[thelist] image resolution overview

Bob Meetin ontheroad at frii.com
Sun May 20 15:23:17 CDT 2007

I may have mixed this up (it happens) - you're right that a graphic is 
the way to go.  I think what partly confuses the issue (for me in 
providing explanations) is how this is accomplished in different image 
editing programs when including resolution in the discussion.


In photoshop, if I go to adjust image size, there are more options than 
non-techies should know about.  If I leave all checked (Scale size, 
contrain proportions and resample image), then change to 300 to 72dpi it 
also auto adjusts the weight and height giving a smaller dimension image 
in addition to lighter.

However, if uncheck resample and only adjust resolution to 72 not 
dimensions, it still produces an image the same size in MB as the 
previous paragraph.


If I ignore resolution and work with (and discuss) dimensions only, the 
explanation is simpler.  In photoshop or Gimp I take a 300dpi image and 
scale it down from 3008x2000 pixels to, say,  752x500 pixels, it is 
fairly easy to explain why the weight has somewhat proportionately 
dropped off as well.

3008px x 2000px at 300dpi = 2.54MB
 - converted -
752px x 500px at 300dpi - 133KB

When I add converting resolution to the discussion, it gets 
complicated.  In an article I read it said that web pages ignore 
resolution (I'm assuming that the div must be forcing the size).  I feel 
like I'm making it far to confusing, just having an 'old' moment.


Christian Heilmann wrote:
>> I'm having trouble putting into words ( non-techy words for a non-techy
>> audience) why it is important to adjust image resolution from whatever
>> dpi, 300-600, to 72 (or perhaps 96) for use on the internet and in
>> email.  Point me to a short article (a paragraph) would be fine. -Bob
> File size? Just show them the same image in 300 DPI and in 72 DPI and
> the file size it has and then show them a graph that shows how long
> this'll take on different connections to download, and even better how
> much traffic on the server it causes. Doug Bowman had a nice slide in
> his @media presentation two years ago that showed how much traffic
> moving blogger.com from non-semantic HTML to CSS saved, and he showed
> it to a non-tech audience by converting the traffic figures to CDs -
> now imagine 10000 CDs is easier than talking about Terabytes of
> traffic.

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