Canon Camera Hackers Manual page 34

(Landscape, Sports, etc.), the camera will determine the optimal compro-
mise between those entities. In manual mode, most cameras allow you to
set a fixed ISO value ( Sv), and some cameras even allow you to select a fixed
shutter speed ( Tv) or a fixed aperture ( Av). In such cases, the camera can
easily derive the other values from the above formula.
Let's now take at look at the remaining parameters in the Miscellaneous
group and their abbreviations when displayed:
Value Hg
"Real" aperture
The true aperture, not rounded for display purposes.
"Real" ISO
The true sensor speed as used in the APEX formula.
"Market" ISO
The sensor speed as displayed by the native Canon firmware. This
value is rounded and approximately 1.6 times higher than the real
ISO value, probably for marketing purposes. Therefore, the nickname
Market ISO.
Set Exposure Ev
The effective Exposure Value computed from shutter speed and
aperture (Tv+Av).
Measured Ev
The Exposure Value computed from scene brightness and sensor
speed ( Bv+Sv).
Set Bv
The Brightness Value computed from shutter speed, aperture, and
sensor speed (Tv+Av-Sv).
Measured Bv
The measured scene brightness.
Overexp. Value
Shows an overexposure value computed from the APEX values:
Av+Tv—(Bv+Sv). This is without flash illumination.
Canon Overexp. Value
Shows an overexposure value computed by the native Canon
firmware. This is a rounded value.
Scene Luminance
Shows the scene brightness in Candelas per square meter.
The differences between set Ev and measured Ev, and between set Bv and
measured Bv, are usually small when the camera is in automatic mode.
However, if you use Overrides (section 4.3.1), the differences can be
4.2 Customizing the user interface
In Misc
Av
I-R
I-M
Evs
Evm
Bvs
Bvm
dE
dEc
B
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