I would not use the b/w setting on your camera as this will limit you with the final image. With most digital cameras they simply convert to greyscale and you get a very dull uninteresting looking image. Assuming you are using an image editor that has 'Channel Mixer' eg PSP or PS I use that to convert to b/w. This gives you control over the image, you can add differing amounts of Red, Green or Blue to give the final effect of having used a filter with b/w film. So to convert a colour image to b/w I add an adjustment layer and use colour channel mixer. Tick the box near the bottom of the panel for monochrome output. To preserve the same luminosity in the image make sure all values add up to 99. So for simple conversion use: Red 33, Green 33, Blue 33, do not use the constant control at the bottom as this will alter them all together. For the above conversion I used an orange filter effect by using Red 50, Green 25, Blue 25. I have not touched anything else on the image. For a Red filter effect use a higher Red value. Well there are lots of variations there to try but that is how I change to b/w it is quick and easy and gives you control. For a more advanced way I'll include a link in next message.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html