Hi,
The focal length appears to be somewhere in the 75-135mm range
(assuming it's shot on 35mm). It is not a very wide aperture because
the depth of field keeps quite a lot of the head in reasonably sharp
focus. For a 35mm camera using a 100mm lens I'd guess it was about f/5.6.
The background is dark because it's night time - it's a flash shot.
And there is nothing very close behind the soldier's head, so the
background blur is quite smooth. The number of sides on the highlights
is the same as the number of diaphragm blades in the lens. This is also
a bit of a clue about the size of the aperture because a wide-open
lens produces a circular highlight, whereas the more stopped down it
is the more obvious is the polygonal shape of the aperture.
I would recommend you use a lens in the range 85-135mm if you want to
try this kind of shot. 85mm lens are generally available with
apertures as wide as f/1.4, but they tend to be very high quality and
correspondingly expensive. You could get a good 85/2 lens for a much
better price and this would also allow you to experiment with background
blur. To get a really nice effect you could do a head shot against
back light through the leaves of a tree, exposing for the subject's face.
Make sure the background is way, way back from the subject - ie he's not
standing against a wall or something. Make the shot at several different
aperture/shutter speed combinations to judge the effect of the varying size
of the aperture on the degree of blur.
This photo (http://www.web-options.com/ethiopia/index.htm) shows something
of the effect, and it was taken with a cheap zoom with a maximum aperture
of f/4. Although it's not backlit it shows a nicely blurred background
which helps to abstract away that person in blue behind the subject,
and it demonstrates that the effect is easy to get without special equipment.
Hope that helps.
---
Bob
mailto:[EMAIL PROTECTED]
Sunday, March 04, 2001, 8:58:01 AM, you wrote:
> Can I refer you to the following image I came across:
> http://www.defenselink.mil/photos/Feb1998/980119-A-6522J-503.jpg
> The dark, blur background and the 9-sided image of a
> light source far into the background suggest that this
> photo is taken with a very big aperture. (Please
> correct me if I'm wrong)
> Can you suggest at what aperture and focal length that
> photographer took the photo at? I would like to buy a
> lens that allows me to shoot this kind of photographs.
> Thanks,
> Kelvin
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