This is a quick set of instruction on how to set the Black and White points of an image. If there is no true black and/or no true white the selection will apply to the darkest and the lightest points in the image.
Open the image and click and hold the eye dropper tool.
The tool will open a drop down - select the tool entitled "color sampler tool"
Using your eye place the tip of the sampler on the darkest point of your image and then repeat the process to select the lightest point.
Leaving these selection points go to the tool bar and select Image - Adjustments - Threshold.
Your image will now look like this:
Now move the threshold slider to the right the image will go to black with the exception of the lightest highlight. Do not drag the slider all the way - drag it so as to still have the last of the highlights visible. You will notice that you have missed the lightest point of the highlight area - as such the selection needs to be repositioned.
To reposition the selection point click on the point and holding the shift key and drag it to the lightest point as shown by the threshold tool. Your highlight selection will now be in the position as shown below.
Now move the threshold slider to the left to get the darkest shadows and once again you will see that you have missed the lightest point of the shadow area - the selection needs to be repositioned.
Now as you are not adjusting the threshold but using this as a tool to do your selection - do not click on OK, instead click on cancel.
You will return to your original image with the selection points still intact.
If you want to know why you need to do this - here are a few reasons: