# Sensors and Lenses - Part 3

There’s a terrible tendency in cinematography to concentrate too much on the technology, overlooking creative skills that often make a huge contribution. In the last two pieces of this series we’ve gone into some detail on the historical background to current camera technology. In this last piece on the art and science of sensors and lenses, we’re going to consider what difference all this makes in the real world.

Figure 1 – the top diagram shows the relative sensor positions for a lens focusing on a scene with a viewing angle of 35 degrees. From our thin lens approximation formula (1/f = 1/u + 1/v), we can see that if “u” stays the same, that is the distance from the scene to the lens, and “v” increases from v1 to v2 because a larger sensor is being used, then by definition, the focal length (f) must also increase. This is the reason why a lens with a longer focal length is required when a larger sensor is used, and the viewing angle is kept constant (see figure 2 for more details).

Figure 2 – For a constant viewing angle of 59 degrees, the focal length can be seen to increase as the sensor size also increases from 2/3” sensor to the Arri Alexa 65. For example, to achieve a 59 degree viewing angle on a 2/3” sensor a focal length of 10mm is required, and to achieve the same viewing angle on a Blackmagic URSA sensor, a lens with a focal length of 26mm is required (all measurements are rounded to zero decimal places).

# Waves: Part 7 - Reflection And Refraction

Here we look at reflection and refraction, which figure highly in the cameras and lighting equipment used by broadcasters, to say nothing of the real word in which images are captured.

# The Back Of The Brain May Soon Rule The Roost

If industry reports are to be believed, Apple is poised to release a mixed-reality headset at some point in 2023. Of course, it’s anyone’s guess when Apple’s Reality Pro will actually see the holographic light of day, but one t…

# Learning From The Experts At The BEITC Sessions at 2023 NAB Show

Many NAB Shows visitors don’t realize that some of the most valuable technical information released at NAB Shows emanates from BEITC sessions. The job titles of all but one speaker in the conference are all related to engineering, technology, d…

# Interlace: Part 3 - Deinterlacing

Now that interlace is obsolete, we are left only with the problem of dealing with archive material that exists in the interlaced format. The overwhelming majority of video tapes, whether component or composite, analog or digital, would be interlaced.

# Compression: Part 6 - Inter Coding

The greatest amount of compression comes from the use of inter coding, which consists of finding redundancy between a series of pictures.