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Thread: Images with captions and alt
Number of posts in this thread: 6 (In chronological order)
From: Penny Roberts
Date: Wed, Aug 10 2005 12:00PM
Subject: Images with captions and alt
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Hello all,
I'm new to the list. I've had a look in the archives but can't
find exactly what I need to know.
If an image has a caption which describes the image and the
alt would be very much the same wording should I use an empty alt instead?
For example: an image has a caption (which comes straight after the image
in the code) reads "Figure 6: The catalogue search results screen" and the
alt tag is "Catalogue screen showing search results". Wouldn't that be
redundant to anyone reading the screen with images turned off and just
plain annoying and time wasting to anyone hearing the screen?
Penny
<*>
Penny Roberts
Radcliffe Science Library
Oxford
From: Jukka K. Korpela
Date: Wed, Aug 10 2005 6:00AM
Subject: Re: Images with captions and alt
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On Wed, 10 Aug 2005, Penny Roberts wrote:
> If an image has a caption which describes the image and the
> alt would be very much the same wording should I use an empty alt instead?
A caption should identify the image. An alt text should present the
information content of the image, or its relevant part. These are very
different jobs. In practice we might resort to label-like alt texts since
we are unable to write real alternative text, and _then_ the problem may
arise.
> For example: an image has a caption (which comes straight after the image
> in the code) reads "Figure 6: The catalogue search results screen" and the
> alt tag is "Catalogue screen showing search results". Wouldn't that be
> redundant to anyone reading the screen with images turned off and just
> plain annoying and time wasting to anyone hearing the screen?
It would be annoying indeed. But does it help the user to hear or see the
text even once? After all, neither the caption nor the alt text presents
the information content of the image; they just refer to it.
This is a tough question, and it depends on the nature and purpose of the
image. For example, sometimes a purely decorative image has a caption
(as text, not as embedded into the image). It is not quite sufficient to
use alt="", since the user will see or hear the caption and wonder what it
is about. In this special case, even alt="(decorative image)" would make
some sense. For an analysis of some types of cases, see
http://www.cs.tut.fi/~jkorpela/html/alt.html#content
An adequate textual replacement for some catalogue screen showing search
results would consist of text that explains, in sufficient detail as
required by the purpose of presenting the material, what the search
results consist of and how they are presented. This could consist of the
transcript of the same search using a text-only user interface.
It would generally be impractical to present such a large amount of text
in an alt attribute. Some other strategy would be needed. In this case,
I might use alt="(figure 6)" for the image and add text like
"There is alternative example of <a href="...">search dialogue
in text-only mode</a>, illustrating the same thing as Figure 6
but in a different user interface." Well, it can probably be made shorter.
The point is: write the alternate content into a document of its own
(perhaps a plain text file, obtained using a suitable tool for
getting an interaction log), and link to it with words.
--
Jukka "Yucca" Korpela, http://www.cs.tut.fi/~jkorpela/
From: Penny Roberts
Date: Thu, Aug 11 2005 12:00PM
Subject: Re: Images with captions and alt
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On Wed, 10 Aug 2005 14:35:55 +0300 (EEST) "Jukka K. Korpela"
< = EMAIL ADDRESS REMOVED = > wrote:
> On Wed, 10 Aug 2005, Penny Roberts wrote:
> > For example: an image has a caption (which comes straight after the image
> > in the code) reads "Figure 6: The catalogue search results screen" and the
> > alt tag is "Catalogue screen showing search results". Wouldn't that be
> > redundant to anyone reading the screen with images turned off and just
> > plain annoying and time wasting to anyone hearing the screen?
>
> It would be annoying indeed. But does it help the user to hear or see the
> text even once? After all, neither the caption nor the alt text presents
> the information content of the image; they just refer to it.
I think that I didn't make the situation very clear: the fact that it is a
catalogue screen showing search results *is* the information
being conveyed, the actual content of the screen (the search results) is
not important (so it could have "Foo Bar" for every title) .
