Canon TL - Aperture Control

Index
Preset
Aperture
Incoming light and depth - of - field are adjusted by turning
the preset aperture ring to the desired f/stop_
• As
the f/ stop value gets larger, the amount of light
reaching the film plane becomes correspondingly less_
For each f/
stop up, the light is reduced one- half _ Accord-
ingly , when the aperture is increased by one f/ stop, the
ex posure is doubled , and when it is increased by two
f/ stops the exposure is quadrupled _
•
Certain lenses, however, have no relation to the light-
ness being halved between the ma x imum and the next
f/ stops on the preset aperture ring _
•
The preset aperture ring can also be set between two
f/stops_
•
The ratio between the aperture and the amount of
exposure , using f/2 as the basis , is as follows :
f/
stop :
1.2 1.4 1.8 2 2 _8 3 _5 4 5_6 8 11 16 22
Exposure Ratio :
3 2 1.25 1 1/2 1/3 1/4 1/8 1/ 16 1/ 32 1/ 64 1/ 128
Presetting Aperture and Checking Depth-of-
Field
Lens with A-M Ring
1
Presetting of Aperture: Set the A-M ring at " A"_
Then set the desired f/ stop on the pre - set ape r ture
ri ng to the index_ The diaphragm will close down to the
preset f/ stop only for the instant that the shutter is re-
leased_
Except for that instant , the diaphragm remains
fully open_
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