Canon EOS 250D Advanced User's Manual page 153

Aperture Value Display
The higher the f/number, the smaller the aperture opening will be. The f/
z
number displayed will differ depending on the lens. If no lens is attached to
the camera, "00" will be displayed for the aperture.
Shooting Tips
When using an aperture with a high f/number or shooting in low
z
light scenes, note that camera shake can occur.
A higher aperture f/number will make the shutter speed slower. Under
low light, the shutter speed can be as long as 30 sec. In such cases,
increase the ISO speed and hold the camera steady or use a tripod.
The depth of field will vary depending not only on the aperture, but
z
also on the lens and on the subject distance.
Since wide-angle lenses have a wide depth of field (range of
acceptable focus in front of and behind the point of focus), you need
not set a high aperture f/number to obtain a sharp picture from the
foreground to the background. On the other hand, a telephoto lens has
a narrow depth of field.
And the closer the subject, the narrower the depth of field. A farther
subject will have a wider depth of field.
Set the aperture so that the shutter speed display does not blink.
z
If you press the shutter button halfway and change the
aperture with the shutter speed displayed, the shutter
speed will also change to maintain the same exposure
(amount of light reaching the image sensor). In this
operation, if the shutter speed exceeds the adjustable
range, it will blink to indicate that the standard
exposure cannot be obtained.
If the picture will be too dark, the "30"" (30 sec.) shutter speed display
will blink. If this happens, turn the <6> dial counterclockwise to set a
lower f/number or increase the ISO speed.
If the picture will be too bright, the "4000" (1/4000 sec.) shutter speed
display will blink. If this happens, turn the <6> dial clockwise to set a
higher f/number or decrease the ISO speed.
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