| You’re asking the right questions.
I’d hang onto your Nikonos for use as a backup in case
of trouble with your housed system or as a special purpose
camera—with close-up kit or extension tube, for example.
You may even want to carry your Nikonos as a second camera
on a dive. There are some advantages to a Nikonos over a housed
camera—even as a macro system. Make no mistake, there
are many more advantages to using an SLR camera system for
macro photography, but you’ll probably have an edge
with both systems at hand. It’s easier to quickly visualize
and vary your lighting when you don’t have your eye
stuck in the finder of a housed camera. This advantage can
be exploited when taking certain types of photographs of both
hard and soft coral, fans, and such. Sometimes you need to
see the exact image as it will appear in the frame, and SLR
is a must. At other times, you may have a general idea of
a range of acceptable renditions of subject detail, and nuances
in lighting are the objective.
There is simply no substitute for water contact optics when
it comes to sharpness, contrast, and color saturation in an
image on film. Nikonos lenses are designed from the ground
up to be used underwater. Without getting into a bunch of
optical physics, let’s just say that whenever light
passes between two mediums with different refractive indexes,
light rays are bent. Nikonos lenses are optimized to perform
best when the front element is in contact with water. When
you places a lens in a housing, the port becomes part of the
optical system. A flat port will magnify the image. A dome,
in its self-appointed function as a lens element, will form
a "virtual" image in front of itself, and the camera
must now focus on this virtual image. Loss in image quality
when shooting normal to longer lenses behind a flat port is
real hard to demonstrate. Loss in image quality when shooting
wide-angle behind a dome is substantial. This is especially
noticeable when examining sharpness at the edges of the photograph.
Had somebody told the lens designers that the optic would
be used underwater in a housing, and that performance in air
was of secondary performance (as it is to most underwater
photographers, even though we tell our significant others
that the lens is really for photographing the kids since we
didn’t buy it for an underwater camera), it could have
been designed to yield much better edge-to-edge sharpness
in a housing. All that needed to be done was to tweak the
shapes of all or some of the five to twelve or more elements
in the lens to account for the bending of light caused by
the water-to-plastic and plastic-to-air interfaces produced
by the dome port. When you add this to the fact that you are
virtually always placing your superbly designed and crafted
(as well as exquisitely expensive) lens behind a forty-dollar
compass dome (cheaper in quantity), it becomes predictable
that the Nikonos is capable of delivering superior image quality
when used in water. If you want to have a greater appreciation
for the difference in optical designs for use in water and
for use in air, just look through your Nikonos fifteen or
twenty viewfinder out of the water sometime!
Will the Nikonos lens actually produce a better image on
film? Yes! If the focus is good, and, of course, if everything
you saw in the viewfinder and wanted in the frame made the
cut. Since you have to estimate focus distance with the Nikonos,
and since you’re looking through an accessory viewfinder
and not through the taking lens when composing, composition
and focus are up for grabs. This now becomes a matter of skill
and luck.
So much for theory—let’s look at what’s
happening out there. M Some of the very best professional
photographers use only housed cameras—for everything!
You’ve seen numerous wide-angled photographs taken with
housed cameras, published on covers of this and other fine
magazines, including National Geographic. They look real good,
don’t they? So, apparently, we got incredibly lucky
with the afterthought of an add-on dome port for shooting
underwater with lenses wider than about 28mm. Yes, on critical
analysis, sharpness does fall off toward the edges of the
image. If you viewed the same image photographed with a Nikonos
lens and with a housed lens of similar angular coverage side
by side, the Nikonos shot would certainly have brighter, more
vibrant colors to it, as well as that certain pop that outstanding
contrast provides. But then, you never view two such images
side by side! The fact is that even gallery prints of images
produced with housed cameras blown up to forty by sixty inches
huge can look great when viewed from a distance. It seems
that a certain amount of unsharpness is kind of expected or
at least accepted in an underwater wide-angle shot, as long
as those parts of the photograph that strongly draw the eye
are reasonably close to customary sharpness—whatever
that is.
|
