The late models of the
Leica M camera line are often criticized for not offering autofocusing. It is certainly correct that a line of
autofocus lenses would eliminate any of those criticisms. But is the lack of autofocus really such a
hindrance?
With the advent of
autofocus one little trick to speed up focusing of our cameras has all but been
forgotten. I am talking about
hyperfocal lens settings with the help
of a depth of field scale. Most lenses
available today no longer have depth of field scales and thus make focusing via
hyperfocal settings impossible.
Fortunately, most Leica lenses till offer this advantage and its
application can overcome the lack of autofocus to quite an extend.
A lens can only be
accurately focused at one certain distance. Everything before and after that point of
focus is effectively out of focus. Yet
we all know that the pictures we take show scenes and subjects to be sharply in
focus over a considerable distance. Are
our books of physics wrong? Not at
all. The reason for this apparent
contradiction is our eyes. Fortunately
they aren't good enough to recognize out of focus areas in our pictures unless
they reach a certain level.
Imagine photographing a
small point. When not properly in focus,
this point will become larger and show up as a fuzzy disc. This disc has to be of a certain size before
our eyes recognize it as out of focus.
This representation of a point is referred to as the circle of
confusion.
In these days of virtually
everything being auto focus we rarely pay any attention to focusing
anymore. As a matter of fact, many
outsiders consider the Leica M rangefinder cameras with their manually focusing
lenses an anachronism. Yet in quite a
variety of situations these lenses can be focused as fast or faster than any
auto focus system.
That is because the vast
majority of the Leica M lenses are non-zoom lenses. That is the reason why to this day all of
them have a depth of field scale. Many
photographers and picture takers have no idea what a depth of field scale is,
and if they do, they rarely know what to with one.
It is a known fact that
the aperture setting on our lenses, the f-stop used to take a picture,
determines how much of what we photograph will be in focus, how much depth of
field there will be. The smaller the
aperture, the more depth of field. That
is what a depth of field scale is all about.
It will show the distance from the point closest to the camera to the
point furthest from the camera that will be in focus.
Increase of depth of field
by decreasing aperture size
Effectively one third of
the total depth of field will be in front of the point of focus and two thirds
will be beyond it. If applied correctly,
this can actually greatly improve the sharpness of our photographs. Imagine taking a picture of a mountain
scene. The mountains are obviously far
enough away to constitute infinity as far as the focus settings on our lenses
are concerned. Subsequently it seems to
make sense to set our lenses to infinity to make sure the mountains are in
focus. As a matter of fact, if we use
the rangefinder on a Leica, this is exactly what will happen.
However, let’s remember
the above rule which states that two third of the depth of field is beyond the
point of focus. That means in our mountain
scene, two thirds of the depth of field will be wasted. The depth of field scale will help to prevent
that, if properly applied.
Our exposure settings will
always be a combination of shutter speed and aperture. Once we or the camera determine the correct
exposure settings, we will know what aperture the picture will be taken
with. Back to our mountain scene. Instead of setting the infinity mark opposite
the focus mark on the lens, all that needs to be done is to set the infinity
mark opposite the marking of the aperture we are using. That will still give proper focus to
infinity, but it will greatly increase sharpness in the areas closer to the
camera as indicated by the other aperture mark on the depth of field scale.
Above focused on the background
Below focused on the
foreground
Focused at hyperfocal
setting with one third in focus in front of the point of focusand two thirds
behind the point of focus
Picture examples form
"Kleines Leica Buch (Little Leica Book), 1952 edition
In this example, the boy flying his kite is
obviously the main subject and therefore
should be in focus.
However, focusing on him would most likely render the
background out of focus.
Utilizing the depth of field scale assured that all is in focus.
It is a fact that the
smaller the aperture, the more depth of field we will have. But we shouldn’t indiscriminately use the
smallest aperture all the time, because this can easily lead to the necessity
of too slow a shutter speed which in turn can lead to blurry pictures because
of camera movement.
As I explained above, the
circle of confusion determines what detail in our pictures appears in focus and
which not. Unfortunately, the size of
the circle of confusion must also be based on a certain picture size. In most cases that is an approximate
enlargement of five times or a 5 x 7 inch enlargement from a 35mm negative or
full frame digital sensor. With other
words, up to a 5 x 7 inch size enlargement our pictures will display maximum
sharpness and maximum depth of field.
But what about enlargement
greater than a 5 x 7 or if considerable cropping is necessary? Does that mean the depth of field scale on
our lenses is useless? Not at all. All we need to do is use the depth of field
settings on the lens with an aperture one or two stops larger than the
aperture in actual use. With
enlargements of 8 x 10 or 11 x 14, the next larger aperture will usually be
sufficient. If the enlargement size is
greater than that, use a two stop larger aperture.
Why do all of this instead
of just using the rangefinder and focus on our main subject? Because you can greatly increase your speed
of operating the camera. Using the depth
of field scale and setting the lens as explained above, this is called
hyperfocal setting, will eliminate the need to focus altogether and thus make
the operational speed of your camera that much greater.
The above figures are
based on 35mm size negatives or full frame digital sensors. Larger or smaller negative and sensor sizes
will lead to different depth of field.
Different focal lengths of our lenses will do the same. In general, the shorter the focal length the
more depth of field there will be. This,
however, is nothing to worry about because the depth of field scales will reflect
that.
Give it a try. You might very well find that your pictures
in some cases will display a greater range of sharpness and you will be able to
use your camera a lot quicker. It might
very well be the difference of being able to catch a great moment on film or
memory card instead of losing it to your camera being too slow.
________________________________________________________________________________________
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Isn't this kind of awkward?
ReplyDeleteIsn't this a rather outdated approach and primarily an excuse for the lack of autofocus?
ReplyDeleteBut wouldn't the addition of autofocus elevate the Leica M cameras even further? After all, you have written about this being the one thing that is missing when comparing the M cameras to the competition.
DeleteOf course it would. But we must not overestimate the importance of autofocus. This article was meant to show that perceived lack of fast focusing with non-autofocus lenses can easily be overcome by applying hyperfocal settings.
Delete