Moose wrote:
> How quickly you shift*:
>
Hey, I can be as fickle as the next person. :) Some would call it being
"open minded". I hate being a stick-n-o-mud. (manditory logging
reference). My OM'ness is already as recalcitrant as a person should be.
> Interesting idea. I wonder how the lens issue would work out. Hmmm ...
Assuming FF is adequate for the vertical dimension, you'd need 24x68 mm
> coverage to match 6x17 cm film. Three 36 mm wide frames should provide
> the overlap for the 68 mm panorama, especially as the captures are just
> parts of the same images.
>
Probably what I should do is illustrate this through application. There is
more to this than "specifications". There is a real-world usage here.
The widest commonly available lens for 4x5 cameras covers approximately a 90
degree FoV. Obviously, there are smaller-format lenses which will cover
wider, but for a 4x5 film format, with a large enough image-circle to allow
or shifting and tilting, this is substantial. So, what this means is for
building a pano using a smaller capture format you are still restricted to a
maximum FoV of 90 degrees. If 90 degrees is not enough then you must seek
out other options, such as a rotating base.
For many panos, it isn't about getting the widest FoV possible during
capture, but to provide the widest FoV for viewing. Panos are not
necessarily about capture width, they are about display width. It's
specifically about presenting an image with a wider than normal format which
can actually be a telephoto shot.
A 6x17 has a physically wider physical capture surface than 4x5, but the 4x5
cameras have distinct advantages over the typical 617. 4x5 cameras allow
the lens board to be shifted and tilted. Why is this important? Shifting
is extremely important for keeping buildings from leaning over or worse-yet
in panos, leaning into the picture. One photo in my life of keeling over
buildings is enough of a special effect. But you can't do commercial work
surviving solely on keeling over buildings. The clients may want their
buildings to look a bit more, uh, proper?
So, with the 4x5, you can use swings and tilts for perspective control as
well as focus manipulation. Standard fair stuff for large-format
cameras--really the only good reason to even shoot large-format anymore.
Image-Quality is generally not that big of an advantage unless you are
talking about B&W.
So why is this digital-camera adaptor for 4x5 so important? How can it be
used effectively?
One must recognize that first of all, the absolute limit, in practical terms
for most of us, is 90 degrees FoV. If this restriction is acceptable,
continue reading. If not, then resort to pano-stitches using a rotating
base.
I envision this as being used in conjunction with the ground-glass focusing
screen. You would compose the image on a modified ground glass with
markings showing the capture area of the digital adaptor. Once the image is
composed, you replace the ground glass back with the digital adaptor and
camera. The ground-glass focusing screen would have to be different than
the standard one because the focus screen would have to be extended backward
far enough to match the same plane as the sensor.
At this point, with the camera in place, you slide the camera to the far
left and take a picture. Then you slide the camera to the right x-amount of
mm to provide a usable stitch-zone, take a picture. Repeat till you reach
the right-hand side.
The resulting merge will work extremely well because you are using only one
lens in only one position. Any fall-off occurs naturally across the image
circle and you will not need to fight any lens distortion between frames.
Each image fits perfectly with the ones next to it.
Granted, the physical capture area isn't nearly as wide as the 6x17, but
with the reduced capture height (assuming 36mm with a 5Dmk2) the
height-width ratio will be similar.
I've been doing exactly this with the 35/shift lens. With the E-1 I can take
five images (horizontal to provide a wider than normal display print),
combine them in seconds with minimal fuss. If I capture with film instead of
digital, I take only three pictures, scan and combine the results.
The reality is, one can capture a wider-than-90 FoV with the hybrid
digital-4x5 system. Not only can you shift the camera across the "film
plane", but you can shift the position of the lens too. So, you can start
out with the lens shifted hard left and you can run your sequence of
captures, shift it to the center, run your sequence of captures, and then
shift it to the right and run a final sequence of captures. Most of those
90 FoV lenses have an effective image circle as wide as 130 degrees.
It's still a lot of work, but if a person chooses to not use the more
efficient film technology and MUST shoot digital, then this is a viable
tool.
AG
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|