Who does not love a crisp, deep black background for a portrait? You can achieve this with the application of just two ideas, and just a little post-processing too.
We are talking about a couple of techy things in hopefully, a non-techy way. These two ideas will give you tips for how to make black backgrounds for your portraits.
No calculations necessary
As an erstwhile teacher of Mathematics, I should not apologize for numbers, should I? There is quite a lot of Mathematics in photography. However, you may be pleased to know that I think you can achieve everything, without thinking much beyond the basics. If you have a broad understanding of the concepts you will be absolutely fine.
These techniques are not just applicable to portraits.
Firstly, please think of stops of light as units. Using the term stop is like saying that something weighs 12 kilograms or that it is 10 miles away. As photographers, we tend to talk about stops and stopping down, but it is just as valid to say units. The thing is not to get bogged down in technicalities, the term stop is only a unit of measure.
The falling off of the light
The first concept might be stated simply as light falls off rapidly. Fleshing that out just a little, the amount of light available decreases greatly as you move away from the source of the light. But we are photographers and we do tend to think that a picture is worth a thousand words, so look at the diagram below:
In the example above, one unit of light arrives at our subject, one meter away from the window. If she moves two meters away, just one-quarter of a unit of light will now be arriving at her. Then, if she moves three meters away from the window, which is the source of light, there will be only one-ninth of a unit of light. The available light disappears very quickly.
It might suit some if I illustrate the same point with a graph (which, in the past, I have tended to introduce to students as a Mathematical picture).
How does that affect the background?
When trying to achieve a black background, you are interested in the amount of light hitting it. Again, pictures tell the story best. Both these photos had only white balance and very small adjustments to balance exposure done in post-processing.
The image on the left has the background close to the subject, about three feet (one meter) behind her. Then, on the right, the white background is about thirteen feet (four meters) back. You do not need me to do calculations, quote some nice formulae, to prove what is happening above. It is obvious, isn’t it?
In these photographs, the subject hasn’t moved and the exposure does not change. The background moves farther away, and the amount of light reaching it reduces rapidly. Even when the background is white, rather than the desired black, it gets much darker the greater the distance it is positioned from the light source.
In the practical world, there may be limits to what you can do, perhaps by the shooting space you have available. However, the message is simple, push the background as far away as possible, and even a seemingly small distance will help make it appear darker.
The background for this photograph was the inside of a room. The teenage Filipino boy was standing in a doorway, getting full benefit from the light source. The background, the far wall of the room, might be only eight feet (just over two meters) away, but it is getting very close to the blackest of blacks, isn’t it?
Combine this reasonably straightforward science, the way light falls away, with the science of the dynamic range of camera sensors and you will be a long way towards achieving black backgrounds for your portraits.
Please understand that the numbers I am using here are approximate. They do vary from camera to camera, and from the conclusion given by one source to another. But I am going for using what is easy, what is really needed to make the point so you understand.
Dynamic range is the measurement from the darkest to the lightest item which can be seen. Your camera has a great deal less dynamic range than the human eye. It is much less capable of seeing into dark and light areas at the same time. That is why, when your camera produces an image with blown out highlights, and blocked up shadows. But your eye can still see the detail of a bird, which sat in bright sunlight, and you can also see the black dog which sat in the darkest shadows. Your camera simply cannot see both at the same time.
Light the subject, not the background
It might be stating the obvious, but it needs to be said – the first step to getting a black background is to use a black backdrop. Then, if you can get the subject lit more brightly than the background, that will push the background into the underexposed, dark areas, outside the camera’s more limited dynamic range.
If you can throw some extra light onto the subject and have them exposed correctly, in the brighter end of the dynamic range, that will help to send the rest of the image into darkness. The brightly lit subject should be properly exposed. Then there is a good chance that the background will be outside of the part of the dynamic range for which you are exposing. It will, at the very least, be heading towards black.
Here is the setup for a portrait, with only natural light hitting the subject. It is not as obvious in this reduced jpeg as in the original RAW file, but the background is rather muddy, certainly getting towards black, but not the pure black you are looking for. In the original, you can clearly see folds in the cloth.
Here is the same set up again, with some extra light on the subject.
I think the point is illustrated. Is it clear that the background is worthy of the classic description “inky”? Other things could be improved with a few post-processing tweaks. They are presented to show the backgrounds, not as finished portraits, and I’ve only changed color balance and tried to balance the exposures.
Use the natural law (it is called the Inverse Square Law) which dictates that light falls away rapidly from the source, and the limited dynamic range of your camera and you are a long way to getting a good, deep black, background. Next, you can help complete it further in post-processing.
I am referring to Lightroom here, but there are equivalent tools in other software.
This is the photograph from the top of the article, as it first appeared out of the camera. You do not want to hear my excuses, but I did not get it as completely right in-camera as I would normally like to do. However, it turns out that is lucky, as it makes a good example for a post-processing in this case. Because the file was produced with the application of the ideas talked about above, it is very workable.
One of the best bits of advice I ever received, which I sometimes manage to apply, is to ignore the numbers. You should move those sliders till they give the look which you think suits the picture. Look at the photo and see what happens, take a breath, pause for a moment, and make some judgment as to whether it gives you what you’re looking for. Often this involves going a bit too far (whether it be with sharpening, or exposure, shadows, or whatever) and then dialing back a little.
I managed to do just that with this image. It makes me smile when I look at it now, a few weeks later, as I am slightly surprised at how far I went. I adjusted the color balance, brushed some negative clarity onto mom’s face, rotated the image counter-clockwise a little, but the exposure was not adjusted at all as the faces looked fine to me. Then I started pushing the sliders around.
Push the limits
It was a bit of a surprise to see just how far towards the negative I had moved the contrast slider. This may be counter-intuitive when you are trying to make parts of the image darker, but because we have got a reasonably well-produced file, we can get away with reducing the contrast, and this has the pleasing effect of lightening the hair and separating it from the background.
Of most significance to this exercise is the shadows slider which was moved in the opposite direction to usual. It was moved to the negative, to block up the shadows, rather than to the right, to try to pull out some detail.
I was also a bit surprised at how far I moved the black point. It seemed to work, though. As I say, I think it often works best if you move the sliders, without too much concern for the numbers they represent. Try to look at each photograph individually, rather than apply some sort of formula.
The final image had only a couple more, tiny, detailed tweaks.
A couple of other things.
How you decide to throw some light onto the subject of the photograph is for other articles. There are many other great Digital Photography School articles, which offer a huge number of suggestions for illuminating subjects. I thought you should know that I do very much like my LEDs, as I like being able to see the light. I also use reflectors. However, the first source of light in all the photographs above is natural light. You do not necessarily need a fancy kit.
In respect of the black cloth, most advice will suggest that you buy black velvet. I am sure it does an excellent job of absorbing light from all directions. But it is expensive, and with careful technique, it seems to me that another dark, non-shiny cloth can do the job too. One thing to pay a little attention to is making sure that you stretch the background cloth out a little. Try to get it as smooth and even as possible, with no creases, as any imperfections are liable to catch the light.
The power of photography! 25 years after the event, I paid a bit of homage to Annie Leibowitz’s photograph of Demi Moore. I was not trying to replicate it as such, just nod in the photograph’s direction. But I did manage to get a really black background, didn’t I? Please give it a go yourself.
Share your images and questions in the comments below. I’m happy to try to help further if I can.
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