unfortunately the colour (exposure and brightness) are different for all my sliders on all my pages. Who can I standardise this? Can I not just take a normal picture and a standard exposure makes the slider darker ?
You need to check the overlay color set for those images. I don’t see sliders in every page. Like in this page: http://www.citylife-nottingham.com/trips/ you have set the page header, with image overlay color to #f5f5f5 and the font color white (screenshot). Which is different from the home slider.
Let us know.