Saturday, July 30, 2011
Night Time Photography
Night time photography has become a thing for me. It started when I saw a picture of Grosvenor Arch at night with stars in the background while on vacation in Utah some months ago. Since then I've been trying to create such shots myself and it's led to a lot of discoveries about what it takes to get that night shot. My first desire was a picture like the one I saw: the landscape lit by the moon with the stars in the background. That requires just the right timing both in time of day (well, time of night) and time of the lunar phase. As a result I went out a lot at night and had to try to figure out how to take different kinds of night shots. One of the first things I encountered was lightening; which has some of the same elements but I wont get into the differences here. One of those shots is the opening image, and here's another:
The biggest problem, I discovered, was finding an area that was bright enough that it didn't just silhouette with the stars in the background. So of course my first tries ended up being exactly that. Which is OK, because that can make some good pictures too. In this case it's a lot easier to get the settings right. Set the exposure for the sky, not necessarily the exposure the camera recommends, but with a digital it's pretty easy to just try a few settings, with just a little experience it's pretty quick, and snap. Unless there's a lot of moon, the foreground will be almost pitch black. Like I said, sometimes this is just what the doctor ordered.
One of the problems you'll first notice, if you're shooting anywhere near a city, is the color. Well sure light pollution will also degrade the quality of the stary scene, but that's just the way it is: no camera setting can fix that. What you'll find, though, is that the sky and anything lit by the city (clouds, reflection from the clouds onto the ground, whatever) will be red. This is because the artificial lights we use put out a very "cold" (from the point of view of physics and your camera settings) or red light. Your eyes adjust for it automatically so you can't always tell just looking at the scene, but your camera isn't quite so nimble. Sometimes red can be fantastic. I like using the color to add some mystery to my scene.
But you will at least want to know how to control it. The key here is your white balance setting. Just about any digital camera sold today (including the point-and-shot variety) have white balance settings. This is how you control what the camera thinks is white based on the lighting. Most likely if you don't know what I'm talking about yours is set to "auto white balance" which will try to guess what kind of light is being used. Direct sunlight, shade, and various kinds of artificial lights all produce different colors of light which has to be compensated for. Again your eyes do this automatically so you probably wont notice that something in shade appears a bit bluer than something in direct sunlight, but your camera does. Auto white balance works all right for normal colors outdoors but it becomes a problem at night.
If you're super sophisticated (I'm not) you'll have a white card to read the color temperature from and you can use "custom white balance" to really nail the scene as is. If you're like me and think buying and then carrying around and using a white card sounds terrible, you're pretty much stuck with guessing what the color temperature of your light is and picking from the presets. The two your camera is likely to have that will come in handy are "florescent" and "tungsten". I like the first because it does retain the mystical, red color without completely blowing out the red channel. Tungsten is probably going to be your most "photo-real" option. They both refer to what's producing the light (tungsten is the filament found in most light bulbs today) and they both emphasize the blue and downplay the red (though tungsten to a higher degree).
You have to choose what you want to be properly exposed. It's incredibly rare when shooting at night that all parts of your scene have the same light level. Now in a sense this is true for daytime photography as well, but the scale is much larger at night. The big thing here is that if you get the night sky at all you have the source of illumination (the stars) in frame. That's like trying to shoot with the sun in picture. You'll either blow out the stars or underexpose the foreground. The latter is what I described above: it's the easiest to set-up and still look good, but it does mean that your landscape will only serve as a horizon shape, not as any detail.
This can change if you manage to get moonlight into your shot. It's still tough to get the right amount of moon, especially since the only way to control that is pick the right point in the lunar phase, and it depends on your location how much light it's getting. In general I've found anywhere between 40% illuminated and 80% illuminated makes for good shots. One of the nice things is you can blow out the stars and they still tend to look good. So you have some freedom there, a wider range to work with.
Now when it comes to actually setting the exposure here's what I do. I figure out the absolutely biggest aperture I can use is while still getting my depth of field that I need, and then setting the shutter speed from there. The first is basically a guess, but an educated one and just depends on how deep my shot is and comes from experience (which I am still acquiring). The faster the shutter speed the less the stars move and the better image you get (unless you're going for the whole "sky rotating" thing which is an entirely different process normally requiring several hundred individual images). The stars aren't as blurred and same goes for anything in your shot that can move in the wind. All the same with my fastest glass (f/1.8) and shooting dark foregrounds I still rarely get faster than a 5 second exposure so nothing will actually be still. I find that after about 15" you can start to notice star movement (depending a great deal on level of magnification of course). 30" is about as long as I'd go if I cared at all that the stars stay still.
