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by Bart Arondson

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I want to take pictures of people from 5-20 feet away. I attend lots of group events and am free to walk around and snap photos.

I just purchased a Canon t3i and it comes with a 18-55mm kit lens. The aperture can go down to f/3.5 at the largest. However, I have a friend with a Canon 5D with 50mm f/1.8 lens and I noticed that his photos always come out nice when shooting up close. The background is always blurred.

I find that I get the shallowest depth of field when I zoom in (even if the aperture goes up), which is a problem. I don't want to have to back up from the subject to get a nice photo. If I really try, I can sometimes get the subject with a blurred background if I move in close (3ft) with a f/3.5.

So do I just need to learn how to use this lens, or would a getting a 50mm f/1.8 lens really help with taking pictures of people?

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See also photo.stackexchange.com/questions/2221 — although the question is vague, there are some good answers. –  mattdm May 4 '11 at 16:45
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I think its important here to note that it seems your definition of "better portrait photos" appears to really mean "shallower DoF". LOTS of other things can make portraits good and bad. –  rfusca May 4 '11 at 17:02
    
Getting up as close as 3 ft will also distort perspective (big nose). A 50 mm on APS-C (75 mm eq) is getting close to the preferred length for a portrait lense. –  Henk Holterman Oct 29 at 8:45

6 Answers 6

up vote 8 down vote accepted

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.

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Thanks for the link. However, after reading some of that I'm wondering if something like a +80mm f/1.8 would be better for my needs than a 55mm since I have a smaller sensor. –  Xeoncross May 4 '11 at 16:53
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That's a fine portrait lens, but you're going to have to be even further away from your subject, so you'll have to decide if that's a problem for you or not. (BTW, since your friend has the 50/1.8, maybe you can borrow it to try on your camera? You can assess the depth-of-field, the perspective and working distance, etc.) –  coneslayer May 4 '11 at 16:55
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doh, the info provided here is great, but I should just go borrow it! –  Xeoncross May 4 '11 at 16:57

Yes if you really want to blur the background get a fast (wide aperture lens). If you don't like having to back up to shoot at 55mm with the kit lens you should probably look at the Sigma 30 f/1.4

Otherwise the Canon 50 f/1.8 is great value.

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User 25034 wrote "You can but then you need your group to be close and the background as far as possible (like as shooting in a path between trees) " and then AJ Henderson suggested that answer was not very helpful or clear.

Part of your original question was "If I really try, I can sometimes get the subject with a blurred background if I move in close (3ft) with a f/3.5"

There are a few competing things here.

First - your friend's lens has a maximum aperture of 1.8, vs your best aperture of 3.5. His larger aperture will result in a shallower depth of field, all else being equal. So you're already one notch down.

Second, you can only acheive 3.5 at the wide end of your lens - ie. 18mm - but this focal length will distort faces significantly. As others have mentioned, 70mm, 80mm and up over 100mm produce portraits that appear more realistic in facial proportions than using a wide angle. Therefore you will want to use the 55mm end of your lens as much as possible - however one of your comments suggests the aperture gets even smaller at that end of your lens - now you're two notches down on your friend's lens.

Third, depth of field is not only dependent on aperture; it is also dependent on the distance between the camera and the subject - the focusing distance. Take an example: If you got really close to the lined pages of a (paper) notebook, and took your shot at f3.5, you might expect 1 or 2 lines to be sharply in focus and the rest of the page pleasantly blurred (assuming you're looking along a page). These lines might be 1cm apart. Now imagine the same exercise in a carpark, looking down a row of cars. You might find 1 whole car is in focus. One car is definitely wider than 1cm, but your camera settings have not changed. The depth of field is dependent on the distance from you to your subject.

Therefore if you get closer to your subject, then your depth of field will reduce - but you want to avoid reducing your focal length below 55mm too, in order to avoid distortion in facial proportions. You're a little stuck here but read point four.

