Trick Photoshop

Step 1 : I have opened this free stock image in photoshop. You you want to use the same photo you can download it here. You only need to register. It belongs to Litil-divil-stock.

Step 2 : ress CTRL+SHIFT+U to desaturate the image.

Step 3 : Click the New Layer icon in the Layers palette and a new Layer 1 forms above the Background desaturated layer.

Step 4 : Click the Gradient Tool. Next click in the top panel at left to bring up the Gradient Editor. Before clicking on the Gradient Editor click the Linear Gradient that the red arrow points to.

Step 5 : Clicking on the Gradient Editor brings up the Presets at the top. You will not find as many Gradients in your version of Photoshop because I have installed other Gradients here. It does not matter and will not affect the tutorial.

Step 6 : I am clicking the 'Blue, Red and Yellow' Gradient to select it. You will find it in your version Photoshop.

Step 7 : Drag the Gradient Tool from the right bottom to the left top corner. You may of course drag in any direction. It will produce a different result. You can select any of the Gradients in the Presets also.

Step 8 : My image looks like this.

Step 9 : Reduce the Opacity to 25 % by dragging the slider. There is nothing hard and fast about it. It depends on the effect you are satisfied with.

And here is the effect. You can stop here or do the addititonal steps.

Step 10 : Press CTL+E. The Layer 1 merges into the Background Layer. There is now only a single layer in the Layers palette.

Step 11 : Press CTRL+L to bring up the Levels dialogue box. Note the Black graph in the middle and the Black, Gray and White sliders below it. The Black slider is to darken the image and the White to lighten it. The gray slider is to increase or decrease the highlights. Note that the ends of the graph do not reach  the Black slider at left or the White slider at right.

Step 12 : I have dragged the Black slider to the beginning of the black graph and the White slider to the end of graph.

Step 14 : Thi is how the image looks. Note I have not clicked OK as yet.

Step 15 : I have dragged the Gray slider to the right slightly to decrease the highlights. I have clicked OK.

And, here is the finished image. You can experiment in all the steps and you will get different results.

Other tutorials are here.