When the light is dim at night, there are few things you can change to try to get correct exposure:
- Adjust to use higher ISO
- Increase ISO means increasing the sensor’s light sensitivity so the photo can be taken under dimmer light. However, remember that higher ISO will introduce more noise to the photo and too much noise (ISO 3200 & above) will reduce the contrast and sharpness too.
- Use larger aperture
- With larger aperture, more light will come in so the photo can be taken with faster shutter speed. However, this will be limited by your lens’ max aperture and lens with large aperture like 2.8 and below are usually more expensive.
- You also have to pay attention to the shadow depth of field effect of larger aperture. The effect may not be desired for landscape or night street shot for example.
- Use slow shutter and tripod
- With slower shutter speed, the curtain is open for longer period of time allowing more light to come in. Slow shutter speed is perfectly fine for static subjects but moving objects may create light traits or ghosting effect
- With slow shutter speed beyond hand holding limit like 1/20, 1/10 s or below, it is necessary to mount the camera on tripod or place the camera on solid steady surface to avoid shaking.
- Use flash
- Flash help to illuminate you subject but flash only has limited range to illuminate the subjects/foreground but not the far background
- Use flash to freeze the subject
- Direct flash tends to be too harsh on the subject and creating harsh dark shallow. For DSLR with external flash, bounce it off ceiling or wall if possible to create softer light.
Depends on how dim the light and what effects you want to create, you may have to use combinations of these options.
Lets look at some examples of night photography:
In the photo below, the environment is very dim with only street light, we have to tune up the ISO sensitivity and use a relatively large aperture of F3.5
ISO : 1600 Aperture : F3.5 Shutter speed : 1/25 s
For the photo below, it is using slow shutter speed with camera mounted on tripod to capture enough light.
ISO : 200 Aperture : F6.3 Shutter speed : 1.6 s
Note that the low ISO is used for two reason. First, lower ISO equal to better image quality with less noise and better contrast. Second, with low ISO, we can force the shutter speed to be slow to capture the light trail which is a nice effect for night photography.
Another point to consider is that in order to capture the blue tone of the sky and cloud instead of complete darkness, the best time to shoot is right after sunset when there is still light from the sky.
The above examples are shot using camera’s manual mode, which mean we set both aperture and shutter speed. With digital camera, it is easy to try and error to see which setting give us correct exposure for the main subject and are best capturing the atmosphere and mode.
Most camera nowadays do have more automated mode for night photography, for example the night mode. This mode is for low light situation and night time. The idea is similar as we discussed above, the camera try to use 1) higher ISO to increase the light sensitivity, and 2) use longer shutter speed to allow enough light in to capture the background. Typically the camera also fire off a flash to illuminate your subject and foreground. The flash will freeze the subject if it is moving. Bear in mind that the background maybe blur if hand holding the camera. For best result, use the tripod.