At night, light conditions are completely different. Shooting photographs at night means dealing with lots of limitations due to the lack of light. Even if we are shooting a scene illuminated by moonlight or artificial light, or both, light intensity will be very low.
This means we need to use a high sensitivity or a low shutter speed (when we use a low shutter speed, we need to use a tripod for the photograph not to be moved).
If we use high sensitivity and we shoot photographs with film, our images will have grain. As we mentioned in the second course, grain is visually pleasant. As a matter of fact, many photographers use high sensitivity films to achieve this effect.
However, if we are using a digital camera and we use a high sensitivity, what we will get is "noise" in the photograph (there are cameras with high gamma which achieve great results; noiseless even when using a high sensitivity). Noise is not something we want in our photographs since it doesn't look good visually. In fact, the photograph looses quality whenever it has noise.
If we use a tripod, we will be able to use lower sensitivities; even seconds or minutes, since the photograph will be steady (no movement affecting the camera). As we learned in the previous course, each camera has its own minimum shutter speed; some have a minimum of 1 second (1/1); some 2 seconds, some 10 seconds, etc. But, always remember that DSRL or SRL cameras have the bulb function which will allow you to keep the shutter open the amount of time you need to properly expose a photograph.
Even though there are some compact cameras which have this function, the majority don't. They sometimes have a function for shooting photographs at night, which can prove useful at times. However, if we want to take a photograph at night, and there is very little light, it is highly probable that the photograph will come out dark using this function and we won't be able to expose this situation correctly.
This photograph was taken at 10.30PM. It had been raining so the pavement (street) reflects light.
Since I wasn't using the tripod, I used an ISO 6400 and an exposition of f/4 at 1/60. Since I was using a high sensitivity, I was able to use a shutter speed which would allow me to freeze the movement of the cars and not get a moved picture.
But, at the same time, since sensitivity was quite high (remember that from ISO 200 to ISO 6400, there are 5 points difference and each point means twice as much or half as much) the photograph lost quality and the undesirable "noise" appeared. When we see the photograph in a small size, it is not so visible. On the other hand, if we enlarge the picture, it will become more apparent.