What role does the lens system play in a digital camera

As mentioned in section 2.4, the digital camera's ^lens system is often not given enough consideration. Many manufacturers draw the consumer's attention away from the lens, stressing instead resolution, price or other aspects. This is all the more surprising when you consider that digital cameras demand an even higher degree of optical performance than analogue compacts or even analogue ^SLR models. The following explains why this is so: Digital camera lenses have to focus the light onto a far smaller area than those in film cameras. Where CCDs have a diagonal measurement of, in some cases, 0.55cm, 35mm negative film measures 4.3cm. Also, as CCD resolutions increase while CCD sizes stay virtually the same, the actual area of the individual pixels decreases so they can fit into the same or similar area. On a CCD under 1" in size with three or four megapixels, for example, the width (or pitch) of the pixel is just six microns or less (1 millimetre is 1,000 microns). Whereas film-based camera technology only requires

In the diagram on the left, the lens from the analogue camera is unable to focus the Tight into a resolution fine enough to fit the individual sensors on the CCD. Lenses used in digital cameras, as shown in the diagram on the right, have to be of a higher quality to provide the lens resolution matching the incredibly small sensors on the CCD.

In the diagram on the left, the lens from the analogue camera is unable to focus the Tight into a resolution fine enough to fit the individual sensors on the CCD. Lenses used in digital cameras, as shown in the diagram on the right, have to be of a higher quality to provide the lens resolution matching the incredibly small sensors on the CCD.

The Four Thirds Standard

Co-developed by Olympus and Kodak and launched in 2002, this is a technological standard dedcat-ed to the needs of digital SLR camera systems. In its aim to maximise the performance of both image sensors and lenses, it established mechanical, optical and even communication standards. These cover, for example, the type and size of the lens mount, as well as the communication method for the lens and camera body. Just a year later, the Olympus "E-System", the first digital SLR camera system based on the Four Thirds Standard, was released.

optical systems that focus light to a resolution of 10 microns, the CCD in our example requires a lens that can focus light to a resolution of three or four microns.

Also, due to the construction of the individual sensors, which are surrounded by a "wall" on four sides, the CCD cannot accept light coming at an angle. Therefore, to focus the light so it hits the sensor surface at a more or less perpendicular angle, the lens should have a nearly telecentric construction. This is possible in most compact models because of their small CCD size (which is only a fraction of the area of a 35mm film). However, it is too impractical to make nearly telecentric lenses for digital SLRs with CCDs based on the larger 35mm film format. The lenses would be so large and expensive that many manufacturers decided to trade in quality for convenience.

However, the Four Thirds Standard put an end to this unsatisfactory compromise. Jointly developed by Olympus and Kodak, it established, among other things, the optimum sensor size for DSLRs to allow the production of near telecentric lens systems. The standard also describes the method of communication between the lens and body, which allows some unavoidable optical aberrations to be corrected electronically. The Four Thirds Standard is open to any manufacturers wishing to follow its guidelines, allowing photographers to use camera bodies and lenses from different manufacturers.

Lens designed for Film

35mm film cameras.

I

Near telecentric lens as in CCD

ZUIKO DIGITAL lenses.

Near telecentric lens as in CCD

ZUIKO DIGITAL lenses.

Film is tolerant with respect to light hitting it at an angle. Even at high resolutions, film can collect light falling at a high angle of incidence without a critical loss of brightness.

The following effects occur when light hits the sensor at high angles.

1. Reflection onto neighbouring pixels.

2. Crosstalk between neighbouring pixels.

3. Loss of brightness since some of the light cannot be captured by the sensor.

These effects reduce the charge on the pixel, resulting in poorer signal to noise ratio, corner shading and poor colour reproduction.

The near telecentric construction of lenses optimised for the Four Thirds Standard ensures light hits the sensor at almost perpendicular angles. This guarantees edge-to-edge colour, clarity anahigher brightness.

The Olympus E-System

This comprises digital SLR bodies, interchangeable lenses and a host of other accessories for professional and very ambitious amateur photographers. It is the world's first system based on the ^Four Thirds Standard. Photographers benefit from the dedicated optics which, thanks to the use of the standard, are able to combine a large aperture with a compact form and light weight. The standard even allows the same angle of view to be achieved at half the focal length.

There is another reason why you should always look for good optical performance. In addition to picture sharpness, the lens system significantly influences colour reproduction and the ability to shoot in poor light conditions.

Finally, it would be misleading to think that all photographic errors could be corrected with the help of newer and improved ^image editing software. The opportunities offered by various software programs are certainly fascinating, yet even they cannot perform miracles. What has not been recorded in the first place cannot be improved or added to. An excellent picture can rarely be made from an image which has been over or underexposed, for example, or poorly digitised. Therefore, people who insist on first-class picture quality and do not want to waste time on image editing should make sure that their camera includes a high quality optical system.

Digital Camera and Digital Photography

Digital Camera and Digital Photography

Compared to film cameras, digital cameras are easy to use, fun and extremely versatile. Every day there’s more features being designed. Whether you have the cheapest model or a high end model, digital cameras can do an endless number of things. Let’s look at how to get the most out of your digital camera.

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