already covered the F stop/aperture terminology in the other tutorials 

So the general rule for using the aperture priority is when we need to control the depth of field.

If we want to have an image like the one above with a sharp focus point and the rest is blurry, then the aperture priority mode is the right choice. The larger the aperture, the more blurry are the front and the back.

Priority mode setting – options

To get into priority mode you need to dial the Av setting on your camera and select the aperture. Depending on your camera, the symbols might be different, but for any DLSR camera, the mode should not be a problem. You will have the choices limited by your lens. The aperture normal sizes are F1.2, F2.8, F3.5, F4, F5.6,F8, F9, F12, F13, F16, F19,F22. Each lens is different and will limit the aperture.

Quick exercise: grab your camera and note done  your options to understand your limitations. Does you lens start with F2.8 , F3.5 or F4? where doe s it finish?

The smaller the aperture, the less chance to get the blurry images people love.

Important note

Just because we are making the theory of the depth of field, that does not mean you are going to get the blurry background as you probably want

The blurry background is the size of the depth of field and it is given by the lens selection first, and aperture size second. we can have 2 different lenses with the same aperture but the depth of field is different. Best example as above images where the ring is taken with a macro lens F2.8 and the portrait is taken with the telephoto same F2.8. One depth of field is just few mm, and the other few tens of centimeters. Same Fstop 2.8 but 2 different lens.

I was confused myself about this issue at the beginning and i was trying to get the narrow depth of field with my first lens and got angry when everyone was saying that I do not have the skill to get it and I should set up the aperture to the maximum. I was doing that and never got the result until I borrowed my first telephoto lens and the blurry background was achieved without any effort.

IT IS MORE IMPORTANT TO HAVE TH RIGHT LENS RATHER THAN RELYING ON APERTURE PRIORITY TO ACHIEVED THE DESIRED DEPTH OF FIELD

Exercise:

Grab you camera and test all the aperture settings in increments in a similar arrangements as per below so you can understand your camera and lens behaviour.

Our test starts with Aperture priority mode Av – ISO on automatic and the camera will select the shutter speed

F3.5

F4

F4.5

F5.6

F6.7

F8

F9.5

F11

F13

F16

F19

F22

As you can not on the above the smallest aperture will give you the first and the last glass clear in focus. Just to mention, the focus wsa manually set up to the glass in the middle. Comparing to the first image taken with F2.8 as the largest aperture, the first and the last glass are blurry , out of focus

Conclusion

The Aperture priority mode will allow you to control the depth of field. Each Aperture will increase or decrease the depth where objects are in focus.

Just few notes:

- different lenses will give you different results

- different lenses will have different F stops.

- distance to the subject will give you different results

So, just to fix this topic, you need to test your camera few times and you will understand the limitations of your own camera, and which aperture settings give you what depth of field.

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