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Re: fear of "invisible metadata"

From: Sander Tekelenburg <st@isoc.nl>
Date: Fri, 22 Jun 2007 17:44:34 +0200
Message-Id: <p06240639c2a198b3826a@[192.168.0.102]>
To: public-html@w3.org

At 15:29 +0100 UTC, on 2007-06-22, Philip Taylor (Webmaster) wrote:

> Sander Tekelenburg wrote:
>
>  >> <li><a><img title="a butterfly" alt="an image of a butterfly"></a></li>
>  >>
>  >> That seems sort of pointlessly repetitive to me.
>  >
>  > Indeed. The text "an image of a butterfly" is complementary, not an
>  > alternative. It can make sense for a title attribute but is useless as ALT
>  > text.
>
> I am interested in this assertion.  Suppose, instead, the ALT text
> read "Papilio xuthus : photographed resting on leaf of Phelloderldron
>amurensis;
> image taken using Zuiko macro lens at 4cm on Olympus OM4-Ti, f/16, 0,5
>seconds,
> ISO 100 (ring flash); photograph taken 05:17 on Monday 18-Jun-2006, Kuril
>Island".
> Would that also be (in your opinion) "useless as ALT text", and if so, can
>you
> suggest what suitable ALT text might be ?

Again, it depends on what the image is meant to convey.

I think if the image is meant to convey certain visual aspects of a
particular butterfly, proper ALT text would describe those visual aspects
textually -- the camera settings are then completely irrelevant. But if you
mean to convey the effect of certain camera settings, then you're probably
mentioning those settings already anyway and are using the image to
demonstate their effect. So then proper ALT text would be a textual
description of the effect: "out of focus", or "rich colours", or something
like that.

It might be that the image conveys more than you realise initially though.
The only way to be sure is to place the ALT text text in its context,
replacing the image. Does it make perfect sense? Does it convey what you mean
to convey? Then it is proper ALT text. Otherwise it's not.

This might make you realise that the image contains more information that
needs described. It might for instance be clear from the image that the
photograph was made in bright sunlight, or during the night. If that's an
aspect that's relevant to what you're trying to communicate, and you haven't
described that -are only conveying it through the image- then that too should
be in the ALT text.

OTOH, it might also be that you're already describing all that, next to the
image. Describing the same again in ALT would be duplication, so alt="" is
then more appropriate.


-- 
Sander Tekelenburg
The Web Repair Initiative: <http://webrepair.org/>
Received on Friday, 22 June 2007 15:46:18 GMT

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