Solarization

Solarization is a term first used to describe over exposure. The visual effect of solarization is that it inverts the tonal range of the image to make a mono photograph that looks between a positive and a negative image. In the darkroom this is done by exposing a partially exposed image to white light before completing development. It can also be done digitally, heres how:

Technique 1:

First of all I made a copy of my background layer.

Then I went to Image>Adjustments>Black&White

Then I inverted the image.

Then I changed the blend mode to Difference.

This was my final result: 

Technique 2:

First of all I made a copy of my background layer

Then I went to Image>adjustments>black&white

Then I went to Filter>Stylize>Solarize

Then I inverted my image.

This was my final result.

Technique 3: 

First I made a copy of the background layer.

Then I went to Image>adjustments>Black&white

Then I used the Curves to make this upside down V

Then I inverted my image

This was my final result

Duotone

Duotone is the halftone reproduction of an image using one contrasting colour halftone over the top of another contrasting colour halftone. This is most commonly used to bring out mid-tones and highlights in an image. The most common colours are blues, yellows, browns and reds. 

Here are some examples: 

Here is how I made my duotone: 

First of all I went to Image>Adjustments>Black&White

Then i used the sliders to create my black and white image.

Then i went to Image>Mode>Greyscale

After choosing that I clicked flatten.

Then chose discard.

Then i went to image>mode>duotone

I chose duotone from the drop down menu

I then chose the colours i wanted to use 

This was my final image