CAMERA ERGONOMICS
Part 6, Hands and Fingers
Author AndrewS
Introduction In Part 4 of this series I explored the
functional anatomy of the hand. The vast majority of cameras are hand held
devices. Clearly therefore, the manner
in which the hands and fingers interact with the camera is of critical
ergonomic importance especially in the Capture Phase.
Left Hand On cameras with interchangeable lenses and most super zoom
types, the left hand has two main duties. It must support the weight of the
lens and sometimes, when the right hand is busy adjusting things, most of the weight of the camera body as well.
Part of this supportive role is to hold the camera/lens unit steady to prevent
blurred photos.
The second main duty is to operate controls, while maintaining the support role. From the days of all manual, film based
photography, traditional controls allocated to the left hand were manual focus
and aperture setting. With the advent of zoom lenses, operating the zoom action
was added. In the electronic era,
controlling lens aperture is usually carried out by the right hand. Indeed, there is no technical reason why the
left hand needs to control any function of an electronic camera or lens, given
the availability of power zoom and powered manual focus.
However in the interests of dividing labour between the
hands it can be desirable to allocate some controls to the left hand. Let us
consider what kinds of actions the left hand can perform.
In the Prepare Phase
of camera operation the left hand does not have to support the lens/camera
unit, except in a very general fashion so as to prevent it falling on the
ground. In this phase the left hand can reach and operate a variety of
interface module types. These include
* On the lens or the left side of the camera body: Switches,
dials, buttons and levers.
These can be used to make settings in the several minutes
prior to capture, at a time when the operator is not looking through the
viewfinder and can therefore look directly at each control module.
* Rings/collars around the lens barrel.
If these are positioned, sized and shaped properly, they are
easy to locate and operate by feel with the camera in landscape or portrait
orientation. They need to be positioned so the left hand can continue it's
support role while working the rings.
Left hand capture phase controls, including primary and
secondary exposure and focussing controls should never be allocated to the kinds
of interface modules (buttons, dials, levers, switches) suitable for Prepare
Phase tasks.
Why? Because the left
hand cannot be in two places at the same time. Either it is holding and
supporting the lens barrel or it is pressing a button on the left side of the
camera or somewhere on the lens.
Some camera makers locate buttons for ISO and/or AF (the
button which allows active AF position to be moved) on the left side of the
camera body. ISO is a primary exposure variable. AF position is a secondary focussing
variable. Both belong in the Capture Phase of camera operation. With such a
camera, if you want to change ISO or shift AF position, you must stop the
capture process, drop the camera down from the eye, remove the left hand from
the lens, press a button, return the left hand to the lens, then make the
adjustment with the right hand. During this tedious process, any mobile subject
will have left the field of view. Forget about capturing critical moments.
Note that levers or buttons on the lens barrel may seem easy
enough to find with the camera in landscape orientation, but will be
unreachable when the camera is flipped over to portrait orientation.
In an electronic camera just about any function could be
allocated to lens rings. Newcomers to
photography might not have any preconceived expectations about this but old
timers will be looking to find controls for manual focus and zoom located on
the lens barrel.
Example: Lens barrel
interface module location and type
 |
| Photo 1 |
Photo 1, Lens Barrel
Good Design. The maker of this lens
appears to have a good understanding of the distinction between Pepare and
Capture Phases of operation, leading to an ergonomically appropriate choice of correctly
located interface module types. Thus we
see large, ribbed, rubberised rings for Zoom and Manual Focus, both required in
Capture Phase. These modules are easy to find and operate by feel, using
landscape or portrait camera orientation. You can also see the Set and
See sliders for Focus Range, AF/MF, Stabiliser On/Off, Stabiliser Mode 1/2.
These four parameters require adjustment in the Prepare Phase when it is quite
appropriate to drop the camera down from the eye to look at the sliders and
adjust them.
 |
| Photo 3 Find and press the iFn button |
 |
| Photo 2 Basic hold |
 |
| Photo 4 Find and rotate the focus ring |
Photos 2, 3, 4, 5 Lens
barrel iFunction. The maker of this lens encourages users to adjust
Aperture, Shutter Speed, Program Shift, Exposure Compensation, White Balance,
ISO and other parameters by pressing a button labelled iFn on the lens barrel to
activate the feature then rotating the focus ring to make the adjustment. Most
of these parameters require adjustment in the Capture Phase of operation. This
camera provides ergonomically simple and direct means of adjusting each of
these parameters on the camera body so the reasoning behind the iFn concept is
a mystery to me. Perhaps the marketing department wanted a unique selling
proposition, I don't know.
