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| This is Mockup #13 showing optimal location of front and rear control dials with adjacent control modules. The author's hand is in the 'half closed relaxed' position with index finger on the shutter button. |
This post is about Mode Dependent Control Dials. These are dials without inscription. Their function depends on the currently set capture mode. I will call them Control Dials in this post.
In Capture Phase of use they are second only to the shutter button in the hierarchy of UIMs (User Interface Modules). Therefore all aspects of their design are of the utmost importance to camera operation.
They change primary exposure parameters in Capture Phase and can be used for scrolling in Setup and Review phases.
They are distinguished from Set and See dials which are inscribed with various settings. The function of set and see dials is always the same and the current setting can be seen by looking at the outside of the camera (you don’t have to look in the viewfinder or at the monitor). Their settings can be seen even if the camera is switched off.
Set and see dials are most useful for Prepare Phase actions, especially changing main capture mode, focus mode and drive mode.
Traditional-vs-Modern Control Systems This post refers to modern control systems based on the [Mode Dial + Control Dial(s)] configuration. Several modern cameras use some variant or hybrid of the traditional system based on the [Aperture Ring + Shutter Speed Dial + Exposure Compensation Dial] configuration. I have extensively analysed, compared and reported elsewhere on this blog the ergonomic effectiveness of the two systems and concluded that a well implemented modern system (many are not well implemented) is decisively superior.
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| Panasonic GH1. The G1 has the same front dial location. This is how not to do it. When holding the camera the upper part of the third finger of the right hand wraps around the control dial preventing access to it by the index finger. in order to work the dial the right hand must release its hold on the camera and shift position to work the dial, then shift back again to work the shutter button. |
Haptics This post is mostly about the location and configuration of control dials but that is not to neglect the huge importance of haptic issues in dial design. Control dials need to be easy for the operating finger(s) to reach and operate yet not be subject to unwanted operation, for instance by being bumped while carrying out some other action.
Serrations on the dials need to be sharpish and ‘grippy’ for the operating finger(s).
Dials need to stand proud from the adjacent body sufficient for easy operation without excessive risk of inadvertent movement.
The required amount of turning force on the dial needs to be carefully calibrated to the finger(s) which are intended to operate it.
I have owned and used cameras the dial(s) of which were so difficult to operate that I had to wonder if the maker had ever tried a working mockup prior to production.
Worst was the Panasonic G3, the rear dial of which was almost completely buried in the body. To operate the dial the user had to pull the right hand away from the body of the camera, sharply flex the thumb so as to apply the tip of the thumb just below the nail onto the dial in order to turn it. It was nigh on unusable.
The good news is that Panasonic’s designers are learning. The GH3/4 and FZ1000 have excellent rear dials.
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| Photo courtesy of Digital Photography Review Nikon 750D. Another front dial in front of and below the shutter button. This one is easier to reach than that on the GH1 above but the index finger and middle finger are quite separated, restricting access to the buttons behind the shutter button unless the right hand shifts grip. Shutter button and control dial are not at the same level and their finger press axes are about 60 degrees apart. In addition the dial is almost flush with its surrounds having minimal exposure for gripping. |
The left hand and fingers There are eight ways by which the left hand and fingers might interact with the camera/lens. These are defined by
* Eye level vs monitor viewing
* Landscape vs portrait orientation
* Over lens vs under lens left hand position
(2x2x2=8)
This means the left hand/fingers could come in contact with and interact with the lens anywhere around its circumference.
In consequence left hand controls for Capture Phase operation must be circumferential rings around the lens with lands or serrations all the way around.
It is not feasible for the left hand to operate control dials in Capture Phase. It can operate various levers, switches, buttons etc on the body or lens in Prepare Phase when the user can drop the camera down from the eye.
On the other hand (literally) the right hand/fingers are, or optimally should be, always in the same place in relation to the camera parts.
Therefore I have and most camera makers also have allocated control dials to operation by the index finger and thumb of the right hand.
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| Photo courtesy of Digital Photography review Sony A7. Here is another front dial in a very awkward place in front of the shutter button. The shutter button occupies the suboptimal top/rear position. The handle forces the index and third fingers apart. The control dial is a long way below the level of the shutter button. The finger press axis of the dial is at 90 degrees to the shutter button. Fortunately Sony completely changed and improved the handle and control dial design with the Mk 2 version. |
Throughout this discourse I assume the camera will have an ‘Auto’ mode for snapshooters who do not care to be bothered by all this business of control dials.
