Kathy Loomis was kind enough to comment on my post on Vivien Maier asking this question, so I thought I’d give a full answer here. Most cameras now will allow you to shoot directly in Black and White so why bother to strip colour out in post-processing? There are three reasons I can see.
A glib but perfectly good answer is that if you shoot in colour you can keep that and have a Black and White version, but you cannot create colour from a Black and White capture. Why limit your options?
2. The underlying presence of colour allows a better Black and White image
When you use a programm like Lightroom or Photoshop to strip colour out you retain the tones in the original. Shooting in colour allows you to manipulate that colour first to strengthen the tonal contrast or to darken/lighten areas for effect. Let me show you with this image of a boat on top of a boat taken at the docks in Liverpool. This is the original image.
If I simply convert to Black and white by de-saturising it ( i.e. by simply sliding the saturation slider in Lightroom right to the left) this is what you get. Black and White yes but actually quite a lot of midtone greys,
So, let’s go back to the colour image and make some adjustments. I am exaggerating what I might do here just for illustration, but here I have upped the contrast and clarity, increased the blacks and whites. as a colour image it looks a little garish to me right now and if I was seeking to enhance the colour rather than convert, I would pull back on these adjustments.
However, when you then de-saturate the image you get this:
Bear in mind I’ve done this quickly to illustrate the point and I am not presenting it as the best image ever, (not least because I should crop that bollard out!) but I think you can see how you can enhance the strength of the image by playing with the colour first to get more contrast.
3. You can selectively retain colour for effect.
Using Lightroom there are three ways to convert to Black and White that I know of. there is the saturation slider I mentioned above. Or you can just click on the words Black & White in the basic panel. However, you can also reduce the saturation of each individual colour present in the image. It is therefore, possible to leave one colour in whilst stripping the others. That would not necessarily work for every image, but can be very effective where the colour appears only in one particular place. This is how I edited this image for example, with more care than the above example to leave her lipstick and the faintest bit of blusher showing.
(This picture is a sneak preview of a series of four posts coming up about my day learning portraiture last weekend!)
For these reasons I have been shooting in colour, but that is not to say that making a decision to shoot first in Black and White to train the eye for light and tones is not without merit. This article makes a great case for doing that and I might have to give that a go sometime. However, if you have a camera that shoots in raw format (as opposed to only JPEG) you can probably set the camera so that your display shows your image in Black and White but the raw file actually retains the colour. So, you will still need to do the post processing, but you can see and think in Black and white whilst working.
There are lots of blog posts around on this topic but this one from Northlight-Images is particularly strong on the technicalities if you want more information.
I hope that answers your question Kathy. If any other readers have anything they want me to write about please do contact me to let me know, I shall be happy to oblige.