One of the most common issues I see in photos on Flickr is a dullness -a hazy gray look to images. This is often very easy to fix. We'll use Auto Levels to fix the dullness seen in this photo:
Feel free to download this photo at it's full size here to follow along with the steps to fix it:
After downloading the photo, open it in Gimp. Do you immediately notice the dullness or hazy look to the photo? If not, that's ok. Over time it'll become more obvious to you.
Find and click on the "Colors" menu and then choose the "Levels" tool. This will open up a new window as seen here:
There's a lot of options in the Levels window, and we'll go over them all later. For now, just find the "Preview" checkbox towards the bottom and make sure that it's checked. This will change the look of the photo immediately when we make changes to it with the tool. If "Preview" is not checked you won't see your changes until you apply them by clicking on the "OK" button.
After making sure "Preview" is checked, click on the "Auto" button and watch how the photo changes. If you miss it you can click on the "Reset" button to undo the change so you can redo it.
See how the dullness is immediately fixed with Auto - Levels? The bells in particular go from dull looking to dark, as they should be. Click "OK" to apply the change to the photo permanently (what you see is just a preview, so hitting "Cancel" will cancel the change and the photo will go back to the way it was before you made the Levels change).
That's it for this photo -we're done!
When I first found out about this tool I did an Auto-Level on every photo I took because sometimes it made a huge difference even if I thought the photo looked good before using it. The more I used it the more I became aware of that dull cast in photos and could anticipate whether an Auto-Level was needed or not. I encourage you to try Auto-Levels on your photos to see what a diffence it can make. Sometimes it will make no difference, sometimes it'll make the colors in your photos go wacky and you won't want to use it. But, many times it can have a positive effect, so it's worth a shot!