JPEGS not rendering correctly in Finder, Preview or Safari

Question

Need some quick help, guys.
Here's the symptom: JPEGs look lousy in the Finder, Preview, Safari, etc. Open them in Photoshop, and they look fine. Move the file to another computer, and it looks fine. It appears to me that any application that uses OS X to render to the JPEG is messing it up.
The files look like data is missing (e.g., 8 bit vs. 12 bit). Dark areas are banded.
Any clue what's not work, and how to fix, short of a new OS install, which I really want to avoid?

Answer 1

One of the causes of some images to appear poor, can be due
to an application used to view them, may be finding the smaller
thumbnail or reduced quality image, and showing you that one.
Sometimes, iPhoto or another image app will show a smaller
resolution image because there is also one of them available
in addition to the original larger resolution image. Or, in a few
other cases, an original may have been removed but a small
thumbnail or other file remains behind; a lesser vestige.
From other incidental exposure to this issue in other forums
over the past year or so, I have an idea that PhotoShop or
another pro app may have its own image archive to draw from.
Or it can see the correct larger image file, and avoid any small
resolution duplicate stored in iPhoto or another archive location.
Probably it would not be a good idea to re-install the OS X
since that would not necessarily fix the underlying cause
& it could return again; with little learned about how to fix it.
I've read about this kind of issue; but since I do not use
iPhoto (yet have a fairly good version of it, updated) this
problem is one I have never experienced in any Mac.
Perhaps a search of the Discussions archives or online
user forums via a google or other search engine, may
yield comparable issues and possible answers to them.
And, there is a fair chance that someone frequenting these
forum Discussions can point you to the exact cause of this.
I could find the most probable causes by doing a few searches
and likely get the correct matching results in about 15 minutes.
But it is time to consider sleep now.
For this issue, I would not reinstall the OS X; as that would
then require updating many apps, system steps, security
updates, java, quicktime, flash/shockwave, browsers, etc.
Unless you have a healthy clone you could clone back in
which pre-dated the emergence of this issue; a bootable
clone on an external enclosed hard disk drive. I have those.
Sometimes, iPhoto or other apps using images stored or
handled by such an image editing app, provide a lesser
quality resolution duplicate, and if I weren't so tired, I'd look
into where I think I read about this issue, within the past year.
Hopefully a frequent flier can recollect the correct path...
Good luck & happy computing!
PS: a quick search online of these words:
*Mac OS X jpg images poor quality* is
recommended; there are several results
of which some are likely candidates.
{edited}