At 01:31 PM 10/10/2001 -0400, Tina Turgeon wrote:
[snip]
>When I took the portraits of my dad, I used the split part to
>focus, but it's not focused correctly so I'm wondering where I
>went wrong. I'm also wondering if I should not only depend on
>the split, but also look at the matte area. That's why I'm
>curious to find out if others really need/use that aid.
Tina:
I'm assuming that your portraits were primarily of your dad's
face-and-shoulders (i.e., the classic "bust" portrait), so take my comments
accordingly. I'm also assuming that you were using a normal lens.
Most people instinctively use the split-prism part of the focusing screen on
sharp edges, because they give the best indication of focus. When the edge has
no discernible "break" or "jog" in it, you assume the image is focused.
Unfortunately, I've noticed that a lot of people also do this with facial
portraits. Now, typically, the best edge that a facial portrait usually
provides or offers is the profile or outline of the head, which, when the face
is viewed straight on, means the side of the head around or above the ears.
So, I've noticed that people (and I used to do this a *lot* myself) will focus
on that area, and then assume that the focus is good for the portrait.
Unfortunately, if you're close to the subject or have a shallow depth of field,
this has probably led to a mis-focus. The parts of the human face that people
typically pay the most attention to (and are therefore usually most critical to
get in to correct focus) are the eyes, mouth and nose. However, these elements
of the facial expression are a good four to six inches (10 to 15 centimetres)
*in front* of the edge or profile of the typical human head when viewed
straight on. At shallow depths of field, focusing on the head profile as
defined above will cause the centre of attention to be slightly (or perhaps
even significantly) out of focus.
This problem can be exacerbated by slight back-and-forth motion by either the
photographer or the subject (or both!) after focusing. Many professional
portrait photographers try to minimize this source of error in one of several
ways: greater depth-of-field (smaller aperture), fixing the camera's position
(tripod or some other support), or fixing the subject's position (comfortable
seating on a chair or stool, prone or supine positions, etc.). All of these
can be combined in various ways, of course.
One solution (assuming you've got sufficient light for contrast and you're
close enough to see the details) is to use the split-prism aid on one of the
"centre of attention" features: the lines or edges of the eyes, mouth or nose.
Another is to use the matte portion of the screen (assuming you have such a
screen) to try and see at what point your focus appears to bring out the most
detail in the "centre of attention."
And of course, practice, practice, practice... I'm still working on that part.
8^>
Garth
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