After seeing Shadow's thread on this i noticed a few people wanted to know how to achieve this in photoshop.
Well heres a quick guide to achieve the same effect, with a little more scope in terms of the contrasts you can achieve depending on the image.
1) Find the image you wish to use.
2) Render the image using your method of choice, for most photoshop users I would recomend the pen tool as it is incredibly flexible and gives the best results 9 times out of 10.
3) Desaturate the image. We wont be using a colour pallete for the image itself so using greyscale allows us better control on the contrast without warping the composition of the image.
And so here is our image all desaturated and ready for the next step... Curves!
4) Before we move on Fill the layer undernieth with white to be able to better see the effects of the curves and remember, we want to see some white bleed in and out of the render for a more seamless final image.
5) Ok on to making our image more defined... How do we do this? With Curves! Now I am aware some of you may have never used curves so I will explain to you there purpose and why I am using them.
Curves allow the user great freedom when determining the contrast of an image. The reason we use curves instead of the usual brightness/contrast filter is that unlike the brightness/contrast filter where you have 2 sliders, curves allow you complete control as to the amounts of black and white saturation as well as the depth of these values and this makes for a more flexible outcome allowing us to pick up on smaller details that would be missed using brightness and contrast.
So... Here we go
Select Image > Adjustments > Curves
You will now see a Dialogue box pop up within this you will see a diagonal line, this is where we define the Shape of the curves this will vary from image to image but i will show and example of the curves used in this tutorial.
In order to make a curve, simply drag the diagonal line to your desired destination. Experiment here untill you are happy with the results.
And so here is the result all white and black. I left a tiny bit of midtone grey behind to soften the effect, as I feel its a better representation and doesnt loose all of the facial detail either.
6) So, Now all thats left is to change the layer blending mode to darken/multiply. Doing this allows only the black or less than white values of the layer to be visable when layered on top of another layer.
7) Once this is done simply add a suitable background and sharpen/soften to taste.