Long exposure in Chicago
Why would one take a photograph in Chicago at night?
It was winter and it was late afternoon. The sun had already set and the light was that of night. Chicago is normally considered a smokey and noir city but that night those traits were somehow amplified. We were in North Clark St, a wide and congested avanue.
The cold and dry air made the colors vivid and the darkness loaded with cerulean nuances. As a contrast street lamps were saturated with warm tones. City lights seemed like colliding in a contrasting dance: warm colors and cold colors chasing one another.
Why do long exposure photography?
We were looking for a photo technique that could help us represent those visual stimuli and particularly that meaningful and exciting movement made of lights. Long exposure seemed to be our best shot to reach that target. But how does it work?
Difference between exposure and exposure time (shutter speed)
First let’s differentiate two often misread nouns: “exposure” and “exposure time” or “shutter speed”.
“Exposure” means the amount of light that enters the camera and that exposes the sensor. It depends on two variables.
The first is the aperture, namely the opening of a lens’s diaphragm that controls the light entering the camera (f/1 is the maximum aperture = much light – f/22 minimum aperture = little light). The second variable is the exposure time, namely the shutter speed that determines the duration of the aperture (standard exposure time is 1/60 or faster; 1/50 or longer is considered long exposure or long shutter speed).
Hence aperture and exposition time are the variables that control the light exposing our picture and they are inversely proportional. When I increase one, I have to decrease the other and vice versa.
Time Exposure: long exposure
Therefore, when we talk about long exposure we hardy refer to exposure meant as the total amount of light entering the camera (aperture + exposure time) but we refer just to the exposure time: the amount of time we set for the light to expose the sensor.
For a long exposure the time is to indeed be long, at least longer than 1/60 second. This is the reason why, in order to achieve good results, we will need a tripod to hold the camera still for the duration of the shot.
Long exposure: practice – first shot
Let’s say that, generally speaking, when we decide to take a picture it is to freeze a moment in time, but the aim we were targeting that night in Chicago was not that of freezing a moment. We wanted to free something unstable within an instant: the movement of those beautiful and engaging city lights and the chance for our subjects to mingle with them.
So, firstly we started by picking up a good location and putting the camera on a tripod. Secondly, we considered the darkness and the fact that, being night, we were to need more light than usual.
A way to get more light when shooting at night is to increase the ISO setting of your camera – carefully though, as an excessive increasement can be detrimental to image resolution – to make your sensor more sensitive to light. Hence, we change the ISO setting from 200 to 800. Thirdly, we set the aperture to 3.5 to get more light into the camera and we set the exposure time to 1/25 sec.
The shot you see below was a good result: the taxi seems indeed like moving without distorting the urban scape. Though we were not completely satisfied as we were looking for a realist perspective but a bit more dreamlike one.
Long exposure: practice – second shots
To our mind, the first shot was not completely able to connect to the atmosphere we would like to picture. In fact, we wanted the urban scape, though keeping its structure without distortion, to be characterized by a more enveloping movement, likely to drag the observer more vividly into the dance of the city lights.
Therefore we changed perspective: choosing a framing able to seize the transit of a subject “going away from” instead of “getting close to” the camera. Besides we chose a bigger subject matching more with the idea of “dragging the observer in to the picture” and we increased notably the exposure time up to 2 seconds. Consequently, we had to decrease the aperture to f/22 which made the lights vivider and sharper.
Here is the result in two different shots taken very closely and with the same setting: one with a subject coming in, the other with the subject going out almost dissolving.
Preference is personal but we think that both shots can comunicate the atmosphere we mentioned. In fact we got the image of a dreamy and enveloping environment that seems like dragging us within itself.
A urban scape that keeps its structure and vivid lights, expressing at the same time the mysterious imaginative universe we were chasing.