Darkening images

I am often perplexed when I see flashes popping off at big stadium events- or inside a public building when the user is taking images of the architecture. Complete waste of battery power, and an annoyance to others around.
Take photos without flash where ever possible and brighten images in a computer image editor.

When you say repeated viewing I get a different slant on the problem.
I though you meant as taken.
O.K> These images are EXIF images which is a JPEG variant created for Digi Camera to include
such info as exposure data date camera make [sometimes].
A JPEG image is a highly compressed filed and every time it is opened and closed or copied to a folder or another device- the image will when closed[saved] will recompress thus losing part of the data.
Dong this repeated will eventually to total degradation.
So the thing to do here is to create a folder of the original images.
Better still when taking photos, if your camera allows it ensure that are taken as uncompress files such as TIFF or RAW- This makes for hughe files and therefoer reduces the number of images per card.
Then take 1 copy of all and save as JPEG
and use that exclusively for your viewing etc.
Copy the original sacrosanct files- burn them to a CD[Though do review the CD from time to time and make a fresh burn- because burned Cd's 'fade' in time also.[For other reasons but fade they do]