Hands and Fingers

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 Phaseof 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.

In the Capture Phaseof operation a very different set of ergonomic imperatives prevails. Now the operator is looking at the subject through the viewfinder and must carry out all control operations by feel.  In this situation the principal type of  interface module which can be reliably operated by the left hand is

* 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 fingerof 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.

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 8shows 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.