W3C home > Mailing lists > Public > www-style@w3.org > January 2010

Re: Making pt a non-physical unit

From: Brad Kemper <brad.kemper@gmail.com>
Date: Sat, 16 Jan 2010 10:37:06 -0800
Message-Id: <E2B8E754-F7F9-4717-8840-577B464B2A32@gmail.com>
To: David Singer <singer@apple.com>
Cc: www-style Group <www-style@w3.org>
On Jan 15, 2010, at 6:01 PM, David Singer <singer@apple.com> wrote:

> In both printed and electronic 'billboard' displays, a CSS inch may  
> be much larger, therefore, than a physical inch, so that a CSS pixel  
> subtends the expected angle at the eye for the typical viewer.

For electronic displays, this may happen to work out to the right  
angle through happy chance, or by the billboard manufactures making  
pixels that do not appear too large and blocky when you are some  
minimum distance away (and 'too blocky' might be based on expectations  
set by looking at desktop monitors at arms length). But I don't think  
you can say what a typical view is, because there is a great variety  
of viewing distances that are in good viewing range, and the pixel  
size will be based on some target minimum distance combined with cost  
and technology considerations. I don't think we should mention  
"subtends the expected angle", because it seems like an impossible  
fantasy to pick a typical distance, and unlikely to be considered by  
billboard makers. They probably develop their own guidelines for how  
far away their billboards need to be in order to be readable for a  
given pixel size. Anyway, I'm just critisizing rhe wording a bit (to  
avoid false expectations, especially as billboards also move to higher  
resolutions in the future), but I like what came before that sentence.
Received on Saturday, 16 January 2010 18:37:53 UTC

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