Open your picture in photoshop that is going to become pop art and duplicate the layer called "Background". (Just click the layer called "Background" and drag it to this icon at the bottom of the layer window to duplicate the layer.)

Rename this new layer "dots". (To rename a layer right-click on the name in the Layer Palette and select Layer Properties).

Create another new layer and fill it bright blue using the Paint Bucket tool .

Drag this layer between the two existing layers and rename it something meaningful i.e "blue". The image below shows what your Layer Palette should look like. This is the basic set up to begin.

Now working on the "dots" layer we need to clear out all the unwanted parts of the photograph. In this case I want to isolate Scarlett and delete the rest i.e lilac background and bit of text.

To cut out Scarlett I use the Pen Tool. Now to sum up how to use Photoshop's pen tool in a few sentences isn't easy...if you have never used the pen tool before, do the PEN TOOL TUTORIAL first.

Remember to make sure the pen tool is set to create a Work Path. See below.

*NOTE: You could use the eraser tool but the results won't be as professional.

Take the pen tool create a path around the person (or thing) and then make it into selection. Invert the selection (CTRL + Shft + i) and hit delete. Deselect (Ctrl + D)

Desaturate the "dots" layer (Ctrl + Shft + U).

Next adjust Threshold to something dramatic (still working on the "dots" layer).
Image >> Adjustments >> Threshold...
The settings I used are shown in the image below, but you will need to experiment to see what threshold settings works for YOUR image.

Using Threshold will leave the image looking very pixelated (jagged). So apply Gaussian Blur (approximately a 2-3 pixels should do it). Filter >> Blur >> Gaussian Blur...

In your Layers Palette right-click on the "dots" layer and select Duplicate Layer.... See image below.

Select New for the Destination Document. Now you will have 2 documents open in photoshop.

Working on your new document change the Mode to Greyscale.
Image >> Mode >> Greyscale
A dialogue box appears..."Discard color information?"...Click OK.

Now change the Mode to Bitmap.
Image >> Mode >> Bitmap
A dialogue box appears..."Flatten layers?"...Click OK.
Choose Halftone Screen on the Bitmap options window. Click OK. See image below.

Next appears the Halftone Screen box. Apply the settings shown below. Note you may want to experiment with the Frequency as this decides the size of the dots. Click OK.

Almost there with the dots. All that's left is to transfer the dots back to the first document. (See part C).

Change the Mode back to Greyscale
A dialogue box will appear...Make sure the size ratio is 1 and click OK.
Now change the Mode back to RGB.

In your Layers Palette right-click on the layer and select Duplicate Layer.
There should be 3 three options as the Destination Document. Choose your original psd (which should be the top one). See image below.

Your Layers Palette should look like the one shown below. You can close the second psd that you created..there's no need for it now.

The final step for creating the dots is to create a Clipping Path between the new layer and the "dots" layer.
To create a Clipping Path...hold down the ALT key and move your cursor between the 2 layers in your Layers Palette. When the cursor turns into a "double bubble" (see image below) click to create the clipping path.

Now link the "dots" and "Background copy" layer. See image below.
Merge Linked layers (Ctrl + E)

Your picture should now look like the one shown below..only better because it's not so small and compressed!

Now is a good time to Save (Ctrl + S) your work.

Open your picture in photoshop that is going to become pop art and duplicate the layer called "Background". (Just click the layer called "Background" and drag it to this icon at the bottom of the layer window to duplicate the layer.)

Rename this new layer "dots". (To rename a layer right-click on the name in the Layer Palette and select Layer Properties).

Create another new layer and fill it bright blue using the Paint Bucket tool .

Drag this layer between the two existing layers and rename it something meaningful i.e "blue". The image below shows what your Layer Palette should look like. This is the basic set up to begin.

Now working on the "dots" layer we need to clear out all the unwanted parts of the photograph. In this case I want to isolate Scarlett and delete the rest i.e lilac background and bit of text.

To cut out Scarlett I use the Pen Tool. Now to sum up how to use Photoshop's pen tool in a few sentences isn't easy...if you have never used the pen tool before, do the PEN TOOL TUTORIAL first.

Remember to make sure the pen tool is set to create a Work Path. See below.

*NOTE: You could use the eraser tool but the results won't be as professional.

Take the pen tool create a path around the person (or thing) and then make it into selection. Invert the selection (CTRL + Shft + i) and hit delete. Deselect (Ctrl + D)

Desaturate the "dots" layer (Ctrl + Shft + U).

Next adjust Threshold to something dramatic (still working on the "dots" layer).
Image >> Adjustments >> Threshold...
The settings I used are shown in the image below, but you will need to experiment to see what threshold settings works for YOUR image.

Using Threshold will leave the image looking very pixelated (jagged). So apply Gaussian Blur (approximately a 2-3 pixels should do it). Filter >> Blur >> Gaussian Blur...

In your Layers Palette right-click on the "dots" layer and select Duplicate Layer.... See image below.

Select New for the Destination Document. Now you will have 2 documents open in photoshop.

Working on your new document change the Mode to Greyscale.
Image >> Mode >> Greyscale
A dialogue box appears..."Discard color information?"...Click OK.

Now change the Mode to Bitmap.
Image >> Mode >> Bitmap
A dialogue box appears..."Flatten layers?"...Click OK.
Choose Halftone Screen on the Bitmap options window. Click OK. See image below.

Next appears the Halftone Screen box. Apply the settings shown below. Note you may want to experiment with the Frequency as this decides the size of the dots. Click OK.

Almost there with the dots. All that's left is to transfer the dots back to the first document. (See part C).

Change the Mode back to Greyscale
A dialogue box will appear...Make sure the size ratio is 1 and click OK.
Now change the Mode back to RGB.

In your Layers Palette right-click on the layer and select Duplicate Layer.
There should be 3 three options as the Destination Document. Choose your original psd (which should be the top one). See image below.

Your Layers Palette should look like the one shown below. You can close the second psd that you created..there's no need for it now.

The final step for creating the dots is to create a Clipping Path between the new layer and the "dots" layer.
To create a Clipping Path...hold down the ALT key and move your cursor between the 2 layers in your Layers Palette. When the cursor turns into a "double bubble" (see image below) click to create the clipping path.

Now link the "dots" and "Background copy" layer. See image below.
Merge Linked layers (Ctrl + E)

Your picture should now look like the one shown below..only better because it's not so small and compressed!

Now is a good time to Save (Ctrl + S) your work.