focus point question

CC92713

CC92713

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Christian Elizabeth
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I am switching to manual mode and my question is this.... When taking a portriat with more than one person can you have two or more focus points? if not where is the best place to focus? so far I have only really been shooting people alone but wondered what you do in these cases
 
theres only one focus point ,,,( although different things in the frame may be in or out of focus ) for portraits the focus is on the eyes ,unless you dont want it there of course . for more than one person ,you could try to get them both about the same distance away from the lens ,of use an aperture that gives you a greater depth of field
 
If they are standing next to each other, then as mentioned try and get both pairs of eyes the same distance from the camera. It is more difficult if you are filling the frame , and you are wide open, and fairly close.
It is a little more difficult if they are standing one in front of the other, because the depth of field needs to be much greater to get the zone from the rear person's eyes through to the front eyes in focus. A much smaller aperture will need to be used in that case.
 
Either get the subjects on (or as close as possible) the same plane of focus or stop down enough to get the required DoF.
 
The general rule for a couple would be the closest eyes, then drop your aperture to ensure sufficient depth of field.
 
CC92713 said:
I am switching to manual mode and my question is this.... When taking a portriat with more than one person can you have two or more focus points? if not where is the best place to focus? so far I have only really been shooting people alone but wondered what you do in these cases
Click to expand...

The most popular method is focus-recompose technqiue. Set the camera to centre AF point only, focus on the area you want sharp and lock that by holding half-pressure on the shutter release. Then recompose the picture as you want and shoot. Many folks find it easier to switch AF activation to a button on the back, and deactivate it from the shutter release - so-called back-button AF, see handbook.

But this sounds like a depth of field question. There is only ever one plane of sharpest focus, with a zone of acceptable sharpness both in front and behind the point focused on. This zone is called the depth of field.

DoF varies according to focal length, distance and f/number. Check what you're getting with this on-line DoF calculator http://www.dofmaster.com/dofjs.html It's not as complicated as it looks - just select your camera from the pull-down menu at the top left, and this selects the parameters appropriate to the size of the sensor. Then input focal length, lens aperture f/number, and the shooting distance, and all the answers appear on the right.

To your specific question, a handy rule of thumb with groups of people is to focus one third in, from front to back - ie a bit in front of the middle person, as there is always a bit less DoF in front of the focused point than there is behind it. However, this varies and the 'one third in' rule doesn't work for everything, most notably distant landscapes.

In practise, lens aperture is the easiest way to control DoF - higher f/numbers give you more of it, eg f/8 or f/11.
 
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On that DOF calculator, what value to input for focal length? ie on D7000 do I need to take into account of crop factor? If yes, then with 35mm lens, the value is 50???

Was pondering about this and hyperfocal. Weather's not that kind these days to go out for field test but was giving a quick read on hyperfocal. As an example with D7000, 35mm, f5/6 and subject at 25ft the result for hyperfocal is 35.6ft. So is this a correct statement:

  • Instead of focussing on subject@25ft, focus on something which is approx 35-36ft?
    OR
  • Move subject near to 35-36ft?

Normally subjects are peoples. Until now, as long subjects are sharp and correctly exposed, I was prepared to sacrifice on backgrounds/surroundings. But if improves overall quality, then why not.

Thanks.
 
bbk said:
On that DOF calculator, what value to input for focal length? ie on D7000 do I need to take into account of crop factor? If yes, then with 35mm lens, the value is 50???
Click to expand...

No you don't have to take the crop factor into account. When you tell the DOF calculator which camera you're using it knows if it's FF or DX.

Was pondering about this and hyperfocal. Weather's not that kind these days to go out for field test but was giving a quick read on hyperfocal. As an example with D7000, 35mm, f5/6 and subject at 25ft the result for hyperfocal is 35.6ft. So is this a correct statement:

  • Instead of focussing on subject@25ft, focus on something which is approx 35-36ft?
    OR
  • Move subject near to 35-36ft?
Click to expand...

Hyperfocal distance is a matter of the physics of the focal length of the lens and aperture - distance to subject doesn't enter into it. Change the subject distance to 100ft and DOF calculator will give you the same answer for HD as 25ft. In your example your subject would be out of focus because it is closer than the near focus limit (26.3ft).

Normally subjects are peoples. Until now, as long subjects are sharp and correctly exposed, I was prepared to sacrifice on backgrounds/surroundings. But if improves overall quality, then why not.

Thanks.
Click to expand...

HD focussing is generally used in landscape photography where you would focus the lens at the HD to get as much of the scene as possible acceptably sharp. If you're shooting people then just focus on them. If you want the background in focus set a small aperture (or a large aperture for out of focus backgrounds).

Hope that helps :D
 
Thanks for all the help:)
 
thanks steve...that's cleared 2 questions. About the 3rd one, the kind of pics is "contextual" though not sure of the term. It's not about persons but placing subjects in context to whole background. storytelling???

And yes that's what I've been doing setting small aperture but was wondering whether HFD will improve a bit??? Forgot to add: subjects little softer and noisy than the background.
 
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bbk,

Not entirely sure I get your meaning but if you are talking about having people in a landscape shot but not the subject of the shot then yes, HFD works well. The only problem with doing that is people tend to expect humans in a picture to be in focus and if they're not then the whole image "appears" out of focus.

Does that help?
 
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