Geograph - photograph every grid square

There is a link at the foot of your profile 'Uses: Use of my photos around the site'. The first tab on the page is to 'Featured Images' http://www.geograph.org.uk/myphotos.php?tab=featured which will list any which have been used as 'Photograph of the Day' and show on which date they appeared on the home page.

One photograph is featured on the Home page each day. It is variously labelled as 'Featured Photograph', 'Photograph for today' etc. You can see past featured photos here https://www.geograph.org.uk/stuff/daily.php and, if you are a contributor, find any of your own which have been featured, and when, here https://www.geograph.org.uk/myphotos.php?tab=featured.

The 'This day in past years' index page is here http://www.geograph.org.uk/stuff/thisday.php
There is a link to it from the Explore page http://www.geograph.org.uk/explore/ which appears in the menu in the left side-bar.

[the beginnings of an answer]

Put simply, photographs are made of light. In good light, today's digital cameras make it difficult to take a technically poor photo. Sometimes, though, photos unavoidably come out dark or grey because the subject was in shadow, or it was getting late; worst of all, a cloud appeared overhead and followed you round while the distant landscape was bathed in sunshine. There are ways of making these photos reveal their subjects better.

This isn't a highly technical answer. It refers to features of commonly-used image editing or image enhancement software.

[to be continued]