Digital Camera

Problem Description

Which button do I press now? I recently borrowed a digital camera to take some pictures (including some of those found elsewhere in this diary). The basic operations of taking and viewing pictures were easy to use. Anything more complex took some time to figure out, and was usually inconvenient.

HCI Analysis

Apple (1992) urges designers to use consistent controls in their interfaces. There are five major controls on the camera, and their usage isn't very consistent.

Buttons on the Agfa ePhoto camera.

Mode Switch
This ring-shaped control can be turned to three different settings: Off, Record (Take Pictures), and Play (View Pictures). The Record and Play settings are not clearly named, but this is understandable given the limited space on the camera.

Info Button
This tiny button (almost too small to be seen in the diagram) controls the display of information such as time & date, current picture number, and battery level. Its small size and position far away from the other controls ensure that the user cannot quickly press it (Card and Moran, 1986) to check on vital system information.

Shutter Button
This button is used to take pictures (when the Mode Switch is in the Record position). If it is pressed in halfway, the auto-focus locks in. The button must be pressed in fully to take a picture. Since this sort of interaction is fairly standard for cameras, I wasn't surprised by it. However, a larger-than-normal amount of pressure needs to be applied before the button presses in fully. If the flash is turned off, the only feedback given when a picture is taken is that the display freezes briefly. (Normally, the display shows a real-time view through the camera's lens.) It is easy for a novice user to mistakenly think they have taken a picture when they have only pressed the button halfway.

Zoom Buttons
These buttons control the camera's zoom feature when the Mode Switch is set to Record. When the Mode Switch is set to Play, they cycle through the pictures currently in memory. These uses are very intuitive, and have never caused me problems.

EasyPilot Button
This "button" offered the affordance of being turnable, but not pushable. This violates Norman's (1988) principle of visibility. The purpose of the button is to provide access to more advanced functions of the camera. To control it, a user must use a combination of turning to position a cursor on a menu, and pushing (clicking) to choose the selected item on the menu. Operation of this feature was very awkward, since the camera had to be held carefully in order to push the button. This made several simple tasks, like turning the flash on and off, much more difficult than they needed to be.

Deleting pictures is a problem with this camera. When I picked up the camera, I asked if a picture could be deleted. The person giving me the camera (a casual user) said, "I know you can do it. I'm not sure, though. Maybe you press this...no, maybe it has to be in Play mode." After a bit of struggling, she found the function in one of the EasyPilot menus. This menu turned out to be a bit confusing. Once delete mode is entered, a picture is shown, and the user is asked whether they want to delete it. When the answer, the next picture is shown with the same question. After every two or three pictures, the user is offered the option to exit from delete mode. The exit option not always being available violates Apple's (1992) principle of consitency.

Recommendation

Something as non-destructive as the info button should be much easier to press. There is no reason for it to be far away from the other controls. It should be located just below the zoom button. It should also be quite a bit larger.

The EasyPilot Button needs to be replaced with something that is easier to use. Even after using it for sever hours, I still had to be very careful when using the EasyPilot menus for fear of dropping the camera. It would also be helpful if the menu control were more self-explanatory for a novice user. A single button be used to replace this control. The new button would be used for clicking, and the Zoom Buttons could be used to move up and down the menus.

Some of the more often-used functions, such as the flash control, should be moved off of the menus and given buttons or switches of their own.

The menus should be standardized, so they present a consistent interface to the user. Particularly, the delete mode should offer an exit option at all times.

References

Apple Computer (1992) Macintosh Human Interface Guidlines. Addison Wesley. [Chapter 1]

Card, S. and Moran, T. (1986) User Technology: From pointing to pondering. in Proc. ACM conf. on History of Personal Workstations, Palo Alto. ACM.

Norman, D. (1988) The Psychology of Everyday Things. New York: Basic Books [Chapter 2]

rscherle@cs.indiana.edu
Last modified: Fri Mar 26 16:22:54 EST 1999