The
sensor on a video or digital cinema camera is the image capturing device. Think of this
as being like the back of the eye of the camera. The light is focused through the lens
onto the sensor, which in turn converts this into electronic information. This is then recorded
digitally and can be manipulated in a post production environment. What was traditionally
an 8mm, 16mm, 35mm or even 65mm film plane is now replaced with the electronic equivalent,
the sensor. The job of the sensor is to turn reality into electronic images.
Sensors come in many different sizes and the size of the sensor has a direct relationship
to light sensitivity. Large sensors creates a more shallow depth of field to the image.
The critical factors affecting depth of field is the aperture setting on the lens, the sensor
size and the chosen focal length of the lens. Small sensors are easier to focus with than
a large sensor. Large sensors are more difficult to focus. Big sensors perform better in low
light, small sensors are less sensitive to light. Big sensors produce a shallow depth
of field effect, whereas small sensors produce the everything and focus look. For the cinematographer,
understanding the sensor within the camera is the key to producing cinematic results.
In the following examples, we can see that large sensors such as super 35mm, full frame
35mm or even 65mm produce a very shallow depth of field which sometimes can be desirable
and other times distracting. The half inch sensor, which is relatively small by today's
standards, has in the past been common for news gathering, event production and quick
turnaround work. It is easier to keep everything in focus with the smaller sensors. If we compare
the super 35mm sensor, which is the cinema standard, to the half inch sensor, we can
see there is a noticeable difference in depth of field. Compare this to the small sensor
in a Sony handy cam and the result is even more obvious. On the left of screen is the
image from a Sony handy cam. This is a very small sensor. As we can see, this really has
the all in focus look. If we compare this to the same image, filmed with larger sensor
cameras, we can clearly see there is more separation between the foreground image and
the background image due to the large sensor at work. The larger the sensor, the more shallow
depth of field between the main subject and the background. Therefore, on one hand we
have large sensors, super 35mm, full frame 35, 65mm and these produce a shallow depth
of field compared to the smaller sensors, which may be a quarter inch, a third inch,
a half inch. There is an obvious difference between the results. It is worth mentioning
that the small sensors tend to exhibit more noise than large sensors. Just like 16mm film
was more grainy than 35mm motion picture film, a large sensor contains more information than
a small sensor and this shows in the low light performance. There are other considerations
which will affect the looking quality, such as recording codec, resolution and of course
lens choice, the aperture you shoot at and as already mentioned, the focal length. Regardless,
sensor size certainly has a major influence on depth of field and low light performance.
It is therefore an important consideration when choosing the right camera for the job.
We have therefore demonstrated the effect that sensor size can have on depth of field.
For those filming with smaller sensors, it can be difficult or impossible to suitably
throw the background out of focus. This can make producing cinematic images very difficult
and contributes to what many call the all-in-focus look or the video look. There is a solution
to this problem. By using a data light in combination with an imager, one can project
an image onto a background and then throw the background image out of focus. The result
when recorded shows an out of focus background image with the foreground subject in focus.
We therefore have simulated the large sensor look with a smaller sensor. This means we
can produce cinematic images regardless of sensor size. As cinematographers, our job is
to create the look and feel of a scene through all the tools available to us. The tools provided
by data light, specifically focusing lights in combination with the data imager, enables
us to project an image onto a background, control the focus of the background image
and create truly cinematic results regardless of which camera you are using.
