Changing Scene Brightness in Long Exposure Night Photography

I think long exposure night photography is one of the most interesting types of photography out there. If you think about it, when you look at a photo that’s been captured over five seconds, fifteen seconds, thirty seconds or longer, you’re essentially looking at a span of time that’s been compressed into a split second. When was the last time you looked at an entire span of time in one blink of an eye? It’s kind of weird to think about it like this, but whatever the duration of the shot was, those seconds are what we’re able to see all at once. I know. This is just the stuff I think about on a daily basis.

Anyway, I’d like to talk about one tiny little area of long exposure night photography today and that tiny little area has to do with brightening up or darkening down your scene. I guess this “awareness” that I’d like to share with you is useful for long exposure photography that was taken in any type of lighting, not just night time lighting. We’ll focus on night time though because those types of photos are super cool and it’s easier to understand what I’d like to share when you think of photographing at night.

In this post, I’m going to talk about what’s referred to as the Exposure Triangle. If you’ve been around photography for a while, you’ve problem heard of this. If you haven’t, then let me tell you what it is. In photography, there are a few variables that determine how a photograph will be exposed. Each of these variables plays off one another to give you the shot you’re looking for. The variables are aperture, shutter speed and ISO. At the beginning, understanding how these three things work together can be a bit confusing, but after a while, they become extremely simple to understand and manage. And once you really get things down, photography becomes very exciting. I remember back when I first began learning about the Exposure Triangle, nothing seemed to click. Once I learned more though, and when things finally did click, I can tell you that they really clicked. What a great feeling that was.

Okay, let me get into this by giving you a quick example. Let’s say that you are all set up to take some night shots of pretty much anything. The subject matter doesn’t make a difference here. You’ve got your camera set up on a tripod and you know the shutter speed that you’d like to use. It’s going to be fifteen seconds. The reason you chose this duration is because you’ve either experimented with the same type of shot before or you simply know what you want from experience. Either way, fifteen seconds it is. Another thing you know is that you’d like your ISO to be set to 100. Again, this is from experience and you know that you can keep the noise in your photos way down by setting the ISO value low. So a 100 ISO value it is. As for the aperture, you start off with a value of f/4. Now, this value isn’t etched in stone like the other two are, so depending on how the shot comes out, you may want to change this one. The shutter speed needs to stay where it is because there’s movement in the shot and that duration will give you just the look your after and the ISO needs to stay where it is because you’ve learned over the years that that’s where it needs to be.

You take your first photo and review it on the back of your camera. Guess what. It’s too bright. Either the object you’re photographing is emitting too much light or there’s too much light in the atmosphere. Whatever it is, your shot is overexposed. What do you do? This is actually a real question that photographers ask themselves every day. To answer it, you need to decide which effect in your photograph is most important. We’ve already covered that the movement in the image is of the utmost importance, so the shutter speed can’t be touched. We also covered how the noise issue is important, so the ISO value can’t be touched. What’s left? Aperture. Since depth of field may not be an issue with the scene you’re shooting, you can increase the aperture value to something like f/5.6 This will let in less light, therefore darkening the scene.

Really, the trick is to decide on what’s most important to you in your shot. In the above example, movement and noise were the most important. Depth of field wasn’t important at all because you were very far away from your subject. After you changed the aperture setting, you didn’t even notice a difference with your shot beyond the fact that it became slightly darker.

Let’s say that you took another photo of the same subject, but on another night. This night was less illuminated than the last, so your image came out much darker than you expected. Let’s also say that you decided that noise wasn’t too big of an issue. You know you can raise the ISO value to 400 to give you the exposure you’re looking for without much grain at all, so that’s what you do and everything is fine.

Finally, you go back to your favorite photo area a third night and take the same photo with the same settings you used the previous night. After taking your first photograph, you realize that there must be a full moon or something, because things are very overexposed. Your image is washed out and you need to do something drastic. You lower the ISO value back to 100, but that doesn’t make enough of a difference. Then, you shrink your aperture to f/8, but you realize after some experimentation that F/8 is making things look a little funny. The scene is too clear and there’s not enough blur where you want there to be, so you put that back. You come to the conclusion that quickening the shutter speed is the only way to cut the light to capture the correct exposure, so that’s what you do. You set your shutter speed to ten seconds as opposed to 15 and your photograph comes out perfectly.

Photography is about experimentation and compromise. Cameras are only capable of so much and you’ll need to make decisions on the fly in regards to the quality of the photo as well as what you seek in the way of creativity. With experience and some creativity of your own, you’ll see that getting the perfect shot every time isn’t very difficult at all.

I hope I made some sense in this post today. I tried to give you a few real world examples of how you can use your knowledge of the Exposure Triangle to your advantage. If you have any questions regarding this post, please let me know in the comment section below. Also, you can ask questions and offer opinions in the Photography Technique forum at any time. Thanks for reading!