WebAIM - Web Accessibility In Mind

E-mail List Archives

RE: Images with captions and alt

for

From: Mark Magennis
Date: Aug 12, 2005 11:12AM

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 REMOVED> tel: +353 (0)71 914 7464

> -----Original Message-----
> From: <EMAIL REMOVED>
> [mailto: <EMAIL REMOVED> ] On Behalf Of
> Penny Roberts
> Sent: 10 August 2005 11:38
> To: <EMAIL REMOVED>
> Subject: [WebAIM] Images with captions and alt
>
>
> 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
>
>
>
>
>
>
>
>