Photo 2 shows the
basic camera/ lens hold position. To adjust any parameter you must first find
the iFn button on the side of the lens (Photo 3) which is not easy as it is not prominent and
not located near a finger with normal hold in use. Then you must press the iFn
button repeatedly until the required parameter is displayed in the viewfinder,
at which point the cognate parameters normally displayed in the EVF such as shutter speed, ISO etc are
overlaid by the iFn graphics and therefore invisible. So if you adjust Aperture,
the effect of doing so on the Shutter Speed is not seen. Then the fingers of
your left hand have to shuffle towards the front of the lens searching for the
focus ring. (Photo 4) This is then rotated to change the selected
parameter and the change confirmed with a half press of the shutter button.
 |
| Photo 5 Portrait hold, iFn button inaccessible |
When you turn the camera 90 degrees for
portrait framing (Photo 5) the iFn
button disappears beneath the left hand and is virtually inaccessible.
A straightforward time and motion study shows that the process
of making any adjustment via the iFn button is much slower, requires more
module activations and requires more finger stretches than the same adjustment
on the camera body. It's a kludge, but
some users report that they "like" it.
It appears the maker and some users of this equipment have
yet to reach a clear understanding about what types of interface module work best in
the different Phases of camera operation.
Right Hand Like the left hand, the right hand has two main duties,
holding/supporting the camera and operating the controls. Each finger of the right hand has a specific functional
capability which defines it's optimum role.
The index finger
of the right hand is uniquely qualified for some of the most critical tasks in
the capture phase of operation. It is
for most people on the dominant side, it has excellent touch and position sense
and it does not have to grip the camera. For these reasons it is almost
universally tasked with pressing the standard two stage shutter button. In addition
it can efficiently control primary and secondary exposure and focussing
variables. Referring back to Part 4, the index finger can, by touch,
without having to look at the finger, efficiently control four user interface
modules, provided they are correctly located.
Consider the outcome of allocating the following items to
these four modules:
1. Shutter button (on half press, activates auto focus
and auto exposure metering, on full
press makes exposure)
2. Top front main control dial (function depends on Shooting
Mode)
3. ISO button (press
to activate, change with control dial, confirm with half shutter press)
4. Exposure Compensation button (press to activate, change
with control dial, confirm with half shutter press)
Let us give this camera a rapid means of switching exposure
modes, for instance a Set and See shooting mode dial sited on top of the camera
where it can be seen at a glance.
Now the user can quickly, by feel, without looking at any of
the physical controls, without shifting grip with the right or left hand and while viewing the subject continuously
through the viewfinder, carry out the
following tasks:
* Adjust shutter speed, aperture or program shift (depending
on which shooting mode is set).
* Adjust ISO.
* Set exposure
compensation
* Start/Lock
autoexposure
* Start/Lock autofocus
* Make the exposure
The thumb of the
right hand has two tasks, gripping the camera and operating controls. It has to
do both these tasks simultaneously making for a conceptually difficult design
brief.
Let us examine gripping first. everal design features must be in place for the thumb to be
able to grip the camera in a relaxed but secure fashion. This will be possible
when the right hand in basic camera hold position is able to adopt the "half
closed relaxed" posture described in Part 4. This requires:
* Enough width between the right side (as viewed by the
user) of the monitor screen and the right edge of the camera body. There is no
magic number but 50-55 mm combined with good contour design is about right. Some
cameras manage decently well with only 40 mm.
* A carefully shaped, sized and angled thumb rest on the
right upper part of the camera back. This must be contoured anatomically so the
camera fits the user, not the other way around.
* An indented area clear of any control modules or
intrusions on which the ball of the right thumb can comfortably rest in the
basic grip position. This is located immediately to the left of the thumb rest
and needs to be of sufficient size to accommodate even large thumbs without
inadvertently activating a control module.
Now let us turn to operating.
Referring back to Part 4, there are, in the functional
sense, basically two actions which the
thumb can carry out.
