Perhaps I have become used to the modern better-quality images, but
some old stored ones looked decidedly blotchy - especially the old
colour negatives I scanned years ago with a Minolta 35mm scanner. I
thought that Windows reconstructed all the jpeg images from some sort
of compressed format every time they are displayed, and there is some
loss every time. Originally I wanted to scan them all in the tiff
format but these files are too large. I have about 4000 images
laboriously scanned from old negatives and photos most of which I
can't get back anymore because I gave them back to the numerous
relatives. Now I'm worried.
If the monitor has a 6 bit LCD panel, there could be blotchy or banding
due to the color rendering process at the monitor. They take the 8 bit
value passed along the monitor cable, and then take two 6 bit values and
alternate values as frames are displayed on the screen. The human eye
interpolates the colors, to make something closer to an 8 bit color
Other monitors with have a proper 8 bit LCD panel (8 bits per pixel, on
each of the three primary colors R, G, B). And those monitors don't need
Naturally, your video card mode setting in the Display control panel, has
to be set to 24 or 32 bit color, so you're not limited at the graphics
card. If you were in 16 bit mode, you might see more banding, because
the video card cannot then represent all the colors properly.
LCD panels can also have problems delivering a good black level. Or alternately,
if the monitor is in "movie" mode, the monitor can dim the backlight when it
wants to make darker colors (for a mostly dark scene). Such dynamic contrast
usually annoys Photoshop users, who rely on the colors to remain consistent
for the entire session. Changing the monitor settings, via the monitor OSD,
is one way to attempt a correction (turn off movie mode).
Some monitors are carefully calibrated at the factory, while other brands
of LCD monitors are left with default settings that don't take the performance
of the panel into account. If you read reviews of some LCDs, the LCD only
gives a good result when they do the lab tests, after a manual calibration
procedure is followed.
The files themselves haven't changed, it's just the display path from the
file to your screen, where something is amiss.