Exposing for a dark or black background

[Matthew_Scullion]

Hi everyone,

I am sure this is a very simple question but I have searched around for an answer in the forums and cannot find one.

I am going to take some practice portraits of my wife this weekend around the house, just really trying out my new 50mm 1.4 lens and practicing my skills. What I would like to do is use natural light from a window to provide side lighting, poss using some sort of reflector for fill light. But I would like to expose to make the background black or at least very dark.

How do you do this? I am sure this is a one second answer for someone but I'd appreciate the tip being new to all of this!

Thanks in advance.

[Benji]

The obvious answer is to use a black background behind her. Even if her face or torso can't cover all of it, you can easily paint additional background in in Photoshop.

Benji

[teaking]

There are a few ways to do this...

... but why would you expose for the background in this case would it not be best to expose for the person and use a curves adjustment to darken only the black tones?

On to the answers lol, one way would be to shoot in manual and change to spot metering point at the black background and expose so that the meter reads -2 but isnt blinking. Another way would be to use EV compensation and dial in a negative amount and use the LCD to view the results and compensate till the back ground was black.

[CaptainNH]

It is much easier to achieve a low key image if you can use strobes. If you use a fair blast of power from a strobe to light your subject and then expose for the skin, you will quickly reduce your background to black. In fact with the right strobe, you can reduce even a light background to darkness.

Since you're using natural light (and English winter light for that matter ), I think you'll need to start with a black background. Nothing better for this than a black cotton bedsheet (leave the satin/silk sheets on the bed - far too shiny for this purpose ).

You'll need to try to stop the light from the window hitting this background - a big sheet of dark board would be good for this.

Similarly, if you use a reflector for fill, you'll need to direct/block this from reaching the background too.

If you can get a reasonable amount of light onto your subject, then spot meter on some skin, then you should be able to get your background dark, if not quite black.

It will help if you can get some distance between your subject and background to make sure it's thrown out of focus - this helps hide the wrinkles in the sheet and makes the slight variances in the darkness less obvious.

In post-processing, you can adjust the black point to turn your background black (or use a curves adjustment). Use a clone tool to make sure everything really is black and to get rid of any inevitable bits of fluff.

Also be aware of the amount of light that will be scattered at your background from furniture in the room - try to keep the light off that too!

Here's a lighting diagram (the horizonal softbox is your window!).

Good luck! Don't forget to post the results


EDIT: My youngest son wanted to know what the lighting diagram was. So we set it up exactly as the diagram and shot this a couple of minutes ago


Canon EOS 5D Mark II | 1/160 | f/1.8 | 85 mm | ISO1600 | -2/3 EV

Just crop and a slight boost to black point, then applied TRA's "Bitchin B&W" action.

In retrospect, if you can grab a bit of white card and reflect some light on the back of your subjects head, it would look much better with a rimlight.

[Matthew_Scullion]

CaptainNH, thanks for the superb and detailed information. I will try out as suggested and post the results.

Many thanks indeed.

[edbayani]

pose her beside the window and expose for her skin tone.

[PS*]

I am with edbayani, I always expose for skin-tone. but i am so new maybe i am just doing this wrong.

[kencaleno]

Originally Posted by PS*

I am with edbayani, I always expose for skin-tone. but i am so new maybe i am just doing this wrong.

Spot meter the face for skin tone-then open up 1-2 stops (Exposure compensation +2, if using A/Av mode)- checking in histogram, and adjust to suit.

regards, Ken