A study of functional anatomy forms the basis of my work on control dials and their operation.
The right index finger is the only one of the ten fingers which has exclusively operator duties with no gripper duty. Starting from the optimal ‘half closed relaxed’ position of the hand/fingers, it can flex by movement of the interphalangeal joints about 30mm and can move side to side at the metacarpo-phalangeal joint about 20mm.
Obviously the actual amount of possible movement depends on the flexibility of each individual’s joints and the presence of arthritis or other sources of restricted movement. But the figures given above are a working guide for design considerations.
The right thumb has to undertake both gripper and operator duties.
The primary gripper function of the thumb is achieved by a movement called ‘opposition’. This allows the tip of the thumb to touch the ends of each of the other fingers and is enabled by rotation at the carpo-metacarpal joint. Opposition allows humans to hold a camera and of course, many other things.
Without unduly disrupting opposition the thumb can, while continuing to hold the camera, move side to side, about 25mm each way, at the metacarpo-phalangeal joint and can flex at the interphalangeal joint.
These possible movements of the index finger and thumb have guided my search for the optimal location and configuration of control dials.
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| Photo courtesy of Digital Photography Review Olympus EM1 showing front control dial concentric with the shutter button. This is a workable arrangement particularly if as here, the pressing axis of the dial is only at 45 degrees to the pressing axis of the shutter button. Other models from Olympus have the control dial serrations vertical which is a less ergonomic arrangement as it makes the index finger press the dial at 90 degrees to the shutter button. If this handle was of more inverted L shape and the shutter button over to the left, the designers could have fitted another button to the right of the shutter button providing shutter button, control dial and three other buttons all easily accessible to the index finger. |
If you look at the actual positions of front and rear control dials on various cameras you might be excused for thinking that ‘anything goes’, with dials scattered about like confetti at a wedding.
The fact that users manage to make some of these creations work is a testament to human dexterity not laissez-faire design. In many cases users make cameras work despite bad design, not because of good design.
In the case of a single dial camera should the dial be located in front, for the index finger to operate, or at the rear, for the thumb to operate ? Perusal of existing cameras reveals there is no industry consensus about this at all.
Even within the model line up of most manufacturers, there is no consistent approach.
Yet the answer is perfectly obvious when the question is analysed ergonomically.
The index finger is the only one without gripper duty and it has the greatest range of free movement provided an optimal handle design is utilised, as described in my previous post.
So a single control dial is optimally located for operation by the index finger.
Note: Some commentators, bloggers and respondents to my posts and apparently some manufacturers (based on their actual products) take the view that the thumb should optimally operate the control dial while the index finger is poised over the shutter button ready to capture the picture.
But that is brain logic.
Ergonomics requires finger logic which says that shutter button and the control dial always operate sequentially, never simultaneously. So if they are located close together (not too close) and correctly designed we have the ideal configuration.
Next question: Is there a ‘best’ position and if so where ?
Review of actual cameras shows control dials in three main locations in relation to the shutter button:
1. In front of, high/low
2. Concentric with
3. Behind, near/far
Please refer to the photos for examples of these dispositions.
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| Photo courtesy of Digital Photograpy Review Canon EOS 70D. This is the standard Canon DSLR layout which has been in use for many years. The control dial could with advantage be closer to the shutter button and angled to match the line of the index finger. The line of near identical buttons behind the dial could be rationalised and moved closer to the shutter button for better access. Canon could easily improve this layout but they keep churning out the same thing model after model. |
Guiding principles
1. The right hand and fingers should be most comfortable and relaxed in the position in which they spend most time in Capture Phase. That is with the index finger on the shutter button. When I make mockups I put the shutter button where my index finger wants to find it then figure out optimum positions for the adjacent control modules.
Look at the pictures of Mockup #13. That shows where my fingers told me the shutter button needs to go after I shaped the handle for comfort and secure grip. Then I added the control dial and adjacent two buttons, guided at each step by my fingers.
2. The control dial should be positioned close enough to the shutter button that it can easily and reliably be located and operated by the index finger by feel, without any need to look at the controls.
After much experiment I have settled on a horizontal distance of 12mm between the center of the shutter button and the center of the control dial. This to some extent depends on the width of the shutter button but 12mm is in the optimum range. Any less is likely to be insufficient for functional separation. Any more is just forcing un-necessary side to side movement of the index finger.
