Canon A-1 Repair Manual page 26

the lens used in shutter priority AE mode.
In Programmed AE, there is a case when the camera may
warn of overexposure at the shutter speed/aperture
combination for EV 18 (1/1000 sec./f/16).
This may not seem logical, as EV 18 is within the
meter coupling range allowed for the camera. The
reason for this is that the 1/1000 f/16 combination
is supposed to be indicated in the viewfinder displays
at exposure values up to EV 18 + 3/8.
However, since
the shutter speed indication of 1/1000 sec. is the
fastest possible data in the viewfinder, the camera
is made to indicate the overexposure flashing warning
when the exposure requires a shutter speed faster
than 1/1000 sec. Please refer to the following table
for more details:
EV
Computation Value
Display
Indication
18 1/1000
16
1000
16
.....
,.-
I . " ,'
18
+
1/8
1/1000
+
1/8
16
: 1000 : , 16 ~
" ....... ,...
,
"
. .
,
''''.,
.'
~,
18
+
2/8 1/1000
+
1/8
16
+
1/8
aooo ;
, 16 ,
",~,. "
,,'
,,,-n,.,
" H
18
+
3/8 1/1000
+
2/8
16
+
1/8
, 1000 :
' 16 :
"IV. "
I, I,
••• " . , • I
.
'"
18
+
4/ 8
1/1000
+
2/8
16
+
2/8
- 1000 '
;16 "
.
,
".,1\ "
""
Accordingly, notice that when you are in programmed
AE mode the viewfinder display flashing means that the
camera is outside the exposure coupling range of EV 18.
While the self-timer is in operation or the shutter is
open, the display goes out.
When an FD lens is used, full aperture metering and
stopped-down metering may not have exactly the same
display indication. This is because the shutter
speed and aperture indication is displayed at every
0.5 step depending on such factors as the maximum
aperture correction and f-number tolerances, linearity
of the metering system. But, this poses no problem
in actual exposure determination.
If the shutter button is pressed down in one quick
stroke, the viewfinder display may not come on. (If
the shutter button is held in the depressed position,
the viewfinder display will become visible after the