Hi Jan,
Very interesting post. My interest is photographing the thinks I 'cannot' see
well. Close-ups / Macro (Love to photograph the small details of small living
things) and wildlife (Blood vessels on a deer's antlers in velvet or water
dripping from a ducks bill) with Tele's.
Any thoughts?
BW
jans@xxxxxxxxxxx writes:
<<
The 50mm lens corresponds to roughly a 45 degree angle of view, which is
what perceptual psychologists call "the circle of attention." You are
fairly aware of happenings within this angle, although you cannot give the
entire circle your complete attention, so your eyes constantly sweep around
within this angle. This is similar to how most 50mm prints are composed.
When one views a 50mm print, one's eyes rove over the surface, picking up
details here and there. It also tends to be the angle of view most
drawn/painted by artists.
At less than half that angle -- about 10 to 20 degrees, you have the
"circle of focus." This corresponds roughly to the short telephoto range of
100mm to 150mm. This is where a viewer's eye is resting while doing all
that scanning within the circle of attention, and typically corresponds to
the diameter of nearby objects, such as faces, plants, desktop items, etc.
This is why such lenses are used for portraits, because the eye/brain says
"I recognize this, it's something I'm used to focusing on." The eye tends
to travel less when presented with such a print, instead dwelling on
textures and nuances of lighting. Such short telephoto lenses compress
distance and produce a flat-field effect -- it's interesting to note that
portrait artists also tend to draw or paint with flattened perspective.
At about double the circle of attention is the "circle of perception." 110
degrees (about a 17mm lens) is the angle within which one can perceive
objects (especially in motion), but must then move the head to bring these
objects within the circle of attention to fully image them on the densest
part of the retina. At angles of from about 70 degrees up to about 110
degrees, viewers will spontaneously move their entire heads, rather than
cruise with their eyes, as they would normally do within the circle of
attention. These angles correspond to lenses of roughly 35mm to about 17mm.
When viewing such prints, people tend to move up closer, to the point where
their heads actually have to move to take it all in.
Of course, it's the angle of view, not the millimeters, that is important.
I believe the focal length of the human eye is actually 6mm to 8mm, with a
dark f ratio of about 1.4. Perhaps this is why many 50mm lenses are made
with an f ratio of 1.4 -- the depth of field should then match that of the
dark-adapted eye. (Don't hold me to these numbers -- it's been years since
school, and my perceptual psychology textbooks are all buried in boxes
somewhere...)
(Whew... don't give me caffiene and put me in front of a keyboard!) Getting
back to Richard's point, I don't think your vision is significantly
different than anyone else's -- it's the biological neural network computer
behind the optics that makes the difference! :-) Although there are minor
variations, these three circles are fairly constant for normal humans. What
a photographer or artists "sees" has much more to do with what they are
trying to express, than with any physiological effect.
>...I'm not
>a great fan of wide angles.
Let me go way out on a limb here -- I'll bet you, Richard, that you tend to
be introverted (rather than extroverted), and judgemental (rather than
perceptual). These are personality traits that have been correlated with a
high degree of interest in the circle of focus -- life is in the details.
Extroverted, perceptual people tend to have high interest in the circle of
perception ("Just give me the big picture!"), with most of us "normal"
people falling somewhere in between.
: Jan Steinman <mailto:jans@xxxxxxxxxxx> >>
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