Autor: Redaktion

Digital Cameras Overview

The digital camera market has become increasingly diverse in recent years, serving a wide variety of users from high-end, high resolution dramas, to small flexible self-operated cameras for documentaries.

And of course the costs of these devices vary greatly from very mobile, very cost effective equipment on indie factual productions to high spec drama productions or advertising.
The choice of a particular camera is often dictated by the look you want to achieve and the budget of the production. However, it’s important to understand the basics of what’s inside a camera, so you can make an informed decision about the best equipment for your needs. 

The sensor size

In addition to the many different functions, codecs , and camera specific features, the sensor size is a core element of the camera classification. The sensor size is a measure of how much light can be captured within a pre-defined number of photosites on the sensor.

The density of these photosites will have an impact on the overall image capture ability of the device. That’s why mobile phone cameras, with small sensors shooting at 16+Megapixels, produce an image that doesn’t look better than a TV camera operating at a lower resolution. Smaller sensor cameras, capturing high resolution images, have a higher number of photosites on a smaller sensor surface, which can have an impact on the picture quality. 

The larger a sensor is, the shallower the depth of field. This can be compensated for with the use of high quality lenses. Larger sensors are often sensitive to light, although can deal with higher resolution capture better due to the number of photosites across the sensor surface.

HD DSLR cameras feature a 2/3 inch sensor and are mostly used in factual and online productions. The HD DSLR cameras have established themselves as flexible tools, and offer a very low entry price into the HD and UHD camera market.

On the other end of the scale is the highest quality digital cinema cameras, which are used on feature films and high-end productions. Here camera models with the largest sensors, highest resolutions and with the ability to offer RAW recording are the most popular, but also the most costly.

The Arri Alexa 65 boasts one of the largest sensors available, measuring 54.12x25.58mm (6560x3100 effective pixels), making its sensor three times larger than the sensor of a normal Arri Alexa .

Programmes wanting to achieve the "film look" should choose a camera that mirrors the  Super35mm sensor size of a movie image. This has become the benchmark for higher-end productions, although the Mysterium-X and Dragon sensors of RED are still noticeably bigger.

Sony used a sensor which corresponds to the Super35-size exactly in its F-Series cameras (F5 / 55, FS7 and others).

Most other cameras on the market that are used for TV production use smaller sensors compared to Super35 - with one exception: Full Frame HD SLRs like the Canon EOS MKII / III or the Nikon D3s. These cameras use a sensor the size of a 35mm photographic negative (36x24mm), as they are designed primarily as stills cameras, but can also record video.

The sensors used by the Canon C300 , Arri Alexa or all APS-C sensors still have a fairly similar size based on Super35. Panasonic and Blackmagic also offer cameras with sensor sizes ranging from Micro 4/3s down to 2/3 inch. This is similar to a smaller active area than a Super16mm movie image.

The majority of new cameras use single-chip cameras CMOS sensors, which replace the previous generation of 3-chip CCD sensors. Modern single-chip CMOS sensors operate faster, are more energy efficient and offer greater light sensitivity than their predecessors and CCD counterparts. Newer CMOS sensors have overcome problems such as vertical smear or blooming.

Because CMOS sensors, like all sensors, are effectively colourblind, the colour separation for an image recording uses a Bayer pattern. The algorithms (de-mosaicing or debayering) of the colour values for each pixel of this grid are interpolated, as part of the compression process within the camera. How much of the colour information that eventually ends up in the encoded image signal, depends on the type of codec and process used. RAW recording bypass processing, allowing colour to be managed by the post production operator or the digital imagining technician.

The internal recording format

All modern camera manufacturers offer different, sometimes proprietary, codecs for storing the image signal from the optical block. While some cameras have a very powerful sensor, the image signal can end up stored in a codec that has enormous losses. Therefore, it’s important to consider the combination of both the sensor size and an appropriate codec. Codecs with a sampling structure of 4:2:0 and a data rate of less than 50Mbit/s would limit the benefits of an excellent image sensor significantly.

The optics

The camera lenses in use today tend to fall into two categories; fixed focal lengths and zoom lenses.

Fixed-focus prime lenses are very high quality lenses with a fixed focal length. They have, in contrast to zoom lenses, a much lower error rate in the physical glass that is used to capture the image. This produces a higher quality image.

Zoom lenses are more complex in construction and therefore can have more errors. Chromatic aberrations and lateral chromatic aberration occur frequently. The light sensitivity and the overall image quality of zoom lenses is less than with fixed focal lengths, which can affect factual productions as the use of zoom lenses is mandatory for any observational documentary.

It is incredibly important to examine the quality of your lenses as they will have a big impact on your final programme.

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