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Sweet spots – Why your f/1.8 isn’t so great at f/1.8

Sweet spots - Why your f/1.8 isn't so great at f/1.8This may hit some beginners like a ton of bricks so brace yourself for a mild disappointment here: your lens isn’t wonderful at all f/stops. Yup. A Canon nifty fifty which opens to f/1.8 isn’t at its best when it’s wide open. And by ‘best’, I mean when a lens it at its sharpest. You see, there’s something known as a lens’ ‘sweet spot’ which is the aperture at which it’s at the sharpest and sometimes will even offer other things like better clarity.

It’s hard to give a blanket statement about the exact sweet spot for each lens because when you look up the chatter on the internet, there are such varying statements about, say, the sweet spot for the aforementioned Canon 50mm f/1.8. Some say it’s f/2.2 while others claim that the sweet spot is f/4. A good rule of thumb is that a lens starts moving more towards perfection about two stops above its maximum aperture. So where an f/1.8 can open all the way to f/1.8, you don’t actually want to shoot at f/1.8 if you want optimal sharpness and clarity. Try moving up a couple stops to f/2.2 or f/2.8 and compare the results you achieve.

While you can get info on the internet about your favorite lens’ sweet spot, the best thing you can do is set up a scenario and take a shot at all different apertures. You can do this by setting your camera on AV (or A on a Nikon) which is aperture priority mode. This means you will be able to change only the aperture and the camera will take care of all the other settings for you while you carry out your test. I would recommend using a tripod to eliminate factors that can alter sharpness like camera shake. After taking the photos, look at the images at 100% in your computer and you’ll notice some are sharper than others. Note the apertures used for those shots and you’ll know where to stay when shooting with that lens from then on.

I can hear you thinking: so I just spent over $1k on an f/1.2 and I can’t actually use my lens at f/1.2? I feel your pain – I’ve already gone through that grieving process myself! When talking about 50mm lenses, you could say that…

  • the max aperture on a f/1.8 is f/2.2
  • while the max aperture on an f/1.4 is f/1.8
  • and on a f/1.2, it’s going to be f/1.6

So you see, you’re still getting wider apertures, just not as wide as you may have first thought. But don’t let this sweet-spot-business discourage you from experimenting with and employing all sorts of wonderful wide-open apertures. It’s just important to understand how your gear works and how to get the best out of it.

So how about you – please comment below and share with us your sweet spots!

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Elizabeth Halford
Elizabeth Halford

is a photographer and advertising creative producer in Orlando, FL. She wrote her first article for dPS in 2010. Her most popular one racked up over 100k shares!

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