Is there a preferred Depth Of Field for portraiture?

I've noticed with the 50mm f/1.8 lens that if you want great depth of field you really have to stop down quite a bit, as you can still produce blurred backgrounds at 5.6 or smaller. Sometimes if I'm not careful I get good bokeh when I don't want it. I was wondering about doing portraits with this lens. How much depth of field do you want? Do you want enough to cover the range from front to back of your subject and not beyond that? How do you determine where correct DOF is for headshots and waist up shots?

Hey, Robert, this may help you out: DOF

I like to have just the subject in focus.

Rhinotherunt wrote in post #2212295
Hey, Robert, this may help you out: DOF

I like to have just the subject in focus.

Excellent. You know, I have that as a link and have looked at it but I never thought to just use it for this question. Now that I look at the table I can see exactly why f/2.8 or better have been recommended, aside from the fact that f/2.8 or better is considered the sweeter part of the lens. It looks like if the lens is open any wider the DOF goes down to the point where someones face might be in focus but their ear might not be in focus. The light went on!

That leads me to another related question. Now assuming that I have my numbers and my DOF for having the camera 6 feet from the subject and having a DOF of a little over 12 inches, how do I think bring in a background that may have a pattern that I want to be blurred. Is the amount of blur then controlled by the distance between subject and background? so the closer the subject is to background the closer it is to being with the DOF range and further away puts it way further out of that range? Do I have it right?

The closer to the lens the subject is the more the background will blur out. Farther from the lens the subject is the less the background will blur. Also depends on the overall distances and mm the lens is.

Yes but what I am saying is this.

If I want to be 6 feet in front of my subject, so as not to be too close, and I am determining a DOF (and aperture value) based on that, then that istance is set. So how do I now control background blur? can't I? Increasing subject to background distance doesn't have any effect on this? I thought it did.

Rhinotherunt wrote in post #2212295
Hey, Robert, this may help you out: DOF

I like to have just the subject in focus.

Having stuff in focus is overrated. That's why you need to use manual focus and make sure to always set it to the opposite distance (i.e. if subject is 1.4 feet away, put the distance to infinity and fire away.)

JaGWiRE wrote in post #2212409
Having stuff in focus is overrated. That's why you need to use manual focus and make sure to always set it to the opposite distance (i.e. if subject is 1.4 feet away, put the distance to infinity and fire away.)

I don't understand what you mean. Can you clarify?

TMR Design wrote in post #2212424
I don't understand what you mean. Can you clarify?

I'm kidding. I'm pretty much just saying that having stuff in focus is so not cool and you need to make sure your whole photo is out of focus to be cool .

Don't listen to me though, I'm nuts.

Robert, he is playing on my love for bokeh. He is also talking like a lensbaby user. LOL!

TMR Design wrote in post #2212390
Yes but what I am saying is this.

If I want to be 6 feet in front of my subject, so as not to be too close, and I am determining a DOF (and aperture value) based on that, then that istance is set. So how do I now control background blur? can't I? Increasing subject to background distance doesn't have any effect on this? I thought it did.

You're right - the further away from the subject the background is the more OOF it'll be, regardless of aperture used or camera-subject distance.

Jon wrote in post #2212733
You're right - the further away from the subject the background is the more OOF it'll be, regardless of aperture used or camera-subject distance.

Which is why sometimes people use telephotos for portraits outside (or inside for that matter), correct? You can take advantage of backgrounds this way.

A factor, but not the only reason - subject perspective enters into it also.

Jon wrote in post #2212775
A factor, but not the only reason - subject perspective enters into it also.

You mean the ability to isolate a subject from a clutter?

Telephoto will actually give the illusion that the background is closer to the subject... if that makes any sense. I need a picture to illustrate but.... take a picture of a flower with a house behind it with a wide angle lens... now pull out the telephoto, back up to get a similar FOV. The house will now appear to be closer to the flower, as if there's not as much distance between the 2.

Someone else will likely explain it in more "scientific" terms and provide helpful pics but... oh well