Digital camera equipment

Digital camera equipment is less easily classified by image format than film simply because of the huge variation in sensor size. Cameras can, however, be put into broad categories based upon the market for which they are aimed and like film cameras, this dictates the level of sophistication and cost of the equipment.

The equipment falls into a number of main types (see Figure 2.16):

1 Specially designed compact type cameras for point-and-shoot snapshots. Mobile phone cameras - with fewer features - can also be included in this category.

2 Hybrid cameras. There are a range of different designs, but they often bridge the gap between compacts and SLRs, containing many of the features of both.

3 Small-format SLR cameras. Up to 35 mm, these fall into two classes: Prosumer (or semi-professional) which are cheaper and aimed at the serious amateur, and professional SLRs based on existing film cameras, retaining their same 'front-end' features, but permanently housing a digital sensor in place of film.

4 Medium- and large-format digital backs. These are high resolution, capturing either an entire frame at once or in the larger formats scanning down the frame using a linear sensor. The majority are digital backs, which you simply attach and detach from your present medium- or large-format camera in the same way as a conventional rollfilm magazine or sheet film holder. There are a few available, however, that are built on to camera bodies.

Figure 2.16 Types of digital camera: (a) high-end compact, (b) hybrid and (c) professional SLR.

Point and shoot: Mobile phone cameras and compacts

At the lowest end of the market are mobile phone cameras. Pixel counts of up to 5 megapixels on sensors in mobile phones are now beginning to rival and surpass those in the compact point-and-shoot cameras of a few years ago. CMOS image sensors were first used in mobile phones; at the time the noise levels and low resolution associated with CMOS were unacceptable for other cameras, but the advances in the sensors in terms of both smaller pixel sizes and improved noise suppression have meant that image quality has steadily improved. These improvements have lead to the development of full-frame 35 mm CMOS sensors now used in professional SLRs. The optics on mobile phone cameras tend to be low quality, often plastic, however this is of much less importance bearing in mind the way in which these cameras are used. Interestingly, mobile phone cameras are currently the fastest growing part of the digital camera market. In recent years it has become common to see mobile phone images sent in by the public used in newspapers and television reports, where it would not have been possible to obtain such images unless a journalist had been on the scene.

There are a huge variety of compact cameras available, with many of the features typical on film compact cameras, such as built-in flash, a large variety of exposure and shooting modes, including movie modes and red-eye reduction. There has been a trend towards miniaturization by some manufacturers, aided by the ease of producing small CMOS sensors and the fact that many have scrapped viewfinders in favour of viewing the image on the LCD screen at the back. The other types of compact commonly available look more like an SLR, but tend to have smaller sensors. Nevertheless, recent models have sensors of up to 10 megapixels. Both types tend to be more automated, often without manual options. They may also only have digital zoom rather than optical zoom and output still image file formats may be limited to JPEG only. Prices are widely variable and continually coming down. The shelf-life of a particular camera model continues to decrease; often the next version in a successful range will be out six months after the last.

At the top end of the compact market are a couple of cameras aimed more at the professional (see Figure 2.16(a)) - the point-and-shoot for the professional photographer, if you will. They are significantly more expensive than the majority of compacts, up to three times more than those at the cheaper end but have fewer automated features, some without zoom lenses. They allow manual setting of most features; capture to RAW file format and sensor resolutions rival those of some SLRs. The cost is in the quality of sensor and the optics.

Semi-professional SLRs (Prosumer cameras)

These cameras are hybrids, with many of the automatic features of compact cameras, but with more of the manual controls available with SLRs. Where professional SLRs may be sold as camera body only, these tend to be marketed as all-in packages. Currently they do not include full-size sensors, i.e. of equivalent size to the film format. Actual sensor sizes are variable (see Figure 2.14). The upper limit of effective resolution of the sensors in these cameras is around 10.1 megapixels, which can theoretically produce an output print size of nearly 330 mm X 220 mm and a file size of around 30 MB. They may have a range of interchangeable lenses and a variety of accessories available and are sometimes compatible with the lenses from the equivalent film cameras. However, the smaller sensors mean that there will be a conversion factor between the lenses. The lenses are also of lower quality than the professional ranges. This is not to knock them however; some of the hybrid cameras produced by manufacturers such as Canon and

Nikon in recent years contain sensors that surpass the performance of those in professional ranges of a few years ago.

They are aimed at the serious amateur and their price reflects their hybrid status, being significantly more affordable, sometimes half the price (including lenses) of the professional equivalent (body only).

Full-frame SLRs

These cameras are the closest to conventional film formats and are aimed at the professional. The camera bodies are almost identical in design, apart from the image sensor and related optics, processing and the LCD screen on the back. Some manufacturers have even maintained the position of the main controls to make the transition from film to digital even easier. Sensors are full-frame; the same image size as 35 mm format and this means that there is no lens conversion factor required. The variation in price is therefore down to number of pixels and hence resolution, with an upper limit at the time of writing of around 16 megapixels, giving an output file size of nearly 50 Mb. Often sold as a camera body only (although some may come with cheaper lenses), they are designed to replace the film camera body in a professional kit, without requiring additional lenses or accessories. They tend not to have the array of automatic features of their semi-professional counterparts, with fewer modes and more manual control. These cameras have been widely adopted by photojournalists, in particular sports photographers, who often carry laptops as part of their kit and are able to download, crop and adjust their images before sending them wirelessly to their picture editors within a matter of minutes. In these types of photography, speed is of the essence and can mean the difference between your images, or someone else's, being used and syndicated.

There are also a number of medium-format full-frame digital SLRs available. Significantly more expensive, the sensors are larger than those used in 35 mm, but smaller than the physical dimensions of their film equivalent (36 mm X 48 mm is quite typical). More commonly available are digital backs for this format (see below).

Digital backs

For highest quality digital images intended for big prints, larger file sizes are required. This is made possible by fitting a digital back to a rollfilm SLR or view camera (see Figure 2.17). At this level, CCDs dominate. There are two main types: either frame arrays, which capture the entire frame at once, and are mainly medium format (although some can be attached to large-format camera bodies), or digital scanning backs, which use a trilinear CCD array (three rows of sensors, each capturing red, green or blue), and are designed for both medium and large-format cameras. The single shot arrays are not equivalent in size to their film counterparts, the largest currently available at around 49 X 37 mm, but with pixel counts of up to 7216 X 5412 (39 million), a sensor of this size produces image files of over 100 MB and resolution easily matches that of mediumformat film.

Figure 2.17 Digital backs: (a) A digital back for a medium-format camera (image courtesy of Phase One, Inc.), (b) a scanning back containing a trilinear CCD array for a large-format view camera (image courtesy of Better Light, Inc.).

Figure 2.17 Digital backs: (a) A digital back for a medium-format camera (image courtesy of Phase One, Inc.), (b) a scanning back containing a trilinear CCD array for a large-format view camera (image courtesy of Better Light, Inc.).

Because digital scanning backs physically track across the camera image plane throughout an exposure, subject matter is limited to still-life as both camera and subject must remain still for a couple of minutes. Therefore they cannot be used with flash, and using tungsten illumination you must avoid any lighting intensity variations (such as minor flickering) because this will show up as a band across the picture. A full colour image of many millions of pixels is built up line by line to give image files at the top end of the scale of over 400 MB.

Clearly, dealing with files of this size is a completely different matter compared to the convenience of using digital SLR. There are huge storage requirements involved and processing must be done predominantly on a peripheral computer, therefore digital large format is much more likely to be used in a studio setting than its analogue counterpart.

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