Aperture & Portrait Question

[TraceyHill3]

If I'm doing a portrait session and I want to take full-body shots, how do I keep the whole body in focus while blurring the background? I thought if I had the aperture set on something like f4 not all of the body would be in focus.

[RichardTaylor]

It depends on how far away your subject is, and how far away your background is as well as the aperture. If the subject size is kept constant in the viewfinder the focal length doesn't matter all that much, however the appearance of the background will change.

Try plugging some numbers in to this calculator to see hoe much DOF you have to work with.

Online Depth of Field Calculator


Here is a recent example of mine shot at F5 where the background is out of focus however the subject is sharp.
A larger version is on my Flickr stream




Camera Canon EOS 40D
Exposure 0.017 sec (1/60)
Aperture f/5.0
Focal Length 100 mm
ISO Speed 100
Exposure Bias 0 EV
Flash Off, Did not fire

[SusanH1970]

Agreed with Richard. You can shoot a full body portrait wide open, actually - it gets tricky when there are several people on different planes. These folks were more or less on the same plane, so they're all in focus at f/2.2.

The DOF calculator is a fantastic tool!


Camera Canon EOS Digital Rebel XSi
Exposure 0.001 sec (1/1000)
Aperture f/2.2
Focal Length 50 mm
ISO Speed 100

ETA: Richard, that's a great shot, it made me smile!

[RichardTaylor]

Thanks Susan, it was at the end of a sunrise shoot.That guy is an excellent photographer.

[zona5101]

you can get a pretty decent free DOF calculator for your iphone/itouch...
has a grahical display of the range of focus... you dial in the fstop, focal length and subject distance on a spin wheel and it will display the near and far focus points, show the total dof distance as well as list the hyperfocal distance

myPhotoDOF
thru itunes store

[TraceyHill3]

Thank you all for the reply! I loved both examples. I'm going to check out a DOF calculator for my itouch, but I'll bookmark the link you sent above.