Snap!torial: Aperture

January 13, 2014  •  Leave a Comment

Aperture  refers to the hole the light travels through when the shutter releases, specifically the size of the hole.   Logistically, when you snap a photo, the instant you push the shutter button, the shutter fires, momentarily allowing light to travel through the aperture to expose the photo.  You need the perfect amount of light allowed in to correctly expose a photo.  We’ll look into Shutter Speed and how the combination of shutter speed + aperture creates the perfect exposure in later Snap!torials. 

For now, let’s concentrate on Aperture.  When the hole is bigger, you’re allowing in more light in the instant the shutter fires.  When it’s smaller, less light.  Why does this matter?  Well, the size of the hole (ie the aperture) effects the depth of field (ie the blurriness or sharpness of the things in a photo that aren’t in focus… you know the super blurred background effect…) and the plane of focus. 

In portrait photography, the trend-du-jour is creating super blurred backgrounds.  I’m loving this trend and I hope it stays forever and ever and ever…. For one reason, the stark contrast between blurred background and sharp subject is incredibly pleasing to the eye.  Without too much effort, you draw the eye to the subject.  This goes a long way in forgiving a less-than-perfect composition.  Also, I find that “soft” images (where you have the focus off just a smidge) can sometimes be salvaged.  Your eye won’t notice that the subject isn’t perfectly sharp, since by comparison to the background, it’s super sharp.  To clarify, in no way am I saying this is an excuse for poor photography.   Just that it’s nice for a current trend to be somewhat forgiving.  

Aperture is notated as an F Stop, “f/”.  The naming convention for  F stops is a bit counter-intuitive in that the smaller your F stop number, the wider the hole… and the wider the hole, the more blurry the background is.  In this image comparison, notice the difference in the background blur in each picture- it's easy to see if you compare "argoflex" on the camera on the far right.  Note also that for each change in f stop, I had to make an equal and opposite change to the shutter speed.  Makes sense if you think about it...  when you make the hole smaller, you need to keep the shutter open longer to get the correct exposure.  

You have control over Aperture when shooting in A (Aperture priority) or M (Manual) modes on a DSLR by toggling to the desired aperture.  Consult your user manual for how to do this with your specific camera model.  The aperture is a function of your LENS, not your BODY, even though you control it via the camera body.   You will notice around the edge of your lens a notation starting with f/, example “f/1.8” means this lens goes down to 1.8 aperture.  The high end of a range isn’t notated.  For lenses that zoom, you might see “f/3.2-4.8.” That means that at one end of the zoom, your lowest aperture is 3.2, but while zoomed in, your lowest aperture is 4.8.  Unfortunately, the typical way things go is the lower the aperture, the more expensive the lens.  

To create the blurred background look, toggle your aperture down to the lower end the lens allows, being aware that if you’re in Manual mode, you’ll need to adjust the shutter speed to accommodate this change.  Also, create distance between your subject and their background.  The more distance between the plane of focus and the background behind them, the greater your blur effect will be.  It helps when posing people with a wall/fence/fireplace/etc. as the background to have them step away from the background.  I usually try to get them as far away as possible to still keep the composition of the image pleasing.  Be careful in going too low with your aperture.  It’s fun to play with and it’s easy to get in the mindset that if a little is good, then a lot is better, and then just dial that baby down to the lowest aperture your lens allows.  Well, the problem with that is that the lower your aperture, the skinnier the plane of focus…  So, you might end up with a nose in focus and the eyes blurry because you’ve gone too low with your aperture creating too little depth of field.  Especially when there are multiple subjects in your photo, it’s hard to get them all in focus at super low apertures. 

In contrast, for landscape photography, you want EVERYTHING to be in focus.  To achieve this, dial up the aperture.  This isn’t my strong suit, so I don’t want to give bad advice here.  Play around with it to see how high you want to go.   This is also how you would achieve those silly photos where people are pushing the Leaning Tower of Pisa or Washington Monument over.  With a high aperture, everything is in focus, and you can’t distinguish any distance between the subject and the background. 

To sum it all up:

Low F/stop = wide hole = lots of light = low depth of field = blurry background

High F/Stop = small hole = little light = high depth of field = sharp/ focused background

Aperture + Shutter Speed = Exposure

Happy shooting!


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