Use the light meter on your camera as a guide but know it's normally wrong, and often by two stops or so. Take a picture and check. It can be hard to tell in the dark with your bright LCD screen what the best exposure is but if you look to see what detail you can really make out, and the comparative brightness of different elements it tends to work all right. I normally take two or three pictures before I'm satisfied, at least for the first shot. Then I base my proceeding pictures on the settings of the first one. Always remember though that even if the lighting is exactly the same your subject isn't. How much of the sky is exposed, how reflective your subject is, etc... it can all change the appropriate exposure so pay attention!
A quick word about ISO: 100 is probably what your camera is naturally set at (though it may actually be a little higher and then darkens the image for 100, depending on the model). ISO refers to how sensitive the film/digital sensor is, the higher the number the more sensitive and thus the brighter your image is. The drawback to the increased sensitivity is noise gain. It's like turning up the radio and the songs louder but so is all the static. Generally you want it as low as possible while still getting the image you need. In daylight 100 is normally fine. At night it becomes a different beast all together.
The only way to tell what your comfortable with is trial and error. And that means taking the photos back home and looking at them in detail because the noise that will bother you probably wont show up on your LCD screen (though if it does, you're in real trouble!). It will depend on the size and type of your sensor, your camera's software for removing the noise and your opinion of what is and isn't acceptable. When looking at samples always take pictures with dark patches in them: that's where the noise shows up. For me, I've found ISO 800 is where I'm happy and I shot almost exclusively at that setting. Every once in a while I'll bump it up to 1600 but only rarely. I basically never go lower because that mean increasing the time I have to let the shutter stay open and that means adding blur to my photo.
The biggest advantage for me of night shots is that, if there are few clouds, you know the sky will be interesting. This is the problem with day shots: the foreground can be interesting but gray or even just blue negative space in the clouds can make the whole image seem drab. So taking a shot at night ensures that there's something there that adds to the picture. However, that attitude can get one (me) carried away and take shots that aren't interesting. A good rule of thumb is: would you take this picture if it were light out? The exception to that is when you can get a good silhouette and you're just blacking the foreground, but in general if it's not interesting in daytime it wont be a good night shot either.
The other issue to think about is where your light is coming from. Unlike the nice, bright sun, the moonlight isn't strong enough to scatter and give you diffuse lighting of everything. Ideally you want the moon to the back of your shot, and you want an open area for it to work on. It's why I favor shooting at lakes (plus they're so reflective, it's much easier to get the shot I want). You don't have to do this, if there's a shot your really want that's closed in you should get that shot. But then you need to pay attention to when the moon will be where you want it to, and what the best position will be to maximize that light.
Lighting the Scene Yourself:
This is tough, I've only tried it a couple times and with mixed results. You can do this using just your flash (still a multi-second exposure, but the flash goes once at the beginning) or with some other light source. A lot of people recommend car headlights but I have yet to be in a situation where what I wanted to photograph was in a position to be seen by my car's headlights. Flashlights can do the trick, and that's what I have tried. Here's the issues you need to be aware of:
Each light has its own color temperature and if you set the color for that light, some other part of the scene will be off-color:
That was taken with my flash, with the white balance set to 'flash'. You can see the sky added a lot of red.
The rule of squares is perhaps a larger problem. That is your light diminishes based on the square of the distance it shines. So something twice as close will be four times brighter if one light is used equally on each one. Making sure everything is lit the same amount becomes almost impossible to do. Your best bet is choosing a subject that's marginally far away from your camera in comparison to it's own depth (meaning a 1' deep subject should be several feet away) and then only having the one subject.
Sometimes though, you can only get the shot you want by lighting yourself.
All that said, night photography is fun and can produce some wonderful images. They make for good "wow!" shots if nothing else, and taking them is a great time. And now, here's the my personal favorite so far:
Here's where I keep all my night shots, you can see it go from crummy to... less crummy over time. :)