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Multi-focus

mgmmgm
edited September 2015 Posted in » Nikon D5100 Forum
I am struggling taking photos with multiple subjects and keeping them all in focus. It seems like my camera can only focus on one face/subject at a time. Is there a way to focus on multiple faces in one shot? I did a shoot with my two children this morning - good light, indoors. I used the following settings: ISO 200 to 320, AF-S, matrix metering, and I tried switching back and forth between Single Point & Auto Area AF. I used anywhere from f/1.8 to 2.5 for my aperture. Any ideas on why only one of the two subjects were in focus in any given shot? Is there a way I can add one of the photos as an example?

Also, I will be doing a photoshoot for a group of 8 this month, outdoors. I have a 50mm lens I will be using. Any tips for getting all 8 people in focus without loosing the sharpness and good light?

THANK YOU in advance!

Comments

  • edited September 2015
    Depth of field depends on three things: aperture, distance and focal length of lens. The one you can vary with a given prime lens is aperture. You simply cannot get enough depth of field when the lens is wide open. The "bokeh" or blur of out of focus areas, which is so desirable in portraits with such a lens, is your enemy in group shots. You must close the lens down. If your people are not moving around, you can keep your shutter speed down in the 1/80 range or so pretty safely (depending greatly on your own ability to hand hold). People in general are less noticeably affected by high ISO noise, so crank up the ISO as needed, or use Auto ISO.

    If you have the kit zoom lens, it will likely give you more depth of field, both because it is slower (smaller aperture) and because you can use it at a shorter focal length. To avoid distorting faces, you probably don't want to go much wider than 28 millimeters or so, but doing so will greatly increase your DOF.


    Although some of the DOF advantage of a short focal length is cancelled by having to move closer, it is still a net gain.

    You'll probably get the best combination of depth of field and lens sharpness at something around f/8 or f/11. At a reasonable distance, that should be enough. Diffraction (softening of the whole image) will begin to set in as you approach f/16. It's still better often to have a little loss to diffraction if you need the depth, but you're better off if you can avoid it.

    Depth of field is always better behind the focal point than in front of it, so when deciding where to focus, err on the close side. As a sort of loose rule, whatever your focal point, the DOF will be about 1/3 in front, and 2/3 in back.

    Here's a link into which you can plug your camera and lens focal length and find out what your DOF will be. Note that at f/2, and ten feet, you only have a foot of depth of field! At f/8 and the same distance, you have four feet. At f/11 and 20 feet, you have 30.

    http://www.dofmaster.com/doftable.html
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