So Night Portraiture is one thing I really enjoy experimenting with. I learned how to properly do night portraiture quite late in my photographic learning but it's actually amazing just how simple it is. So you might have taken photos at night and then seen that hey, it doesn't seem to actually show you much, you just see your subject and nothing of the background. Then maybe you thought, hang on this flash is stupid, it's not going to light up the whole city. So I'll just shoot high ISO under some streetlight and that should do it. But then you probably got a horribly grainy image. So what do you do?
Well, it turns out that using flash at night isn't actually stupid at all, no you're not going to light up the whole city with it, but then again that's not really the point of it. What is useful to understand is that shutter speed controls your ambient light and so what you need to do is use your flash to illuminate and freeze your subjects and then drag your shutter to capture ambient light from the background. In automatic, you probably never got a good result with flash because your camera assumed the flash would light up everything and so it chose a short shutter speed that ensured none of the background would be visible. If you just dragged the shutter a little longer, you would've picked up a much nicer background.
Using a tripod is ideal, but depending on the level of light available, you may be able to get away with hand held shooting. It actually works best if your subject is in the dark and the background behind them is well lit up. This tends to give optimum results because you get a nice background and a much sharper image of your subject because your flash can do a better job of freezing them. Shooting during blue hour tends to give the nicest results for this.
To demonstrate how shutter can alter the look of your night photos, look at the following three shots taken successively with different shutter speeds:
35mm 1 /13s F1 .8 ISO 100 Flash Fired
35mm 1 /50s F1 .8 ISO 100 Flash Fired
35mm 1 /2s F1 .8 ISO 100 Flash Fired
So you can see just by dragging your shutter speed out a little longer, you can let in a lot more background light for your night photographs. Here are some more examples of night portraits:
Sometimes you may find when you're shooting past blue hour than the background tends to be very yellow because the street lights tend to be closer to tungsten rather than white. Here is what you might get:
This happens because your flash is white whereas the street lamps have a yellow tinge to them. This means your camera has to deal with the mix of white balances due to different light colours. What happens is what you see here, your subject is the right colour but the background is very yellow. Now you may like this look and I often enjoy this look, however sometimes you might like to try and shoot with a yellow gel on your flash instead. This way you can match the colours of the background lights and then correct your white balance in Lightroom, usually by using the eyedropper tool. This tends to give you a much bluer background.
Here are some examples of photos I shot using a yellow gel and then corrected in post
As you can see the background colours are no longer yellow and I feel give a very nice tinge of colour rather than a boring black. Or you can always go the other way and use a blue gel and make your background even more yellow/red such as the following:
So there you are, another great technique for you to try out in your own time. See what you can blend it with to make some great photographs. Enjoy.