Many cameras utilise excessive separation between the shutter button and control dial which serves no useful purpose but demands an uncomfortable amount of lateral movement which may for many users only be accomplished by shifting grip completely with the right hand.
3. The top surface of the shutter button and the control dial should both be at the same height relative to the natural movement of the index finger. This does not mean relative to the ground or any other fixed reference. It means that the index finger travels across an inclined plane as it moves from the shutter button to the control dial and that inclined plane is the height reference.
Sports car drivers will understand this. They want the accelerator, brake and clutch pedals at the same height so moving from one to the other is fast and reliable.
4. The control dial should be positioned and aligned on an axis so that flexion of the interphalangeal joints of the index finger bears directly on the dial. See the photos for further reference.
5. The upper surfaces of both the shutter button and control dial should be quite large and strongly textured (each very differently) so they are easy to locate and operate by feel.
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| Canon SX60. Canon has at last decided to give its SX line a front control dial just like an EOS DSLR. This one is on the same level as the shutter button, which is good, but the distance between the centers of each is 18mm. I find when using this camera that is too far. The control dial could easily come closer to the shutter button and angle a bit for better access by the index finger. |
Bring all this together and what do we get ?
Basically, mockup #13. The shutter button is located forward just where it wants to be. The control dial is close, but not too close, behind. In addition this configuration of shutter button and control dial on top of an inverted L style handle enables the provision of the highly efficient quad control set.
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| Photo courtesy of Imaging Resource Samsung NX1 showing near optimal positioning of shutter button, control dial and two adjacent buttons. If the function of those buttons can be user assigned this quad control set can provide very efficient operation. |
Does any existing (actual real working) camera utilise this optimal front dial position ?
Some get quite close. The Panasonic GH3/4 almost make it but there is un-necessary separation between the third and index fingers due to the shape of the upper handle. This makes the buttons behind the control dial very difficult to reach without shifting grip with the right hand.
Some Sony and Pentax DSLR style cameras with the control dial in front of the shutter button almost make it but again there is un-necessary separation requiring a stretch between the index and third fingers. In addition the two are at different heights and the control dial is on an axis away from that which would line up with the index finger.
I have trawled through many cameras present and past on the Digital Photography Review website and have managed to locate only two which come very close to the optimal configuration for shutter button /front dial design. As a bonus each has a quad control set.
Samsung’s first ‘all designed/produced in house’ entry into the ILC market was the NX10 of 2010. I bought and used one for two years. The designers of this camera got the relationship between the handle, shutter button and front dial just about right.
Samsung followed up with the NX20 which is similar to the NX10 but larger.
The NX30 and NX1 are the two cameras which I nominate as having the handle, shutter button, front control dial and adjacent buttons very close to the optimal as determined by my research.
Yes………...Samsung.
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| This is Mockup #13 again showing how easily the index finger can operate the shutter button, control dial and two adjacent buttons with user assignable function. This can happen without the need to move a muscle of any other finger. |
Now to the rear dial Although not optimal as a single dial, a well executed rear dial is very useful to have on a twin dial camera. A camera with twin control dials can allocate one to aperture and the other to shutter speed for quick adjustment in Manual Exposure mode. One dial can be allocated to direct control of Exposure Compensation in P, A or S Modes. Twin dials greatly speed up scrolling zoomed files in Playback.
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| Rear dials diagram referred to in the text below. The orange blob is intended to represent the thumb in neutral position. |
Existing cameras have rear dials all over the place. My research has led me to the view that there is one optimal location for a rear dial with the rest being suboptimal or worse.
Please refer to the diagram with my apologies for its poor quality. I find it easier to make things than draw them. But it illustrates 6 locations where rear dials can be found on various cameras.
Referring back to my little discourse on functional anatomy the diagram shows that the thumb can move side to side as shown by the arrows, without unduly disrupting the base of the thumb and its grip on the back of the camera. The end of the thumb (terminal phalanx) can also flex forward into the area occupied by #4 dial in the diagram. The movement more relevant to rear dial position is the side to side one.
Notice that the thumb cannot move up or down without releasing grip on the camera.
Analysing the benefits or otherwise of each rear dial position:
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| Photo courtesy of Digital Photography Review Olympus EM1 with rear dial in position 1. The right hand has to release grip and move up to operate this dial. |
1. Several cameras have a rear dial here. I have owned several of them. In order to prevent the thumb from bumping into it all the time it must be set forward. Thus located it cannot be operated unless the thumb rises up to get a purchase on it. But for that to happen the user must release grip on the camera with the right hand, support the camera with the left hand, move the right hand up, work the dial then put the right hand back down again.