Fourth, and this is where the comment by User 25034 comes into play, imagine your subject (say a face) is really close to a wall (say the person is leaning against the wall) - even if you reduce your depth of field so that only the face is in focus, because the face is so close to the wall, the wall will still be highly recogniseable. However if you imagine the subject 5 steps away from the wall, now the face is crisp but the wall is so far away that it is really out of focus. Therefore while taking your shot, you could look for angles whereby the background is further away from your subject. This might mean a profile shot will give you a more blurred background - if that is the angle that results in the background being furthest away from your subject as is possible.

Note that regardless of the distance to the background, nothing changes in your aperture or in the distance between you and your subject, or in your focal length - hence this part of the photo (the face) will retain the same proportions / viewing angle, and the same sharpness and focus. Although your subject is not actually closer to you, it is relatively closer to you (compared to the wall) than when the person was leaning against the wall.

So to say in your question "if I move in close", it might be more helpful to think of it as "if I move in relatively close, compared to the background" - then yes, your photos will improve as you desire. Just remember, your kit is still starting two notches down compared to your friend's.

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Large, wide open aperture (smaller f number) will result in blurred background. You need to focus more carefully on the eyes. But a 50mm in a full-frame camera is pretty short for making head and shoulders portraits. An 85mm or longer would yield an even nicer portrait in your friend's camera because it will allow him to get back a bit. This longer perspective will keep noses from getting large, etc. I think the 55mm end of your zoom is likely to give a nicer portrait perspective in your camera than your friend's 50mm on his larger sensor. But it will not have as shallow a depth-of-field. And his lens on your camera should result in a really nice portrait. (They probably make an adapter which might be a cheap way for you to try before you buy.)

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So do I just need to learn how to use this lens, or would a getting a 50mm f/1.8 lens really help with taking pictures of people?

Yes. Both.

As others have already explained, a lens with a larger aperture will definitely help. It may be more than you bargained for, though! Even on a crop sensor camera, at f/1.8 and a distance of 1 meter, the depth of field is only 3cm. That means you might get the eyes in focus, but the nose out of focus. Or just one eye in focus. Or the nose but not the eyes in focus. Shallow DOF is a cool effect but it makes it easy to take a lot of not so good photos, so you have to be careful. At f/5.6, on the other hand, you get 8cm DOF, which makes it a lot more likely that you'll get the entire face in focus.

Increasing the distance to the subject increases the depth of field, and that happens faster with smaller apertures. In other words, f/1.8 lets you shoot from twice the distance as f/5.6 while keeping the same DOF. Knowing that, you can consider your options:

  • Get a lens with a larger aperture.

  • Use the lens you have with the smaller aperture, but get closer to your subjects.

  • Use the lens you have at the distance you're used to, but position your subjects farther from background objects (or choose subjects and shooting positions such that background objects are farther away).

Also, remember that a fast prime lens has other pros and cons to consider:

  • pro: Prime lenses tend to be sharper than zoom lenses.

  • pro: A larger aperture lets in more light, which means that you can use a faster shutter speed, or lower ISO, or both.

  • pro: A lens like the EF 50mm f/1.8 is small and light, even compared to the EF-S 18-55mm.

  • con: The 50mm f/1.8 doesn't have image stabilization. (Alternately, pro: the 50mm f/1.8 doesn't need image stabilization.)

  • con: You can't zoom out with the 50mm f/1.8, except with your feet, and although that can be effective it's really not the same thing.

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You can but then you need your group to be close and the background as far as possible (like as shooting in a path between trees)

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Why do you suggest this? –  mattdm Dec 31 '13 at 21:28
    
While I think you are saying that you could use the existing lens to accomplish the goal by doing what you suggest, however the way your answer is phrased doesn't really make sense to someone who doesn't already know that. The question was asking either "will a lens with low aperture value give better portraits?" or "do I just need to learn how to use the lens?" Without further expanding that it is possible, but harder and that he needs to take a photo like you describe to get a background blur, it isn't very easy to follow. –  AJ Henderson Dec 31 '13 at 23:05

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