Will a faster lens help me get blurred backgrounds for portraits on a Canon T3i?

Asked 5/4/2011

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I shoot people at parties and events from about 5–20 feet away with a Canon T3i and the 18–55mm kit lens. I’ve noticed that a friend’s Canon 5D with a 50mm f/1.8 gives much blurrier backgrounds in close portraits. With my kit lens, I get the shallowest depth of field when I zoom in, but then I have to stand farther back than I’d like. If I move in very close at f/3.5, I can sometimes blur the background, but not consistently. Would a 50mm f/1.8 really help on my camera, or do I mainly need better technique?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

15y ago

2 Answers

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Yes, a lens with a larger aperture (numerically smaller f/number) will produce a shallower depth-of-field, and a more blurred background. However, there's another factor working in the 5D's favor: It has a "full frame" sensor, the same size as 35mm film, while your camera has a smaller "APS-C" sensor. The larger sensor results in a shallower depth of field, for the same composition and aperture setting. See Matt Grum's comparison in this thread. So the 50/1.8 will be an improvement, but may not reach what you're seeing from your friend's 5D.

Also, you said you don't like zooming in with your 18-55 lens, because you prefer to work closer. Keep in mind that a 50mm lens will be similar to the long end of your zoom, so it may not mesh with your preferences.

Originally by user2138. Source · Licensed CC BY-SA 4.0

user2138

15y ago

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AI Answer

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Yes—a faster lens will help. A lens with a wider maximum aperture, such as f/1.8 instead of f/3.5, can produce a shallower depth of field and stronger background blur.

But there are two other factors too:

  • Your friend’s 5D is full-frame, which gives shallower depth of field than your T3i’s APS-C sensor for the same framing and aperture.
  • Longer focal lengths also blur backgrounds more, which is why your kit lens looks best at the zoomed-in end.

So a 50mm f/1.8 on your T3i should improve subject isolation, but it may not exactly match what you see from a 5D with the same lens.

Also note that 50mm on a T3i will behave like a short telephoto, similar to the long end of your zoom, so you may still need to stand back more than you prefer. If you want a wider view with a large aperture for people shots, a fast lens around 30mm may suit you better.

Technique still matters: keep the subject farther from the background, and avoid very wide focal lengths for close portraits because they can distort faces.

UniqueBot

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15y ago

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