I call this juggling. Support for and control of the mass of the camera has to be juggled from one hand to the next while shifting grip with one or both hands.
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| Photo courtesy of Digital Photography Review Nikon D5300 with rear dial in position 2. Notice the small thumb support pushed over to the right as required by this dial location. |
2. Again, several cameras have a dial here. I have owned a few. The problem is that you cannot have both a decent thumb support and a dial in this location. In order for the thumb to bear effectively onto the dial it must lift over the thumb support, which therefore must be very small and located way to the right side which, as I discussed in the previous post, provides a suboptimal thumb position.
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| Photo courtesy of Imaging Resource Samsung NX1 showing rear control dial in position 3. This is not bad but there is plenty of space on this camera to put the dial in the optimal position 6. |
3. Here is a somewhat favourite spot also. This position is not as ergonomically problematic as the previous two but is not optimal either. I have owned several cameras with a UIM here.
It is rather too high and wide to the left for comfort. The round module marked X on the diagram is located where the thumb wants to go. There is no space for a control dial here but I used the spot for a JOG lever in Mockup #13.
In practice operating a control dial in position #3 means moving the right hand position a bit. That’s not the end of the world but there is a better way…..read on.
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| Photo courtesy of Digital Photography Review Sony A7 with rear dial between positions 1 and 4. It is set forward so it won't be bumped all the time but the right hand still has to shift up to operate the dial. |
4. I have seen and used some cameras with a dial here. This location is ergonomically absurd. The dial cannot be used for functions in Capture Phase as the thumb is on it all the time.
Several cameras, mostly from Fuji, which do have a dial here benefit from an after market thumb rest which slots into the hotshoe, keeps the thumb off the dial and allows the thumb to take on the desirable angled position.
Fuji would do its customers a huge service by simply designing its cameras properly in the first place so owners don’t have to resort to aftermarket handles and thumb rests to achieve some level of ergonomic integrity.
5. Lots of cameras have a dial down here. It works just fine for Setup, Prepare and Review Phase tasks but is not desirable for Capture Phase as the thumb must be released completely from the camera in order to access the dial.
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| Panasonic FZ1000. This is a good rear dial. It is optimally positioned and has excellent haptics. The thumb can swing across to reach and operate the dial easily. The cutaway shape of the thumb support below the dial is a bit strange though. |
6. At last we have arrived at the optimal location. The control dial is embedded in a moderately prominent angled thumb support. The dial has sufficient projection and serration that it is easily operated by the thumb.
The thumb can easily swing right to operate the control dial or left to operate the JOG lever without disrupting grip with the base of the thumb.
Easy. Very small cameras probably lack the horizontal width to incorporate a dial here but the solution to that is to use a front dial, not a rear dial in a suboptimal position.
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| Here is Mockup#13 again showing the thumb in neutral position. It can easily swing right to operate the rear dial or left to bear on the JOG lever in the cutaway top right corner of the monitor area. Neither action disrupts the hold gained by the base of the thumb. |
How many cameras have this rear dial location ? Not many as it happens.
Sony’s A77 and A99 do although the control panel on both these cameras is very cluttered with buttons.
The enduring mystery at Sony is that some model lines have a completely different control system from others. All models are used by humans with the same hands and they all have to perform the same functions so why the difference in controls ??
The Panasonic GH3/4 and FZ1000 have well positioned rear dials which operate nicely. The A77 and FZ1000 have a strange cutaway thumb support beneath the control dial for reasons which elude me.
Nothing I could find at Canon or Nikon fits the bill.
Summary Existing cameras have front and rear dials scattered about as if the chosen location were the consequence of whimsy or habit.
Ergonomic analysis shows that there is in fact an optimum location for a front dial and an optimum location for a rear dial, just as there is an optimum design for the handle and thumb support.
Many recent market reports are describing a dramatic and accelerating fall in sales of all kinds of cameras over the last few years.
A major problem with many cameras is their ergonomics. Some are quite good, many are suboptimal and some are horrible.
Camera makers, designers and product development personnel need to get serious about ergonomic issues. They need to stop dithering around with model variations which make no sense ergonomically and start making cameras which are a pleasure to own and use.
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