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22-06-2005 |
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Making Pictures
To anyone used to working with view cameras and sheet film, moving up beyond
8x10 isn’t really a new experience. It’s a bit like moving your daily workout
from five miles to eight, not like starting to run in the first place. Viewing
the brilliant oversize groundglass image is a constant reward for the extra
lifting involved in using big cameras. Once an outfit is assembled, the most
persistent problems revolve around the effects of the long lenses required by
ultra large formats. At 12x20 format, even a short lens may be an impressive
fourteen inches (360mm) and its hyperfocal distance for f/45 is 46 feet. That
is, even at f/45, depth of field will extend only from 23 feet to infinity.
Hyperfocal distance at f/90 will be 23 feet. Longer lenses give dramatically
less depth of field. Careful decisions about focus and judicious use of swings
and tilts are needed.
Bokeh, the way a lens renders out-of-focus areas, is usually
of more concern in small format work than in large format where it’s common
to arrange for everything in the frame to be in focus. That’s often just not
possible with ultra-large formats, so a lens that gives pleasing transition
from sharp to out-of-focus areas may be vital to successful mammoth camera work.
Reciprocity failure is no different for big films than for small ones, but it
has to be dealt with more frequently. With typical b&w films like Tri-X or HP5-Plus,
exposures in full sunlight at f/64 are in the 1/4 second range, and will reach
to full second or more in shade or overcast. That will require even more exposure
to compensate for reciprocity failure.
Still more exposure compensation will
often be needed for bellows extension. Ultra-large formats require this compensation
for pictures that would not normally be considered close-ups, and this can fool
even experienced photographers. Half a stop of compensation is needed when the
reproduction ratio reaches one quarter life size—that’s a subject six inches
across for 35mm—but with a film twenty inches wide, it means a half stop of
“close up” compensation for bellows extension will be needed for a flat subject,
like part of a building, that’s eighty inches across! Even more confusing, when
a short lens is used for a subject in depth, the best focusing technique may
be to combine a back tilt with significant bellows extension. This picture won’t
seem like a close-up at all, but the compensation is still needed. If exposure
is already in the range of reciprocity failure, a half stop extension error
can quickly multiply to a full stop or more: enough to ruin a negative.
Bellows
extension, reciprocity failure, and limited depth of field all combine to make
close-up studio still life work with ultra-large cameras extremely challenging.
Powerful studio electronic flash units will serve better than continuous light
sources, but will still likely require multiple “pops” of the flash to build
up enough light for exposure. It can be done, especially if the subject can
be arranged to work with a shallow plane of focus and photographed at a ratio
of 1:1 or less. However, once you begin making the image on the film larger
than the actual subject, the cost/benefit ratio of the big camera begins to
decline. Most standard lenses deliver poor performance enlarging to the negative
(though some old process lenses meant for these ratios could prove useful) and
depth of field becomes miniscule. At this point, better overall results can
generally be had by enlarging from a smaller negative.
Conclusions:
Ultra-large
format cameras aren’t for everyone, and of course they’re not the choice for
every situation. But they are nowhere near as limited in use as might be thought.
I use my oversize cameras in all sorts of weather, and even to capture “action”
in the sense that fleeting lighting effects on the landscape are a kind of action
that can be captured with a bit of luck and anticipation. 11x14 and 7x17 cameras
can be portable enough for hiking to remote locations and even a 20x24 can be
used any place you can reach by car or truck. If the special look of a contact
print is right for your work, using a really big camera can actually be the
easy way out. Once you understand and master the limitations imposed by long
lenses and large film sizes, the contact-printed big negative gives results
no amount of effort will get from an enlargement. So when asked why I go to
the trouble of working with giant cameras I sometimes answer, “because I’m lazy.”
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Dernière mise à jour : ( 23-06-2005 )
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