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Photography Tips - Using Aperture Priority

 25th Nov 2010

Aperture PriorityWe’ve had lots of requests on our ‘Tell us what you want’ page for a film about how and when to use aperture priority (also called ‘AV’ for Aperture Value).  So we’ll certainly be making a film about it for our photography videos section soon.

When you set aperture priority mode (or AV) you’re telling the camera that the aperture you’ve set is the most important thing, you’ve chosen it for a reason (more on that in a moment) and that it must use it.

So the camera will go and find you a shutter speed to work with your chosen aperture that will get you the correct exposure for the shot you’re taking. 

When shooting in aperture priority you’re in control of apertures ­- and the camera is in control of shutter speeds.

Aperture priority is a semi automatic mode which gives some of the control to you, whilst the camera works out the tricky bit (the exposure) for you. It does this by selecting an appropriate shutter speed to let in enough light for an image to be recorded by the camera’s sensor.

Unfortunately there is no ‘standard’ shutter speed. Exposure is dependent on how much light is falling on your subject, so when there’s not much light about like on a dull day, your camera will choose a slow speed which could be anywhere from several seconds up to maybe a 60th of a second. 

And when there’s lots of it such as in strong sunshine, it’ll set a fast speed which might be something like a 1000th or more.

This happens regardless of subject. Set your camera up in aperture priority on a tripod and take a picture of your garden on a bright day and your camera will use a fast speed. Leave your camera with the shot set up and take the exact same picture when a cloud covers the sun and it’ll set a slower one.

aperture priorityThat’s actually all there is to it!

But which aperture to choose?
Aperture priority is my favourite mode and I use it 99% of the time because aperture size does more than just manage how much light gets in ­ it's also the main depth of field control too, so aperture priority lets you be creative!

As you change your aperture or ‘F’ numbers (also known as ‘F’ Stops) you in-crease and de-crease how much front to back sharpness you have in your picture.

If for example you have two people, flowers or even a building and a leaf one in front of the other, then using aperture priority you choose a wide aperture; the thing you focus on will be sharp and the other will be soft.

Just by shifting your point of focus you choose which!

Now - if you’re using an auto area focus mode there’s no knowing what the camera will choose to focus on - so set up your auto focus to use single spot mode for this kind of shot.

aperture priorityNow sadly I have to tell you the person who invented ‘F’ numbers needs a good talking to because they’re back to front!

Here’s how it works.

Wide apertures first ...

  • Wide apertures are low numbers like 2.8 or 4 or 5.
  • They give you a shallow (small) depth of field - good for fuzzy backgrounds or foregrounds
  • Careful focusing is very important to make sure the bit you want sharp is sharp
  • Because they’re ‘wide’ more light gets in so your camera in aperture priority will set a faster shutter speed

Small apertures ...

  • Small apertures are high numbers like 16 or 22 or more
  • They give you a deep (big) depth of field ­- good for landscapes and scenery
  • Focusing not quite so critical ­- rule of thumb is go for a mid point
  • Because they’re small less light gets in - so your camera in aperture priority will set slower shutter speeds. Use a tripod to avoid blurry pictures caused by camera shake.

When to use aperture priority
Aperture priority is very versatile so you could use it almost all the time. If you need a slower shutter speed - just set a smaller aperture and the resulting loss of light will force the camera to set a slow one.

The opposite applies too. Set a wide aperture and more light gets in through the lens so the camera sets a faster speed to compensate.

I use aperture priority for

  • Landscapes
  • Macro
  • Portraits
  • Weddings
  • Motor sport

About the only thing I wouldn’t use aperture priority for is Flash photography which I prefer to do manually or in a Programme mode -­ but that’s another story.

I hope this photography tip has helped you get your head around aperture priority. Well be making an aperture priority video and adding it to the photography videos section very soon.

mike browneThank you to everyone who’s filled in our Tell Us What You Want page -­ you’re making a difference.

If you’d like to know more about all things photography please check out our Photography Videos section ­ we’re adding new content every month. And our downloadable Beginners Photography Course, Wedding Photography Course and One to One courses are still as popular as ever.

Good luck and happy shooting till next time ....


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