By Jiawei Zhao
Method
I apply the
set of usability principles (i.e., heuristics) proposed by Nielsen and Molich in 1990
[1] to the MacOS application Preview, that is used for viewing images, pdfs and
other documents. I organize the
evaluation by a set of identified tasks which cover the main features of the
application. For each task, I evaluated the user interface elements to check
their compliance with the selected set of heuristics to look for usability
problems or drawbacks. For each problem, I give one or more suggestions to
improve it.
All Defects Found
For Viewing
Pictures
1. Naming of the toolbar is inappropriate
In the “Markup Toolbar”, other than the tools used
to mark up, there is still a tool which is not used to add marks
on the picture, that is adjusting the size (see Figure 1). Hence, naming the toolbar
to “Markup toolbar” is not very reasonable. Doing so can mislead users and let
them think that the tool of adjusting size is not here. But it is indeed here,
which is not consistent with the user’s expectation. Therefore, this naming
violates the principle “Consistency”.
 |
| Figure 1 Inappropriate naming of the toolbar |
Suggestion:
Just name the the toolbar to
“toolbar” or “toolbox”, since these names are general and obvious.
2. Making a clickable thing be just a text
When a user is adjusting the size of a picture, there
is a text which shows the resulting size of the picture after adjusting.
Actually, one can click on this text to switch the format of the resulting size
(see Figure 2). Because it is just a text, a user can hardly realize that it
can be clicked. However, it is indeed clickable, which does not comfort to the
user’s expectation. Hence, making a clickable thing be just a text, which is
not reasonable and violates the common sense, does no obey the principle “Consistency”.
 |
|
Figure 2 Different formats of the resulting
size
|
Suggestion: A little
icon indicating the user can switch the format of the resulting size should be
put next to the text.
3. The button for cropping the picture is invisible at first
After the user selects one area on the picture,
there will appear a button named “crop” in toolbar. Then the user can click on
the “crop” button to clip the picture (see Figure 3). If the user does not
select an area, the “crop” button in the toolbar is invisible, which can
mislead users and let them think the function of clipping is not here. So, this violates the principle “Consistency”.  |
|
Figure 3 “Crop” button is invisible at the
beginning
|
Suggestion: Disable
the “crop” button when one does not select an area on the picture rather than
making it invisible.
For Viewing PDF
files
1. Search in the text
When
finishing searching, there is not a note or a reminder of which page the user
was in before searching. If the user is reading a very long e-book and wants to
continue reading after searching, he will have to find the page he was reading
before searching by himself. This violates the principle “Shortcuts” and this is a serious usability problem since it makes
the reading very inefficient.
Suggestion: Add a shortcut or a note
so that the user can directly jump to the page or get to know which page he was
in.
2. Highlighting and unhighlighting a text use the same operations
There are
no usability problems with highlighting. However, for unhighlighting, there is
a usability issue. More exactly, when the user wants to unhighlight a text, one
has to select the same color and brush the text he wants to unhighlight. So the
operations of highlighting and unhighlighting is same, which violates the
principle “Consistency”, since the
user can hardly know using the operations of highlighting to perform
unhighlighting.
Suggestion: Add an option of unhighlighting
is reasonable and desirable.
3. The
contents of the added bookmarks cannot be edited
Although a user can add bookmarks, the contents of
the bookmarks cannot be edited. Sometimes the contents of the bookmarks are
unmeaning and even unreadable (see Figure 4), if the user cannot edit it and
add meaningful contents, one can hardly know the meanings of the bookmarks. Not
allowing users to edit the contents of the bookmarks violate the principle “Speak user’s language” since users not
only cannot understand the original contents of the bookmarks but also cannot
edit the contents and add meaningful things.
 |
|
Figure 4 Unreadable and unmeaning contents of
bookmarks
|
Suggestion: Allow users to edit
contents of the bookmarks.
4. The
button for inserting a new page is unobvious
In order
to insert a new page, one can first click on the toolbar icon and then click
the “+” button on the far left bottom corner of the whole window (see Figure 5).
This inserting page (“+”) button is far away from other tools in the toolbar,
hence users will hardly notice it. And this violates the principle “Consistency”, since the same kind of
things should be located at the same location.
 |
|
Figure 5 Inserting a page
|
Suggestion: Put the inserting page
button (“+”) on the toolbar.
For
Preferences
1. Cannot undo the change of the window
background color
In the preference setting, one can change the
background color of the window (see Figure 6). However, the problem here is the
user cannot undo the changes. Maybe after trying several colors, the user
realizes that the original color is the best, but when he tries undoing by
press “Command + Z”, he founds it does not work. Hence, not providing “undo”
violates the principle “Clearly marked
exits”. |
|
Figure 6 Modifying background color
|
Suggestion: Allow the user to undo
the changes of the window background color.
Conclusions
After the
heuristic evaluation on the Mac’s built-in picture and PDF viewer Preview, I
found some usability problems. Most of them are associated with the principle
“Consistency” owing to the inconsistency with other applications or the user’s
expectation. Other usability issues are related to the principle “Shortcuts”,
“Speak the user’s language” and “Clearly marked exits”. The things I feel
uncomfortable about while I am using Preview are just the usability problems identified
through the evaluation.
Reference
[1] Nielsen, J., and Molich, R. (1990). Heuristic evaluation of user
interfaces, Proc. ACM CHI'90 Conf.
(Seattle, WA, 1-5 April), 249-256.
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