To put it into context it is part of an interactive tutorial used
by university students to learn how to use the catalogue, by the time they
see the image they will already have run a search for themselves and
should have their own results in front of them. Because different people
learn in different ways we have found that whilst many are content with
text that says "you should now see a screen showing search results" some
need the visual reassurance of an image that confirms that they have
reached the right stage and some require the further assurance of the
caption to say "yes this is the search results screen".
> This is a tough question, and it depends on the nature and purpose of the
> image. For example, sometimes a purely decorative image has a caption
> (as text, not as embedded into the image). It is not quite sufficient to
> use alt="", since the user will see or hear the caption and wonder what it
> is about. In this special case, even alt="(decorative image)" would make
> some sense.
In this case the image is functional and necessary and the user would
hear the caption which describes it, so would a parallel to your example be
to make the alt="[screenshot]"
> An adequate textual replacement for some catalogue screen showing search
> results would consist of text that explains, in sufficient detail as
> required by the purpose of presenting the material, what the search
> results consist of and how they are presented. This could consist of the
> transcript of the same search using a text-only user interface.
The accompanying text already describes how to run the search and what they
will find on the screen (for instance that the closest match to their
search term is in bold text) and at this point they have (hopefully)
already run the search for themselves.
I suppose that a supplementary problem is that anyone using AT to
do the tutorial will also use it to run the search and therefore may not be
seeing the screen in the image anyway!
Penny
<*>
Penny Roberts
Radcliffe Science Library
Oxford
From: Glenda Watson Hyatt
Date: Thu, Aug 11 2005 6:00AM
Subject: Access and role
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I'm trying to wrap my head around 'access' and 'role' as a replacement for
accesskeys. How does this work? Can someone explain it in very simplified
terms, please?
Cheers,
Glenda
Ps I'm not looking to rehash the "accesskeys don't work" discussion. I want
to understand the new approach in simple terms, please.
Glenda Watson Hyatt, Principal
Soaring Eagle Communications
Accessible websites. Accessible content. Accessible solutions.
www.webaccessibility.biz
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From: Patrick Lauke
Date: Fri, Aug 12 2005 11:12AM
Subject: RE: Images with captions and alt
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> Penny Roberts
> If an image has a caption which describes the image and the
> alt would be very much the same wording should I use an empty
> alt instead?
Penny,
yes, I'd say that this approach is perfectly acceptable and in line
with the concept of providing "equivalent alternatives to auditory
and visual content."
Patrick
___________
Patrick H. Lauke
Webmaster / University of Salford
http://www.salford.ac.uk
___________
Web Standards Project (WaSP) Accessibility Task Force
http://webstandards.org/
___________
From: Mark Magennis
Date: Fri, Aug 12 2005 11:12AM
Subject: RE: Images with captions and alt
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Hi Penny. This is a very good question. Alt text is in essence a simple
idea but in practice it can be very difficult to get right.
The important thing is that the alt text for an image needs to give *the
information that has been missed* by people who didn't see the image. So
try reading the page but cover up the image and ask yourself "what
information did I just miss?". The answer may be one of:
* None at all.
Perhaps everything you need to know about the catalogue search results
has been already eplained in the text. So Alt="".
* That there is an image on the page.
This may be information in itself if, as Jukka has pointed out, coming
across the caption without knowing that there was an image will confuse
some readers. So Alt="Search results screen" to provide that
'information', and users will have to put up with the duplication.
* Some important information not fully explained in the text.
For example, if the surrounding text says "Figure 6 shows how the search
results are separated on the screen", then you might feel it needs
something like Alt="Search results screen showing alternating light and
dark background stripes used to visually separate individual search
results". If the unexplained information is more complex than this, then
maybe an Alt attribute is not sufficient and you need to link to a page
containing a longer explanation instead.
Don't be overly scared about having duplication if you really think that
the caption is going to confuse people who didn't know there was an
image. A little bit of duplication here and there is not a major
problem.
Mark
Dr. Mark Magennis
Director of the Centre for Inclusive Technology (CFIT)
National Council for the Blind of Ireland
Whitworth Road, Dublin 9, Republic of Ireland
= EMAIL ADDRESS REMOVED = tel: +353 (0)71 914 7464
>