1. The grayscale
Image menu - patterns - gray, the channel is only one gray
Contrast
2. The brightness/contrast command
Image menu - adjustment - brightness contrast
3. The histogram - levels (Ctrl + L)
The X axis lightness change Y the number of pixels, said with a slope of the curve transition soft,
4. The levels command
Image menu - adjustment - levels (Ctrl + L),
Black slider move to 70, is to all 70 pixel brightness under 0 brightness, brightness is also under 79 pixels abandoned,
White slider to adjust to 180 means that more than 180 brightness all pixels into 255 brightness
In the middle of the 1.00 means black and white field pixel scale
5. Adjust the layer
Layer menu - new adjustment layer (adjustment) of convenient information
Below the adjustment layer on layer, will only work on a new layer below the clipping mask,