Portrait and focal length
tsp
away from the subject and zoom in the background will be in moer focus
than if you were to stay close and use the lowest focal length on your
camera. a website said that for portraits, you want to make the
background blurry and only the subject in focus. now most people say a
80-120mm focal length is best for portraits..wouldn't this do what your
not supposed to do? make the background sharp and in focus? or does this
rule only apply to Point and shoot cameras where you cannot control the
f/stop
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Fred Whitlock
focal length. Good shooting.
Fred
Maplewood Photography
http://www.maplewoodphoto.com
tsp wrote in message <365EE6FA...@nospam.triographx.com>...
Roger Carbol
> i've read in a photography mag a long time ago saying that if you stay
> away from the subject and zoom in the background will be in moer focus
> than if you were to stay close and use the lowest focal length on your
> camera. a website said that for portraits, you want to make the
> background blurry and only the subject in focus. now most people say a
> 80-120mm focal length is best for portraits..wouldn't this do what your
> not supposed to do? make the background sharp and in focus? or does this
> rule only apply to Point and shoot cameras where you cannot control the
> f/stop
As far as "rules" go, it's not a bad place to start. All other
things being equal, a lens with a long focal length will have a
greater Depth of Field than a lens with a short focal length (in
other words, more of the background will be more in focus.)
So, why not shoot all your portraits with a 20mm lens?
For one thing, you often want as least as much Depth of Field
as the depth of the subject. If you focus on the eyeball of
your model, and his nose is out of focus and his ears are out
of focus, then that might not be the effect you want. Or maybe
it is the effect you want.
Secondly, there are perspective issues, and they ARE independent
of f-stop. A 20mm lens held a foot away from your subject will
introduce distortions, like making his nose look huge. Sometimes
you might want that. Very often, however, people are not happy
with their portraits when taken with a wide-angle, short lens.
Like many photographic questions, the best way to answer it is
probably to take your camera and see what happens when you shoot
some portraits with a 24mm lens, a 50mm lens, a 100, a 300, etc.
Experience tends to weigh much more than advice (at least that
is my advice, based on my experience.)
.. Roger Carbol .. r...@shaw.wave.ca .. eye of newt
Steve Dunn
$i've read in a photography mag a long time ago saying that if you stay
$away from the subject and zoom in the background will be in moer focus
$than if you were to stay close and use the lowest focal length on your
$camera. a website said that for portraits, you want to make the
$background blurry and only the subject in focus. now most people say a
$80-120mm focal length is best for portraits..wouldn't this do what your
$not supposed to do? make the background sharp and in focus? or does this
$rule only apply to Point and shoot cameras where you cannot control the
$f/stop
Here are a couple of things to consider - perspective and
depth of field.
Many people like to take portraits at longer focal lengths because
it tends to minimize perspective problems. The shorter your focal
length, the closer you have to be to the subject in order to get them
to be the same size on the film. The closer you are, the more
prominent their facial features will appear. The biggest thing
that people usually mention here is the nose; get in close with a
wider-angle lens and the subject's nose appears to get bigger,
which usually doesn't result in a flattering portrait.
For more information, see http://photo.net/photo/portraits.html
As for background blur, you may be surprised. It's generally
thought that there is less depth of field available as the focal
length increases. That's true - but only if you hold the distance
from the lens to the subject constant. If you do that, then you're
also changing the size of the subject's image. If you compose
the picture so that the subject's head mostly fills the frame with
your 50mm lens and then switch to a 100mm lens, you'll find that
a significant portion of the subject's head has vanished.
If, on the other hand, you change the distance from the camera
to the subject in proportion to the change in focal length, you'll
discover that you have essentially the same depth of field
(assuming the same aperture) - but now you're getting a more pleasing
perspective. See question 15 in http://photo.net/photo/optics/lensFAQ.html
for more details, including when this approximation doesn't work.
For example, using the depth-of-field calculator at
http://www.worldphoto.com/depthof.htm
if you have a 50mm lens focused at 2m and an aperture of f/2,
your depth of field is roughly 1.91m to 2.10m - so anything from
9cm in front of the focal point to 10cm behind the focal point is
in focus. Keep your background more than 10cm behind the subject's
eyes (since you normally focus on the eyes - lack of sharpness is
much more noticeable in eyes than it is on most other parts of the
face) and it won't be sharp; the farther back it is, of course,
the less sharp it will be.
Use a 100mm lens and move back to 4m (so that the subject appears
the same size) and use the same f/2 aperture, and your depth of field
is roughly 3.91m to 4.10m - so once again, anything from 9cm in front
of the focal point to 10cm behind the focal point is in focus.
It's quite possible that the magazine you read is assuming that
you can't use the same aperture at all focal lengths.
--
Stephen M. Dunn (SD313), CNE, ACE ste...@ussinc.com
----------------------------------------------------------------------------
Senior Manager United System Solutions Inc.
104 Carnforth Road, Toronto, ON, Canada M4A 2K7 (416) 750-7946 x251
Rogerio Martins de Moraes
> i've read in a photography mag a long time ago saying that if you stay
> away from the subject and zoom in the background will be in moer focus
> than if you were to stay close and use the lowest focal length on your
> camera. a website said that for portraits, you want to make the
> background blurry and only the subject in focus. now most people say a
> 80-120mm focal length is best for portraits..wouldn't this do what your
> not supposed to do? make the background sharp and in focus? or does this
> rule only apply to Point and shoot cameras where you cannot control the
> f/stop
>
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Rule of thumb: The best focal length for portrait are long ones (over 70mm).
this way you have a shalow depth of field (assuming you'll use a wide
aperture, like f4 or less). Longer lenses also distort almost nothing compared
to wide ones, let's say 38mm or less. so use a tele.