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Note - Dynamic Menu
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Page layout altered, in order to use larger diagrams.
Aperture - Shutter
Relationships -
Here then is some diagramatic material to hopefully
better help you see the parallels and relationships
between apertures, shutter speeds (exposure time) and
focussing matters. It is probably best if you have already
read (plowed thru!!) the preceeding section just on
Photo facts
and then this section should help reinforce that information.
Parallels between shutter and aperture -
This first diagram attempts to show the parallel graphically
- the idea here being to equate halving or doubling
of exposures both with time and aperture. In other words
... if we move from the left with time, OR with
exposure, there is a halving. This diagram is not trying
to show an inter relation ... just a side-by-side comparison.
I am not sure this as clear as I originally intended
- if problematic then let me know. |
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Exposure equivalence
-
Now, we use much the same diagram but for a different
reason. Notice this time how as aperture sizes get smaller
(numerically bigger!) from left to right ..... we show
shutter speeds getting larger - longer.
Thus, on the left we show a combination this time, of
full aperture f1 and a short shutter speed of
1/000 second. At the other end far right we have
progressed through to the smallest aperture f32
but with a shutter speed of 1 second.
EVERY single position on this diagram is the
SAME exact exposure - in other words the amount
of light landing on film or CCD (charge couple device)
is identical. Relate this now to the choices you have
to make when taking photographs .... maybe go back to
Photo facts
and read again regarding depth of field and freezing
of movement.
With manual settings and using aperture or shutter priority
options - you have to manage to decide for a given exposure
where, along this set of combinations, you want to make
your choice, and know why. |
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Aperture vs Depth
of Field -
Finally, an attempt to further detail the relationship
between apertures and focus.
The top portion of this diagram in fact only repeats
what we have seen above .. as a reminder of the inverse
relationship between shutter speeds and apertures. Again,
on this - each position is showing the exact same exposure
but - youir choice of aperture is going to influence
just how ''deep'' is the depth of filed with close ups.
Look at the two diagrams lower left - they pretty much
tell it all - by showing two extremes. Consider once
more trying to photograph your snubbie from the muzzle
end ... but want cylinder and even grips to be passably
sharp.
The upper of the two shows a combination exposure of
1/000 second at f1 ... great for stopping
movenment and camera shake but ... extremely shallow
depth of field. All you might get sharp is muzzle and
foresight!
Now consider the lower one, where we go the other extreme
and use a 1 second exposure - at f32!
We see a considerable increase in the depth of field
(zone of sharpness) .. such that maybe we will not only
have the muzzle sharp but the cylinder also. Remember
- it will improve even more if you move back a bit and
then crop the picture later to use just the main subject.
Just to prove a point .... go look at actual pics
of snubby taken with different settings ....
it shows what is meant.
One more point is worth making - even with high quality
lenses, there can be problems at both extremes ... ''wide
open'' and ''stopped right down''. Now in fact f1
will not usually be found as such .. a ''fast'' lens
of 50mm say on a 35mm camera would be ''fast''at about
f1.4. Also, the majority of lenses do not stop
down much smaller than f22. Note however, that
lens aberations are most likely to show when wide open
.... so a shot taken at f1.4 could display some
loss of picture edge definition. At the other extreme
too, fully closed down, there can also sometimes be
problems with certain lighting conditions. If possible
try and use in-between stops as much as practicable. |
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| Well - this has been
heavy going eh?! I can only hope that something of what
you have seen makes enough sense to help make things
a bit clearer. As mentioned elsewhere, some reading
of books or web browsing will quickly help you capitalize
on this but hopefully it has been enough to fill in
a few blanks. |
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