I will show you this simple step to make an perfect b&w on image lil' bit darker. 1st choose any image u think darky. You can see mine.
Yeah.. Friends of mine. They had a wonderful trip. Ha ha. Just look at their face.. excited already right? ha ha Okey, go to image > Mode > Lab Color. See image below
Then go to channel tab,delete the 'a' channel, just drag it to trash, 'b' channel should disappear as well.
And you've done. Easy step. Okey, you must go back to rgb or cmyk mode in order to save it in jpeg. first, go to image > mode > grayscale. and then once more, image > mode > rgb @ cmyk.
I hope you enjoyed this quick tutorial. BTW, afterall you also can change the b&w color without change the mode to lab color, just go to image > adjustment > black & white (Control + Alt + Shift + B) or desaturate the image (control + Shift + U) But the result can't be like this.