DOP with portraits

Trying to figure out how most folks decide how much DOP they want for portraits..... I'm aware that for most situations unless it's a studio, one would try to use as large an aperture as possible without starting to get to many out of focus shots.

Do the folks that shoot for a living try to give themselves some wriggle room to avoid OOF...... for instance minimum 6", or 12"?

Thanks

i was trying to figure out what DOP meant but from rest of your text, i think u meant DOF ie depth of field?
and i usually pick my aperture by how much i want in focus .. some ill go for f11 if i want to show lotsa background or id go f2.8 if i just want to show the subject. i dont worry about OOF, just try to be careful with your focusing and shoot more then once.

mpstan wrote in post #11202357
Trying to figure out how most folks decide how much DOP they want for portraits..... I'm aware that for most situations unless it's a studio, one would try to use as large an aperture as possible without starting to get to many out of focus shots.

Do the folks that shoot for a living try to give themselves some wriggle room to avoid OOF...... for instance minimum 6", or 12"?

Thanks

6" or 12" is what measurement?

Not sure about "I'm aware that for most situations..., one would try to use as large an aperture as possible"

I always use the appropriate aperture for what I am trying to achieve with the photograph.

I would decide what I want to achieve with the shot and make my calculation from there.

For a portrait in front of something you don't want to emphasize or detracting from your subject (a brick wall perhaps) - you use the minimum of DOF you can achieve.

For one with a good background you might want all the background in focus (think of outdoors in a nice park).

Once I know that the aperture is easy to work out.

It was a bit late when I posted this; sorry if I was ambiguous.

I'm thinking for instance in a church, doing communion pictures..... I get one chance to photograph each child taking communion, about a 3 second time window. I'm 10ft away with my 7D and I have either my 70-200 f4 or 17-50 Tamron; usually flash is permitted; I have one time to get it right...... about 3 seconds; if I'm out of focus I can't retake. I need sufficient depth of field so that all of my images are well focused. I can't use a tripod; gotta keep moving with people walking around, communion not happening at exactly the same point on the floor etc. I want as much background blurred as possible, hence lowest f stop number, as possible..... but I want a safe cushion in terms of depth of focus so that they are all keepers with all body parts in focus.

Should I be able to get all keepers with a 9" depth of field on a side shot of a child and their body?? 6"? 12"? What's the lowest realistic number an experienced person could use and still have good results? I could dial up f/5.6 and be done with it but then my background won't be quite as blurry..... so I'm trying to get a sense of experienced folks' thought process would be in this scenario. If I had my 50mm 1.8 on and tried shooting closer at f/1.8, I'm looking at 6" DOF at 8ft distance. I don't know if I should be thinking 1. I'm dreaming, too sharp, will have some out of focus pics, or 2. Hmm, 6 inches, I should be just fine, if my spot focus hits his neck or his ear, I've got a good enough margin, I should be ok.....

Does that paint a better picture of what I'm looking for?

Thanks

DOF is a factor of aperture and focal length. The shorter focal length lenses will get you more DOF. But another key factor here is that you need to watch your shutter speed. Too slow and you will get motion blur, subject AND camera. 10 feet away I would probably use the 17-50. The aperture I would use would depend on if I wanted a tight crop, or wider view and how much I wanted the background to be visible depending on how distracting or not it is.

Each environment and scenario is different ... which is why you will not get an absolute answer here.

As you are allowed to use flash, read THIS thread from the Strobist site.

If you have sufficient separation, rather than worrying about DOF, you can underexpose the ambient such that the background tends towards black and use the flash to provide the light for the subject and any 'freezing' of any movement as may be necessary by dent of using a slower shutter speed.

I understand DOF. I know how to use tables or my iphone to determine it for a given lens, aperture and subject distance.

In my example I stated I wanted maximum background blur, and I know I need to keep my shutter speed fast enough to avoid image blur. I think I have enough light in my example to accomplish a fast shutter especially if I adjust ISO.

Would you go ahead and shoot away in my example if the calculations said you would have a 6" depth of focus? I have, and I've been burned because some (not many) of the images were out of focus. So I wish I would have stopped down. That's why I am asking how you would go about determining your f stop in my above described scenario, assuming your shutterspeed wasn't a problem.......

DunnoWhen wrote in post #11205957
As you are allowed to use flash, read THIS thread from the Strobist site.

