Depth of field -- Christmas Portraits

If you own a "fancy camera" your friends and family want portraits.

I am still working on learning to shoot landscapes (things that do

not move) and wildlife (things that move, but do not complain if the

pictures are poor).

 

I understand that when taking a portrait of one person, I can shoot

at 2.8 (I'm using a Canon 70-200 on a Elan 7) and the shallow depth

of field will blur the background. What happens if this shallow

depth of field is used with a family shot? If I place the subjects

in the same plain -- approximately the same distance from the camera,

will all be in focus?

 

When photographing more than one person where should I focus? How

about if the people are more than one row (different distances from

the camera)?

 

Is there a rule of thumb f-stop for group portraits?

 

Monte

if every one is in the same plane, the depth of field will be the same all the way across. if you photograph one or any number of people in the same plane, they should all be in focus regardless on whom you focus. as far as different planes of focus, that is more than one row, you should use an f stop that will accomodate the depth of the rows. to do this, some lens have feet/meter readings that will show the depth of field, or there are tables to use. the depth of field and sharpness depend on how close the subjects are to the camera. i recommend a very simple camera book to explain this to you. it is not very complicated. if you use a tripod and cable release, stopping down the lens (using higher f stop numbers) will probably be okay for you. generally, i focus half way between the near and far points of interest.

Your camera has a depth of field preview. Press it and check it to see

what's sharp and what's not. Play with the f-numbers to get the desired

area in sharp focus. Reading of a good book is the best approach to learn the basics.

I use to have a couple of older EOS cameras (620 and 630), and they had a "depth" mode, which made these types of shot easy. You auto-focus on the part of the scene that needs to be in focus that is closest to the camera, then auto-focus on the part of the scene that needs to be in focus that is farthest from the camera. Now the camera would set the lens to the correct distance and select the aperture that would give that desired zone of focus. Does the ELAN 7 have this mode? If it does, you might get better results with a slightly shorter lens like a 50mm, which would allow better DOF for a given aperture.<P>

 

Essentially, this mode is just doing what manual photographers have done for years using the DOF marks on the lenses.. which are now mostly missing from zooms.<P>

 

<I>Is there a rule of thumb f-stop for group portraits?</I><P>

 

For me yes... Use prime lenses with good depth of field marks. Set the zone of needed focus via the marks, and then for even better results, use one more aperture. For example, if I use f/8 to give me the needed 5-9 feet (or what ever you need), then I set the aperture to f/11. Of course, you will probably be in the shutterspeed range that needs better than hand-held stability, so use a tripod.

Depth-of-field is a function of image magnification, regardless of lens focal length. (And a telephoto lenses is definitely preferred for portraits (at least twice the focal length of a "normal" lens - any format camera).

 

 

For example: if you shoot a group of people, full length, and for the sake of discussion, the individual head size is about 1/4" on the (35mm) film plane, You could set your lens at F:1.4 and still get a reasonably sharp background (even a 1/2 mile away). On the other hand, on a head shot, if the head alone fills the entire film frame, even F:16 may not be enough keep everything from the nose to the back of the head acceptably sharp.

 

For reference, "acceptably sharp" is somewhat subjective. Although it is based on the maximum allowable size of the circles-of-confusion, and there are published guidelines, there are no hard and fast dictates as to a specific maximum. In fact, not only can it vary from interpretation to interpretation, it also varies (rather consistently) from one format to another. And with respect to circles-of-confusion (all other things being equal), a 35mm lens can cut twice as sharp an image as a 4x5 lens!

 

 

There a general rule about the RATIO of acceptable sharpness, which is: Depth-of-Field provides for one unit of distance in front and two units of distance behind the point of focus to be acceptably sharp. The actual physical distance is dependant on both the image magnification and the F:stop used.

 

 

By the way (this one drives me nuts!), You may hear the term "Depth-of-Focus" tossed about. There is NO such thing as "Depth-of-Focus"! It DOESN'T EXIST! There is only ONE POINT of FOCUS (no lens can focus on two different distances at the same time!) Everything else is "Depth-of-FIELD"! And any yahoo who uses the term "Depth-of-Focus" is blowin' it out their ear and I'd take anything they say as a grain of salt (a very small grain)! - End of rant.

 

 

You might also want to pick up Kodak's "Professional Photoguide" book (R-28, cat 104 2282) which offers a tremendous amount of information, including some depth-of-field scales. (It may not have your lens/format combination in their circular rule, but if you play with the dial a bit, you should get a much better grasp on the principles.)

Gary said:

 

<i>By the way (this one drives me nuts!), You may hear the term "Depth-of-Focus" tossed about. There is NO such thing as "Depth-of-Focus"!

It DOESN'T EXIST! There is only ONE POINT of FOCUS (no lens can focus on two different distances at the same time!) Everything else

is "Depth-of-FIELD"! And any yahoo who uses the term "Depth-of-Focus" is blowin' it out their ear and I'd take anything they say as a grain

of salt (a very small grain)! - End of rant.</i>

 

<p>When I've seen Depth-of-FOCUS used, it is usually refers to the depth of field at the film plane. That is to say, Depth of Focus refers to how much your film can be out of registration and still produce a sharp image. With LF this can be a concern when trying to achieve maximum sharpness.

f/2.8 will be too shallow. I would start with f/5.6 and work

between there and f/8 (really). Control the blurring of the background by keep the distance between the subjects and the background a large multiple of the distance between the subjects and the camera. In other words, try to keep the background far away. Ideally, the lighting will help separate the subjects from the background (via backlighting, for example), and good posing will direct the viewer's attention to the subjects.

I agree with Andy...

 

I never shoot a group portrait at less than f/5.6. And, more often than not, I am at f/8.

 

The reason for this is really simple. It is often difficult for me to pose a family in a way that would allow me to have a really shallow DOF, and, at the same time, get a natural, even pose.

 

Thanks,

Hello Monte,

 

I would use f8 at the widest for group photography. f 11 or f 16 would be preferred. Focus 1/3 the distance into the shot.

 

Gary said.."no lens can focus on two different distances at the same time "

 

Any lens can focus on two different distances at the same time if it's mounted on a view camera and a tilt or swing is applied to the front standard or rear standard. This principle of optics is perhaps the most important of the view camera's unique capabilities.

Brooks Short said:

Any lens can focus on two different distances at the same time if it's mounted on a view camera and a tilt or swing is applied to the front standard or rear standard. This principle of optics is perhaps the most important of the view camera's unique capabilities.

 

 

Yes, you have a point. However the original poster was speaking in the context of a simple 35mm camera (Canon Elan) regarding acceptable sharpness around the subject. Referring to large format adjustable cameras (i.e. swing, tilt, shift), is to a great extent, a whole different animal and I would have rephrased to say "plane of focus" (of which, there is still only one).

 

 

With all due respect to all, I can never quite understand that when a neophyte asks a basic question, instead (or in addition to) providing a simple, direct, comprehendible answer,- people feel compelled to impose marginally related, sometime esoteric and finite exceptions or topically unrelated dissertations which most invariably will confound, more than clear up the original poster's question.

 

 

At any rate, ya'll have a safe and joyous holiday season.

GARY,

 

I did give the poster a succinct answer to his question. I recommended f 8, preferrably f 11 or f 16 for adequate depth of field in a group portrait.

 

I didn't mean any offense to you with my later post regarding tilts and swings on a view camera allowing a focus on 2 seperate distances.

 

When you make an absolute statement, in capital letters, that is not accurate, you can expect someone might take objection to it.

 

And you never know, maybe my comment will spark an interest in view cameras and how they work.

What makes Photo.net so useful is that the answers don't just stop with the basics.