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6.2 HDR Panoramas
201
In section 4.6.2 we already discussed how to create an HDR series with
the help of the CHDK. Basically, you can use the same technique for each
single image of the panorama:
f
First, go to
ALT
>
MENU
>
Extra Photo Operations
and select
Off
for
Disable Overrides
.
f
Then go to
ALT
>
MENU
>
Extra Photo Operations
>
Bracketing in Continu-
ous Mode
and dial in a
TV Bracketing Value.
For normal bracketing work,
a good value is
2 Ev
, but for panorama work a bit less will make the
registration of images easier. As
Bracketing type
choose
+/–
, a typical
set-up for HDR stacks.
f
Finally, switch the camera’s shooting mode to
Custom Timer
and config-
ure the timer with a
delay
of
0
sec and the number of
shots
set to
3
or
5
,
depending on the contrast in the scene.
f
Now, when you press the shutter button, you should get one correctly
exposed picture, one overexposed picture, one underexposed picture,
and so on.
After you set up the camera in this way, you can take the images for the
panorama (don’t forget to set a fixed ISO value and a fixed white balance).
Press the shutter button, wait for the images to be taken, turn the camera,
press the shutter button again, etc. A tripod is recommended but not abso-
lutely necessary. Make sure to use fresh batteries and a memory card with
enough free space.
Let’s assume that the focal length of your camera lens is equivalent to
35mm at a wide-angle setting. If you’re using the camera in portrait mode
with an overlap of one third between each panorama part, you can cover
an angle of view of approximately 25 degrees. For a single row panorama,
this would result in 15 parts of three images each, or 45 total images. Even
if you shoot JPEG, you would end up with approximately 120 MB. Shooting
RAW would fill your memory card with approximately 450 MB! Multiple
row panoramas, such as those required for 360° spheres, take a multiple of
that value.
Combining the image series into one HDR panorama can be performed
with a suitable panorama stitcher.
Autopano Pro, PtGui Pro,
and
Hugin
can
all compose HDR panoramas. The output can be saved in an HDR file format
such as
OpenEXR
or
HDR Radiance
. The resulting file can then be tone
mapped using an HDR composer (e.g.,
Picturenaut, Photomatix Pro, FDRTools
Advanced,
or
Dynamic Photo HDR
) to produce printable HDR output.
Example project
The following image (
Figure 6-1
) demonstrates the use of panorama tech-
niques to solve a problem often encountered by owners of compact
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