I have often come across people making statement that once you know what you are doing with Photoshop you shouldn’t use the levels tool but be using the Curves tool instead. Now I will admit that the curves tool is excellent and gives much more control over adjustments than the levels tool however this misses some very important points:

• Levels adjustments are often easier to understand than the equivalent adjustment in curves
• It’s often much quicker to make an adjustment using levels than it is to make the same change using Curves
• Curves are not as easy to control as levels
• You probably don’t understand curves as well as you think you do. If you doubt this then read Dan Margulis book "Professional Photoshop“.

The reason for my ramblings is the image above. This is the Matterhorn in Switzerland as viewed from the Klein Matterhorn. Whilst it’s not got the distinctive shape from this side that most people recognise as the Matterhorn, it is still an impressive sight.  I took the image at altitude on a bright day when there were high UV levels and it has suffered from a very strange colour cast. Whilst I had my Sony NEX5 set to AWB, the resulting image looks a little too blue but also had a green tint. As I shot the image in RAW format I reasoned I could correct the colour cast later as part of my conversion. I tried a number of adjustments in the RAW conversion including Auto White Balance, setting a custom white balance by sampling some of the clouds/snow and manually setting the colour temperature and tint. Unfortunately none were entirely successful.

After wasting quite a bit of time with the settings in RAW I decided to export the image anyway and correct the colour cast in Photoshop. I added a levels layer to the image and then opened the levels dialog. I checked each channel in turn to ensure the left and right sliders were touching the start of the histogram. In reality it was only the left and (shadow) slider that needed to be adjusted. Moving the slider in to the right so that it met the start of the histogram had a dramatic effect. Not only was the colour corrected, the contrast in the image was also boosted. Effectively what I was doing is setting the black and white point for the image on a channel by channel basis which is actually the first step in colour correction. Having used this method quite a few times in the past I knew it would work well under these conditions.

Now I could have made this change using the curves tool but it would not have been as quick and easy as the levels tool made it. So next time you have an image where you can’t seem to get the colour quite right give this simple tool a go.