Canon Camera Hackers Manual page 65

56
C H A P T E R 4 Teach Your Camera New Tricks
TV Bracketing Value. This entry is used for modifying the exposure time
f
during a series. A value of 2 results in an exposure time multiplication
factor of 2
speed series of 1/100, 1/25, 1/400, 1/6, 1/1600, and so on. This type of
bracketing is typically used for HDR work (section 4.6.2). It can also be
used for getting the perfect exposure when AV bracketing is not avail-
able.
AV Bracketing Value. This entry allows you to modify the aperture for
f
the individual shots in a series. For example, if you set the value to one
f-stop and the aperture to 5.6, you will end up with a series shot at ap-
ertures 5.6, 4.0, 8.0, 2.8, 11, etc. AV bracketing is not suited for HDR
work because the depth of field changes with each aperture change;
but it's a good option for getting a perfectly exposed single image. This
menu entry is only available on cameras with a diaphragm.
Subj.Dist.Bracket Value. This entry is used for focus stacking, which is
f
discussed in the next section.
ISO Bracketing Value. This entry allows you to modify the ISO value. The
f
subentry Value Factor specifies a factor that is multiplied with the ISO
Bracketing Value—just to save you a few hundred keystrokes. The result
is added and subtracted from the original ISO value. For example, if you
start with an ISO value of 100, an ISO Bracketing Value of 2, and a Value
Factor of 10, you will end up with a series of 100, 120, 80, 140, 60, etc.
ISO bracketing is well suited for classical exposure bracketing when you
need the perfectly exposed single image, especially if AV bracketing is
not available. It is not as well suited for HDR work (see above) because
the signal-to- noise ratio changes with each ISO setting.
Bracketing Type. There are three bracketing types. Choosing "+/–" will
f
result in a series with alternating over- and underexposed images, typi-
cally used for finding the perfect exposure and for HDR work. The op-
tion "–" will result in a series of increasingly underexposed images.
Finally, the option "+" will result in a series of increasingly overexposed
images. The last two options are often used for focus stacking.
Clear Bracket Value on Start. If this option is enabled, the bracketing
f
values will be reset to default when the camera is powered up.
Add RAW Suffix. When this option is enabled and you shoot RAW
f
images, a suffix is added to the names of the resulting RAW files, for
example, IMG_2041_01.DNG, IMG_2041_02.DNG, IMG_2041_03.DNG. This
allows you to easily identify the bracketing series later. However, in the
CHDK file browser of DryOS cameras (section 2.2), the files will show up
as IMG_20~1.DNG, IMG_20~2.DNG, IMG_20~3.DNG, because the file browser
is limited to 8.3
6 At most, eight characters in front of the dot, three behind it.
2
= 4. So, if you start with 1/100 sec, you will get a shutter
6
filenames on this platform.