First are actions
which maintain opposition of the thumb metacarpal and therefore grip. A small amount of side to side movement at
the carpometacarpal joint will not unduly interfere with opposition. It is also
possible for the thumb to make limited flexion movement at the interphalangeal
and carpometacarpal joints without unduly disrupting opposition.
Putting these two actions together in the Capture Phase of operation,
it becomes reasonable to ask the thumb
to operate one user interface module immediately to the right of the rest
position and one immediately to the left.
These modules could be assigned any of the tasks required in the Capture Phase of operation, but I propose an ergonomically consistent
approach. The logic of this is similar
to the way motor car controls are laid out. It would be perfectly possible for
a motor car to be steered with the feet, which would shift power control and
braking to the hands. But such a car would cause instant carnage on and
anywhere near the roads because people would not be familiar with it's
ergonomics. I presume nobody will die as
a result of confusing camera design but inconsistent control layout between one
camera and the next makes the process of taking photos less enjoyable and
results in missed moments.
So the approach which I propose is to allocate exposure
tasks to the index finger and focussing tasks to the thumb.
In this allocation of tasks the index finger would function
as described above.
The thumb would have two duties to perform in the Capture
Phase of operation. These are
* Start/lock autofocus (a primary focussing control) [or
video in Movie Mode] with a button immediately to the right of the thumb at rest
position and activated by moving or rolling the thumb about 5 mm to the right. Allocation of start/lock AF to half press
shutter button would be possible for users who prefer to operate that way.
* Move position of active AF area (a secondary focussing
control) with a JOG type module immediately to the left of the thumb at rest
position. This can be pressed in and also moved in any direction up, down left
or right.
Note that in modes of camera operation other than still
capture (Menu scrolling, Movie, Image review) the JOG module would perform
different tasks.
Next we come to actions of the thumb which require undoing opposition of the metacarpal and therefore
releasing secure grip on the camera with the right hand. This in turn means
that while these actions are being carried out the left hand has to support the
camera.
Consider the layout of a camera. On the right side there is
an area bounded by the monitor, top,
bottom and right side of the camera body. I call this the "control
panel". We have thus far been
considering actions occurring at the top of the control panel. Now we consider
actions requiring the thumb to move down to the middle and lower parts of the
control panel. This movement of the thumb forces the metacarpal and in some
cases the whole palm of the hand away from the camera.
In consequence, Capture Phase actions should not be
allocated to the middle and lower zones of the control panel. This is the place
for Prepare and Review Phase actions.
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| Photo 6 DSLR Basic Hold |
This is illustrated in Photos 6, 7 and 8. Photo
6 shows a DSLR in basic right hand hold. This camera has a well designed
handle and thumbrest for a comfortable and secure basic hold. However shifting
AF area position is allocated to the 4 way controller low down on the control
panel. Photo 7 shows that to change AF area position (a
Capture Phase task) the right hand has to be completely removed from it's
secure grip, requiring the left hand to take on all camera support duty.
 |
| Photo 7 Shift Active AF Area |
There is a much better way. Photo 7 also shows a white X in a white
rectangle just above the Menu button. If
a JOG lever were to be placed at the white X, it could be tasked to directly
shift AF area position. Photo 8
shows the right hand position with the thumb directly over the white X. The JOG lever needs to be precisely located in
three dimensions so the thumb can operate it without flexing at the
interphalangeal or metacarpophalangeal joints, either of which would disrupt
grip integrity. Please refer to Part 4 for more discussion about this.
 |
| Photo 8 Shift AF Area with JOG Lever |
You can
immediately see that shifting AF position this way would be much faster and
smoother than the method actually provided by the manufacturer. The Movie and
Menu buttons can be shifted to accommodate the new JOG lever. The Menu button
is inappropriately placed in a high real estate value location anyway. It is
used for Setup Phase tasks, so it can be placed in a low value real estate location, such as
the left side of the viewfinder.
Last but by no means least, we come to the middle, ring and little fingers. These
generally operate together as grippers. An anatomically shaped and positioned handle
on the front of the camera is essential for proper grip. This is such an
important topic I have given it the whole of Section 7.
These middle and ring fingers can also have a limited role
as controllers. It may be possible with some camera layouts to locate a button near the right (as viewed by
the user) lower quadrant of the lens mount on the front of the camera. This
could be easily accessed by either the middle or ring finger and used for a
Prepare Phase action.
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