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Re: [OM] Scanning Res for Web

Subject: Re: [OM] Scanning Res for Web
From: Garth Wood <garth@xxxxxxxxxxxxxxx>
Date: Sun, 28 Nov 1999 15:36:33 -0700
At 03:17 PM 11/28/99 -0500, Ron Spolarich wrote:
>Having returned the Olympus ES-10 and opted for the Nikon LS-30, I note an
>immediate improvement in scan quality.  Perhaps this is from better software
>or hardware or both.  In any event, I initially scanned my images at 1350
>DPI only to have Adobe Photoshop balk when I attempt to use the "Save for
>the Web" feature.  The "Save for Web" feature optimizes JPEGs for the web.
>I arbitrarily chose a DPI of 110 and had no further problems.  I suspect
>Photoshop couldn't digest an enormous file for web optimization.
>
>What I'd like to hear from the group is your initial scan DPI setting, size
>of image and optimization settings for JPEG web images.


Output or target DPI is meaningless, unless you're outputting to a printer.  
Just aim to have your entire image fit standard screen dimensions, such as 640 
x 480, 800 x 600, 1024 x 768, 1280 x 1024, etc.  (And no, it doesn't matter 
whether the image is exactly those dimensions, just aim to fit it within those 
dimensions.)

*Input* DPI, on the other hand, should be as high as possible (you can always 
do dimensional reduction of the image later).  This gives you more raw 
information to work with for any other operations such as image cropping, 
sharpening, unsharp masking, etc.  Then reduce to target screen size as a last 
step.  When reducing your image dimensions, always use bi-cubic resampling 
(it's the best quality overall).  Remember that, if people are going to be 
viewing your work in a Web browser, you have to subtract some pixels from each 
dimension (you'll have to figure out what you're comfortable with), since the 
browser's window is not the same aspect ratio as any of the standard screen 
dimensions.

As for optimization settings for JPEGs, sorry.  You'll find that each and every 
image you scan can tolerate a different level of compression before noticeable 
image degradation starts to set in.  You're simply going to have to experiment 
-- no single setting will work properly for all images.  Remember too that the 
output device you view the image on, as well as (in the case of RGB monitors) 
the video card your computer has, affects what you see.  Images viewed at 32 
bits per pixel (bpp), all other things being equal, look smoother and more 
"real" than the exact same image file viewed at 24bpp.  Same goes for 24bpp vs. 
16bpp, etc.

Garth


 
"A bad day doing photography is better
 than a good day doing just about 
 anything else."
 
The Unofficial Olympus Web Photo Gallery at:

   http://www.taiga.ca/~gallery/


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