If you have sufficient separation, rather than worrying about DOF, you can underexpose the ambient such that the background tends towards black and use the flash to provide the light for the subject and any 'freezing' of any movement as may be necessary by dent of using a slower shutter speed.

Thank you DunnoWhen, didn't see your post when I was posting. I'll read your link.

mpstan wrote in post #11205994
I understand DOF. I know how to use tables or my iphone to determine it for a given lens, aperture and subject distance.

In my example I stated I wanted maximum background blur, and I know I need to keep my shutter speed fast enough to avoid image blur. I think I have enough light in my example to accomplish a fast shutter especially if I adjust ISO.

Would you go ahead and shoot away in my example if the calculations said you would have a 6" depth of focus? I have, and I've been burned because some (not many) of the images were out of focus. So I wish I would have stopped down. That's why I am asking how you would go about determining your f stop in my above described scenario, assuming your shutterspeed wasn't a problem.......

Again... it depends. How much do you want in focus... just 6". Is the subject moving perpendicular to the plane of focus? How much? How fast? Are you moving perpendicular to the subject? How fast are you triggering the shutter after an AF lock?

The more variable these answers are mean that yes, you should build in a little padding to account for shifting focal plane. How much depends on how much and how fast the shift may be. You could also shoot in AI Servo, or some AF tracking mode if the movement is constant and/or predictable.

DunnoWhen wrote in post #11205957
If you have sufficient separation, rather than worrying about DOF, you can underexpose the ambient such that the background tends towards black and use the flash to provide the light for the subject and any 'freezing' of any movement as may be necessary by dent of using a slower shutter speed.

Yes, if you are using a stopped down aperture to inflict the underexposed ambient to also gain DOF.

Careful with doing this as it can cause a very 'snap shot' looking image. If you use on-axis/on camera direct flash as the main light source it will be very harsh and cast nasty shadows in an underexposed background ambient situation.

mpstan wrote in post #11205994
I understand DOF. I know how to use tables or my iphone to determine it for a given lens, aperture and subject distance.

In my example I stated I wanted maximum background blur, and I know I need to keep my shutter speed fast enough to avoid image blur. I think I have enough light in my example to accomplish a fast shutter especially if I adjust ISO.

Would you go ahead and shoot away in my example if the calculations said you would have a 6" depth of focus? I have, and I've been burned because some (not many) of the images were out of focus. So I wish I would have stopped down. That's why I am asking how you would go about determining your f stop in my above described scenario, assuming your shutterspeed wasn't a problem.......

Something I'm not clear on -- you say you have gotten out of focus images -- in what way were they out of focus? If you mean that you had a little bit in focus but other parts of the image were out of focus, then of course you need to narrow your aperture and concentrate also on getting the important parts of the image in the right plane of focus. But if you mean that the whole image was blurred, that would mean that you probably had a slow shutter speed and the flash, if you used it, could not compensate for your movement or the movement of the subject.

So, how to solve this depends on what caused it. I'd be a bit less picky about the exact aperture, although I'd say shooting at f/2.8 would be pushing things a but unless you had to to get a fast enough shutter speed. But if you are using flash at 10 feet away I'd think more of the f/4-f/5.6 range, and keep your shutter speed fast enough to work with the flash to effectively "freeze" camera or subject motion. But all this will depend on different things and you will with experience need to get a feel of the conditions and environment.

Is there any reason that you cannot "practice" at the site beforehand...maybe even using a doll or something?
Would give you an idea of the lighting and other things necessary for making the decisions that you're asking about.

Sorry everyone, of course I meant DOF, not DOP.... I appreciate all of the input.

I'm usually trying hard to keep my shutter up at safe speeds and now that I've upgraded from my 10D to a 7D I think I can do so more effectively with higher ISO's. Most of my blurring I think is coming from OOF and I think it has been due to shooting wide open. I guess part of me is curious to know if more gifted photographers have the same issue or if I just need to get better at focusing.

I hope to do more photography in our parish. Sometimes I can use flash, sometimes not depending on the priest. I try to meter for ambient if I can, then fill flash if I'm permitted.

Good idea practicing beforehand. This would definitely help me gain comfort in how wide open I can shoot. Using flash of course I have much more latitude to stop down. Without flash, in this church, it is always a challenge balancing sufficient exposure with properly focused images. I've not taken my 7D to this church, but will soon. Looking forward to seeing what it'll do.

Thanks everyone

You're selecting one focus point and not recomposing after, right?