Canon 40D - EOS 40D DSLR, Service Manual

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Technical Information
9
1.6 Exposure control
１）Metering
⑴Metering sensor and metering modes
It is the same 35-zone metering sensor (Fig. 015) as in the
EOS 30D. The metering modes are evaluative, partial (approx.
9% of viewfinder area), spot (approx. 3.8% of viewfinder area),
and center-weighted average metering.
⑵Evaluative metering algorithm
Previously, during automatic AF point selection and AF
point-centered evaluative metering, there was a tendency
for slightly excessive compensation. The compensation is
now more loose so that the exposure is more consistent.
⑶E-TTL II autoexposure algorithm
This is the same one as the EOS-1D Mark III's E-TTL
II autoexposure algorithm. By optimizing the method
of using the lens distance information, the exposure
becomes more accurate for highly reflective subjects.
The ambient light is metered in the seleted metering
mode.
２）Exposure control
Same as the EOS 30D's exposure control system with eleven AE modes and manual mode.
３）Shutter
While based on the EOS 30D's shutter unit, the shutter is now more reliable with a
contactless switch instead of a contact switch for running the 1st and 2nd curtains. Shutter
durability is approx. 100,000 cycles, the same as the EOS 30D's shutter.
＊With a fully-charged BP-511A, a bulb exposure can be as long as about 2.5 hours.
４）ISO speed
See the "General Information".
1.7 Flash
１）Built-in flash
The flash unit is the same as the EOS 30D's. Guide No. 13.
If the built-in flash is fired rapidly in succession, the flash firing will be stopped to
prevent heat damage to the built-in flash cover and fresnel lens (diffuser).
＊ In the case of the EOS DIGITAL REBEL XTi/400D DIGITAL which has similar specifications, if the built-in flash is
fired 20 times successively at 10-sec. or shorter intervals, the firing will be stopped. With the EOS 40D, the flash
control is more minute so that the flash stoppage is less likely to occur than with the EOS DIGITAL REBEL XTi/
400D DIGITAL.
＊ Although the degree of heat from the built-in flash is the same as with the EOS 30D, the flash stoppage is provided
for product safety.
Fig. 015 Metering sensor
Fig. 016 Metering zones