Re: Lossy, smaller JPG files

Subject: Re: Lossy, smaller JPG files
From: kcbillb2 <kcbillb2 -at- kc -dot- rr -dot- com>
To: Margaret Cekis <Margaret -dot- Cekis -at- comcast -dot- net>
Date: Thu, 15 Mar 2012 09:54:42 -0500

Margaret,

I'm not going to dispute what you say, since I haven't really kept up with the nitty gritty details of said software/devices.

BUT

I answered Dan the way I did from a purely technical point of view. .jpg IS lossy, no getting around that fact. You answered from the point of view of what is perceptible by the human eye on a monitor or other electronic display.

If, however, one is going to print (you know, on paper), any loss of pixels/data in an image will show up much more than it will on any electronic display.

Now, I just did a little research, and refer you to: http://en.wikipedia.org/wiki/JPEG , which will tell you way more than you ever needed to know about the .jpg/... format.

As far as I can tell, the standard hasn't been updated since 1998. As a result of that, my advice to Dan stands as written.




On 3/15/2012 8:34 AM, Margaret Cekis wrote:

Dan Goldstein asked whether saving JPG files (a lossy format) received from
someone else (without changes) in Paint Shop Pro, degrades the image
quality, even if he can't detect any loss of quality.
----------------------------
Dan:
I think that the answer is "not necessarily". Paint Shop Pro and other
modern high-quality graphics programs have much more sophisticated
compression and down-sizing algorithms than earlier programs (or even
earlier versions of the packages we are using now). They can compress JPGs
and other common graphics format files with less loss than earlier
compression methods.
Digital cameras and other sources of digital images have had such an
enormous jump in resolution that they exceed the capability of most common
display devices. If you try to display the multi-megapixel image captured by
a modern high-end digital camera on a laptop, or even on a high-resolution
wide-screen monitor, you'll be able to see only a small portion of the
image. These cameras now save images both in this super-megapixel "raw"
format, and in JPGs that "normal" PCs and monitors can handle. Unless you
have a billboard-size screen, downsizing JPG images to the resolution your
screen or application can handle will not degrade the image enough for your
eye to detect it.
Of course, if you still might want to display it on the digital billboard in
Times Square, you should save the original uncompressed file on an offline
drive or a DVD.
Margaret Cekis, Johns Creek GA



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References:
Lossy, smaller JPG files: From: Dan Goldstein
RE: Lossy, smaller JPG files: From: Margaret Cekis

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