There are a few reasons why people still resort to the in-camera black & white (b&w) mode, the two I hear the most is “ease of use” and the second “it allows you to be more creative in your shots” the second reason is because not all images make good b&w photos. However my own personal thought is there is very little reason for someone with a decent digital camera to be using in-camera b&w mode. The creative argument falls down when you can on most decent cameras shoot in photos in RAW, if you shoot in RAW and use the in-camera b&w the image you see on screen in b&w yet the RAW files will still contain all the colour information which would normally be lost if shoot as a jpeg. This allows you to be selectively creative when shooting as it gives you an idea how the shot will look in b&w.
I have often wondered why some people will take photos in this mode when you get far more creative scope doing this post processing (pp). When I suggest you convert to b&w in pp I don’t just mean using the “desaturate” or “greyscale” button in Photoshop or Gimp which is the same as turning on the b&w mode on your camera (from now on in this post I will refer to Gimp to perform a b&w conversion) . By far the best way to create a b&w image is to go into the “channel mixer” menu in GIMP check “preserve luminosity” and “monochrome” and now play around with the various sliders to get the look your after. The obvious advantage of using the channels in this way to create a b&w image is the flexibility it gives you, and allows you to create b&w photos that look more like photos taken with b&w film and a professional photographer adding grain actually works really well with b&w images it gives them more texture and a film like quality.
As you can see from the photos above there are many different version of black and white and the above images would only be possible if you have the colour information to start with (so don’t just throw it away). Another advantage of shooting in colour is the ability to convert to b&w and do some “selective colouring” what I mean by this is having a b&w photo yet have elements in colour (if you are interested in doing some selective colouring let me know and I will post a tutorial on the subject).