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Example of DOF in head shots

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I've been experimenting with various F-stop settings when taking head shots and thought I'd share the results here for anyone interested. I'm sure it's old news to many of you, but I hope some folks might benefit by seeing examples.

My goal was to figure out the best F/stop to use to keep the head in focus, but blur the background. In this case the background is some redwood trees about 20-30 feet behind the model.

I took the same shot at f/3.2, f/4 and f/5.6. The equipment was a Nikon D200 with a Tamron 28-75 F/2.8 lens.

For context - here's the shot without any editing:



Below I've cropped to just the eyes and nose. The focus point is always the bridge of the nose. You may have to zoom in a level to see the differences on the edges of the glasses.

F/3.2 (both sides of the glasses frame and edges of the face are out of focus)



F/4 (The glasses frame nearest the camera is now in focus, but the far side isn't yet)



F/5.6 (both sides of the glasses frame are in focus)



The experiment showed me that I should usually be using f/5.6 for the shots - or at least f/4 - to keep all of the head in focus.
 
The DOF depends also on focal length of the lens and the distance of the subject to the photographer (Camera). The closer the distance, the narrower the DOF. If you are further away, the larger the DOF. Same for focal length. The wider the angle (less focal length) the bigger the DOF and vice versa. So unless you will always be at the same distance and the same focal length, the DOF will be different.
 
The calculations I've seen for DOF certainly take focal length into account:

http://www.dofmaster.com/equations.html

j.

--------------------------------------------------------------------------------------------------------------------

'What really got me into photography and keeps me interested 30 years later is that my pictures never fully represent what I saw.

The fact that film records the world differently than I see it is always a challenge and sometimes it records it more powerfully.

And those are the images people really respond to.'
  • Galen Rowell
 
where i = 1, 2, 3,... for f/1.4, f/2, f/2.8,...

j.

--------------------------------------------------------------------------------------------------------------------

'What really got me into photography and keeps me interested 30 years later is that my pictures never fully represent what I saw.

The fact that film records the world differently than I see it is always a challenge and sometimes it records it more powerfully.

And those are the images people really respond to.'
  • Galen Rowell
 
This makes a big change. I would not deem this a standard portrait profile (subject isn't even looking that the camera). Of course straight on shots are going to be different, but this angle seems a little extreme.

But they are nice findings if you shoot the same way each time in a controlled environment.

--
If you have a moment, check out my site:
http://www.zotsandboo.com
 
The same pretty much applies to animals where you want the whole head from nose to ears in focus. f/5.6 usually does it. Went on a workshop with Andy Rouse and that is his ususal setting.

Simon
--
http://sclamb.zenfolio.com/
 
Yes and no.

DoF is actually dependent on the reproduction ratio, or the magnification of the subject.

If you fill the frame, you will get the same DoF, irrespective of the focal length. But the reproduction ration can, and usually is expressed in function of the focal length and the subject distance.

What you do get with longer focal lengths are smoother background. That's because, with a long lens, the background is more magnified.

http://www.luminous-landscape.com/tutorials/dof2.shtml
 
Here we are, some experts who seem to disagree with you.

The Photographer’s Handbook by John Hedgecoe, Page 29
http://www.flickr.com/photo_zoom.gne?id=478149671&size=o

Lenses with shorter focal lengths produce images with larger DOF. For instance, a 28mm lens at f/5.6 produces images with a greater depth of field than a 70mm lens at the same aperture. (Vincent Bockaert)
 
Three factors can affect the depth of field:
I. focal length of the lens
II. distance from the camera to the subject
III. the size of the aperture or the setting of the f-stop

http://www.azuswebworks.com/photography/dof.html

http://www.ephotozine.com/article/Depth-of-field-explained

The second control over depth-of-field is the focal length of the lens. Just considering the focal length of the lens, a smaller focal length provides greater depth-of-field; a longer focal length provides less depth-of-field.

http://www.apogeephoto.com/feb2005/jaltengarten2_2005.shtml
 
lanef said:
The second control over depth-of-field is the focal length of the
lens. Just considering the focal length of the lens, a smaller
focal length provides greater depth-of-field; a longer focal length
provides less depth-of-field.
Click to expand...
but to achieve the same reproduction ratio you should get closer to the subject. The formula you quoted simply says that both (focal length and distance from the subject) are cancelling out each other to produce the same DOF with same framing. Only perspective changes at same reproducation ratio with different focal lengths, not DOF. See page 7 here:
http://xoomer.alice.it/ripolini/Close_up.pdf

Pierre
 
I don't think the experts I have quoted are talking about reproduction ratio. This is a different matter.

I think when they are talking about focal length, it is mainly at the same distance as John Hedgecoe's example.

One more thing: Perspective has nothing to do with focal length; it is a matter of viewpoint.
Pierre Sottas said:
lanef said:
The second control over depth-of-field is the focal length of the
lens. Just considering the focal length of the lens, a smaller
focal length provides greater depth-of-field; a longer focal length
provides less depth-of-field.
Click to expand...
but to achieve the same reproduction ratio you should get closer to
the subject. The formula you quoted simply says that both (focal
length and distance from the subject) are cancelling out each other
to produce the same DOF with same framing. Only perspective changes
at same reproducation ratio with different focal lengths, not DOF.
See page 7 here:
http://xoomer.alice.it/ripolini/Close_up.pdf

Pierre
Click to expand...
 
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