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Focus problems with pictures of multiple people

edited March 2015 Posted in » Nikon D3100 Forum
When taking family portraits or even photos of 2 or more people (honestly, occasionally even with a single person), my photos are not clear. I'm doing a family wedding in July, and I'm nervous about wedding party and family photos. I have a 50mm 1.8G, 35mm 1.8G, and the kit lenses. Thank you!

Comments

  • edited April 2015
    With multiple people you will have to go for greater depth of field than might be ideal for a single portrait. You don't want to blur the background if part of the background is more people. You'll get more depth of field with a smaller aperture (larger F number), a wider lens, and greater distance from the subject.

    Make sure too that your focus is hitting the right people. Auto area focus may not choose the right subject. Try a single point focus mode.

    Depth of field is always greater behind your main subject than in front. The actual distances are complex and variable, but a useful sort of rule is to try to focus a bit closer than the center of your range. At normal distances, divide your depth of field into thirds, and set your focus point at about the first third. It takes some trial and error, but for an example, imagine that your subjects are scattered between 10 and 25 feet away and that you've found a setting that gives you the required depth of field. Your best focal point will be, not halfway between 10 and 25 (17.5), but at about 15.

    Since distance and wider focal length both favor depth of field, experiment with ideal placement relative to the people you're shooting. When you're doing groups, you may even find it necessary to stand back and crop later in post processing. Any one of the lenses you have should be able to get sharp pictures of people.

    When you're doing a single person, make sure you have single point focusing, and aim for the eyes. If you're going more for information than mood, use a higher f stop than 1.8 so as to give you more latitude in focusing and insure that the whole face is sharp.
  • edited April 2015
    Thank you for answering! I'm very new to photography. Do most people learn this stuff from trial and error? I'm going to do some research on the depth of field stuff. For some reason that is very confusing to me, of course it doesn't take much, lol! By "wider lens" do you mean for example using the 50mm 1.8G? Then would I use an aperture of say 20 while standing farther away?
  • edited May 2015
    In "lens-speak" wider means a shorter focal length, which gives you a wider angle view. It can be confusing since one also speaks of using a lens stopped down or wide open. Different wides!

    The word "fast" is another that can confuse. A fast lens is one with a wide aperture that lets lots of light in. A f/1.8 lens is fast, a f/5.6 lens is slow. A fast ISO is a high one that lets a lot of light in. ISO 3200 is fast, 100 is slow. A fast shutter speed is the opposite, since the faster the shutter operates, the less light gets in. 1/4000 is fast, 1/4 is slow!

    For reasons too complicated to explain, F stop numbers are the reverse of all the other numbers. The smallest number is the largest aperture.

    Three things determine depth of field:

    1. Aperture. The largest aperture = the shallowest DOF. If you have a 50mm f/1.8 lens, it will be very shallow at f/1.8, and much deeper at f/16. This is why people shooting portraits like those fast (in lens speak fast means big aperture) primes. Shallow depth of field isolates a subject and blurs background and foreground. It also makes focusing harder, though. The rules are different between a single face portrait and a scattered group.

    2. Distance. The closer a subject is, the shallower the depth of field will be with the same lens and the same aperture. This is how fixed focus box cameras can work. They are set to focus at a fair distance, with a small aperture, and as a result, their depth of field is very great. If you set your normal lens at f/8 and focus at about 20 feet away, nearly everything will be sharp from about 10 feet to infinity. If you take the same lens and go to near-macro closeness, almost nothing but what you're focused on will be sharp.

    3. Focal length. The shorter the focal length, the more the depth of field. A 35mm lens will have more depth of field than a 50mm. If you frame a shot the same with both lenses, some of that difference will be lost to distance, but not all. The longer lens will still have shallower depth of field.

    So for group shots, you will want to favor a fairly short focal length, and an aperture small enough that everyone you want sharp is within its depth of field. Be a little cautious with very wide angle focal lengths, because the perspective can be unkind to faces. You know those funny greeting card shots of a dog with a disproportionately huge nose, and such? That's what you get from extreme wide angle extremely close! You won't get that by mistake, but a wide angle will make faces look different. 35mm is normal perspective in the DX camera format, and you're probably best off not going any wider than about 24 for people if possible.

    As for how you learn this stuff, yes a lot of trial and error, but also some books and what not help. These days there's a lot of good information on the web if you look around. Of course getting older helps, but we pretend otherwise.


  • edited May 2015
    I would love to get better family shots. I have been using my 50mm f/1.8 lens. I just downloaded the cheat cards and hope they help. Any advice on what settings I should set my camera to when doing group shots? I've noticed that the focus area remains really small, so whoever is sitting closer to the ground or not smack in the middle is blurred. I want to learn and get better but I do get confused with all the different phrases and numbers.
  • edited May 2015
    The simple answer here is that you need more depth of field, and for that you need to stop down the lens more (higher f stop number). The wide open setting for portraits is ideal for a single subject, whom you want to stand out against a background and foreground that are blurred. But for group shots the same setting will treat other people as part of the background and blur them too. You will not see this in the viewfinder, which always looks through the lens wide open. The set aperture takes effect only when you actually press the button. You'll have to take a picture and look at the results.

    Since depth of field is slightly better behind the subject than in front (rough average about 2/3 to 1/3), try focusing a bit closer than the middle of a crowd to get the most in focus.

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