I've gotten a lot of questions on Instagram recently when I began posting a series of night images to my gallery. What are your settings? What camera do you use? What lenses are you using? How is the foreground lit? How is the background lit? You forget after a certain period of time the wonder and discovery of how to take a certain kind of image. One where you can't even begin to know where the photographer started. I always get so excited when people ask because I am so passionate about the art, and I love the whole process. But I want to tell them everything all at once.
"It's really simple," I say. "Settings are ISO 1600 f/2.8 for a single thirty second exposure. The tent is lit from behind where my boyfriend is holding a flashlight. My friend and I managed to stay relatively still for the time period." Ok, they think about it. But how does the f-stop relate to the shutter speed, and how do both of those affect the what ISO sensitivity to use?! AND...how long was the flashlight backlighting the tarp?
So let me break it down a little further, because I remember learning all this stuff mostly through trial and error, reading, and looking at A LOT of other photos. I'll describe each part of the exposure in relation to how I took the above photo.
There are three parts to exposure- ISO, Shutter Speed, & Aperture
ISO Sensitivity- For me, it was easier to understand ISO in relation to film photography. Back in the film days there were 100 speed film, 200 speed film, 400 speed film, etc... The higher the number the more sensitive the film was to light. For instance, if I were to photograph the same subject in daylight with all the same settings except different ISO sensitivities, the one with the lower number would be darker than the photo taken on the higher ISO. It works the same way with digital, but we don't have to use a whole roll of film with one sensitivity! We can vary it from photo to photo. You always want to use the lowest number possible in any given situation in order to avoid unwanted noise. In the photo above I used ISO 1600, which is relatively high, especially for my Canon Rebel T2i. This was one of the things that allowed me to capture the stars in just 60 short seconds.
Shutter Speed- I think this is the part of exposure that is easiest for most people to understand. The shutter speed is how long the shutter of the camera is left open during the exposure. The longer it is left open, the more light is captured. With this photo I left the shutter open for one minute. When people shoot on automatic during the day, their camera usually sets the shutter speed at a trusty 1/60 second. This is fast enough to capture most scenes (not sports or action) but slow enough to expose the image at a lower ISO. Because I left my shutter open for a minute I was able to capture a dark scene. So you might ask, Kat, why didn't you leave it open for two minutes and get more stars in the pic? I didn't do that because the longer you leave the shutter open, the more noise (grainy appearance to the photo) you get. To answer the question of how long Craig was behind us shining the flashlight? It was very brief, maybe a second or two. With a wide open shutter and aperture (which I'll talk about below) and a high ISO setting, we didn't need much light to create the above effect.
Aperture- Aperture is one of the most important parts of the whole puzzle, or I guess I could say one of the more expensive parts. Aperture is the same as f-stop. It is essentially how wide the hole in your lens opens during the exposure. Aperture does several other fun things too, but I'll focus on its role in general exposure in this post. My aperture was set to f/2.8 in the above photo. This is KEY! Most cheap-o wide angle lenses only stop down to f/3.5. Good enough to take kind of crappy star pics. The fact that my lens goes down to f/2.8 made a large difference in the quality of my photos. It opened up just that little extra I needed to take in the light necessary without using too high an ISO or too long a shutter speed.
Any more questions feel free to ask in the comments below!
Also I want to note that I called this post "The TAKING of an Image" not "The Making of an Image." As much as I love and admire Ansel Adams and his work, I think he was wrong. I'm simply an observer who strives to capture the beauty of every day. I didn't make anything in the photo above. I just borrowed it for a little while. Ok, enough of my two cents! :)