Basic Explanation Of Shift - Hasselblad HTS 1.5 User Manuals

HTS 1.5
Item no.: 3043400
TILT
Original scene
Fig. 4
Sharp
Sharp
Unsharp
Camera angle and lens movement
Fig. 1
In this diagram, a focus setting has been made for
the yellow object at distance A. This in turn produces
a specific 'lens to sensor' distance B.
The relationship between these two distances is
reciprocal; alter one and you must alter the other to
maintain sharp focus.
continued overleaf
Fig. 2
In this diagram, if distance C is now altered so that
the blue object is sharp, then distance D will be
altered accordingly. Likewise E and F.
Only millimeters of difference in distance are required
from lens to sensor to create great changes in subject
to lens focus distance and this is why tilt becomes a
possibility.
continued overleaf
Fig. 3
When tilting the lens, distance D is decreased, allow-
ing focus for the longer distance C. Similarly, F has
now increased allowing focus for the shorter distance
E. Consequently, the red object has the required sen-
sor to lens distance for correct focus and so has the
blue object, thereby allowing them to be both sharp at
the same focus setting without any need to alter the
aperture setting.
continued overleaf
5
In this diagram, the lens is focused on the yellow ob-
jects. At the widest aperture only the yellow objects are
covered by the depth of field.
This situation illustrates that producing sharpness in
certain parts of the subject can produce unsharpness
in other parts of the image.
Note that the vertical objects show a varying amount
of sharpness according to height as well, not only dis-
tance from the camera as might normally be expected.
You should be aware of this possibility occurring. In
this particular case, if the yellow objects were one solid
object, it might hide the unsharp section of the blue
object to produce apparent sharpness over the whole
image.
Sharp
Unsharp
Sharp
Sharp
Unsharp
Unsharp
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SHIFT
– a basic explanation
A classic problem in architectural work
and similar is the preservation of parallel
elements in the subject when the camera
angle has to be moved.
Shift also allows the creation of 'stitched'
panoramas.
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Inside the camera
A B

C
F
E D

C
F
D
E

Fig. 5
Unsharp

Basic explanation of shift

Shift
The image from the lens is focused and projected inside the
camera onto the sensor. Normally, this so called 'image circle'
is just large enough to cover the sensor. However, the integral
converter in the HTS 1.5 enlarges the image circle. This allows
parts of the image to be projected outside of the sensor area.
These parts would not normally be recorded but would neverthe-
less remain accessible.
If the lens is shifted, the projected image will consequently
move, allowing the previously unrecorded parts of the image to
project onto the sensor and thereby be recorded.
Shift
Tilting the camera upwards to include the top
of the blue object would make the parallels in
the yellow objects converge.
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USER MANUALS
Result
Fig. 1
Only the yellow objects are sharp
Fig. 2
Fig. 3
All the objects are now much sharper
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In this diagram, the lens is focused on the yellow
objects. At the widest aperture only the yellow
objects are covered by the depth of field.
When the lens is tilted, the plane of the depth of
field tilts. The left side of the blue object is now
sharp and the right side unsharp. The left yellow
object is unsharp while the right yellow object
remains sharp.
Note that in this case, as opposed to the previous
situation illustrated, the sharpness of each object
is not affected by its height.
Unsharp
Sharp
Sharp
Unsharp
Unsharp
Sharp
Unsharp
8
Shifting the lens allows the camera (image plane and lens
plane) to remain parallel to the subject. This prevents any paral-
lels in the subject from converging as would normally be the
case if the camera was just pointed upwards.
View of inside the camera
(In reality the projected image would be
inverted)
The enlarged image circle is projected onto the
sensor (represented by the grey rectangle).
In this case, part of the image lies outside the
sensor.
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HTS 1.5 – 3043400 – 2011 – v3
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