I'm sitting here looking at my old engineering texts on Maxwell. Initial
portions refer to point sources. Later portions refer to line sources (if
you're a comm guy, think wire antennas) others refer to area sources (if
you're a comm guy, think aperture antennas). The differences between the
three is only a wee bit o' calculus. If the phase of the energy from any
point on the line or in the area is mathematically related to the phase at
another point on the line or in the area, it's coherent energy. Laser light
is coherent and falls off as one over distance squared once outside the near
field of the emitter. (related to emitter length squared / wavelength). We
are dealing with non coherent light. Modify the same formulae for random
phase and polarization. Noncoherent light falls off as the distance squared
without a near field effect. Since we are imaging, we are dealing with point
sources, but of non coherent light.
That is all neither here nor there.
Play with it all you like, if you enlarge a photo such that any dimension of
the photograph is double the dimension it had on a previous enlargement, you
will have spread the same amount of light over four times the area or 1
forth the illumination per unit area of the print. Now, we are using lenses,
not pinholes, so another question must be answered. Wher is the reference
from which we double? Is it from the film to the print or from the lens to
the print?
Regards,
Bob...
-----------------------------------------------------------------
"The art of taxation consists in so plucking the goose
as to obtain the largest possible amount of feathers
with the smallest possible amount of hissing."
- Jean-Baptiste Colbert,
minister of finance to French King Louis XIV
From: Herschel Mair
James Clarke Maxwell is referring to a point source of light.
Light which is optically modified does not fall off at this universal rate.
At least not in the human scale
Professional LASER, for instance hardly falls off al all within a few
kilometers
Herschel
Bob Blakely <Bob@xxxxxxxxxxx> wrote:
From: 2005-06-24 kl. 10.00 skrev kpp@xxxxxxxxxx:
just a-wondering...
does the law of light intensity dropping i proportion to the square of
the distance apply to B&W enlargers?
On the macro scale (above the scale of particle physics), intensity drops
off as the square of the distance for all electromagnetic energy, including
light, all the time, everywhere in the universe. It's the law. No
exceptions.
Consult James Clerk Maxwell for more details regarding this amazing
phenomenon.
Regards,
Bob...
-----------------------------------------------------------------
"The art of taxation consists in so plucking the goose
as to obtain the largest possible amount of feathers
with the smallest possible amount of hissing."
- Jean-Baptiste Colbert,
minister of financ e to French King Louis XIV
Herschel Mair
Head of the Department of Photography,
Higher College of Technology
Muscat
Sultanate of Oman
Adobe Certified instructor
+ (986) 99899 673
www.herschelmair.com
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