Bridge digital camera
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This article is about a class of live-preview digital cameras. For a definition and general information on live-preview digital cameras, see Live-preview digital camera. For a comprehensive treatment of all categories of digital cameras, see Digital camera.
Bridge or "prosumer" digital cameras are high-end live-preview digital cameras (LPDs). They are comparable in size and weight to the smallest dSLRs but are non-dSLRs because they lack the mirror and reflex system that characterize dSLRs. The word bridge refers to the fact that they occupy a niche between compact digital cameras and dSLRs. The word prosumer emphasizes their high-end and advanced features which distinguish them as prosumer cameras from the consumer compacts, but with no clear-cut line. The two classes (bridges and compacts) together form the LPD category and thus share some basic characteristics (mainly a live-preview on an electronic screen as their principle means of previewing and framing before taking a photograph). Pay special attention to the bridge camera section in the Digital camera article mentioned above.
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[edit] Non-essential characteristics
The introduction above gives a basic definition which applies to all bridge cameras. There are also other non-essential characteristics which apply to a great majority but not necessarily to all bridge cameras. For example, the existence of one single fixed (non-interchangeable) lens and a CCD sensor that is much smaller than the sensors of dSLRs (which have 4/3" and larger, [1]), though some bridges had a slightly larger sensor (2/3") than the sensors of compact cameras (1/1.8" and smaller sizes).
[edit] Exceptional bridge cameras
A few recent models of bridge cameras like the Sony DSC-R1 and the upcoming Sigma DP1 have defied some of the non-essential characteristics above, by having sensors that are larger in size and different in type (CMOS instead of CCD) comparable in size to the sensors of some dSLRs (APS-C). Although there are currently no bridge cameras with interchangeable lenses, this may change in the near future; as there is a lot of talk about future bridge cameras called EVIL cameras (Electronic Viewfinder Interchangeable Lens cameras). The electronic viewfinder has already been implemented in many bridge cameras. What remains is simply to combine that with lens interchangeability, which is more a marketability rather than a technology challenge. Digital rangefinders like the Leica M8 and the Epson R-D1 have interchangeable lenses, are high-end and non-dSLRs; but are non-LPDs and too professional (just as highly as top dSLRs) for them to be considered bridge cameras.
[edit] One single fixed but versatile lens
When a bridge camera has a small sensor, a lens of a small diameter is sufficient. Consequently very large zoom ranges are feasible with one single lens. Long focal lengths (up to the equivalent of 436mm on a 35mm camera) can be obtained in a compact body with its fixed long zoom or ultra zoom lens. The fact that one single small-diametered zoom lens can cover a wide range of focal lengths from wide-angle to telephoto and macro; makes lens interchangeability much less needed, hence manufacturers have so far always chosen to make the lens fixed on all small-sensored bridge cameras (the two large-sensored models of the R1 and DP1 -mentioned above- also have fixed lenses but with limited focal ranges).
[edit] LCDs and EVFs as principle viewfinders in LPDs
Bridge cameras and LPDs in general employ two types of electronic screens as viewfinders: The LCD and the Elecronic ViewFinder (EVF). All LPDs have an LCD with live-preview and usually in addition either an EVF or an Optical ViewFinder (OVF) (Non-parallax-free as opposed to the OVF of dSLRs which is parallax-free). The existence of a high-quality EVF is one of the advanced features that distinguish bridge cameras from consumer compact LPDs.
[edit] LPDs (bridges) vs dSLRs viewfinder comparison
[edit] LPD viewfinder advantages
Since in LPDs there is no mirror that blocks the image formed by the objective lens from being projected over the sensor, as is the case with dSLRs; the LCD and EVF of LPDs continuously show the image generated by the sensor. This continuous digitally-generated live-preview is the main characteristic of LPDs and has some advantages and disadvantages over the optically-generated view through the OVF of dSLRs. One advantage is that the digital preview is affected by all shooting settings and thus the image is seen as it will be recorded (in terms of things like exposure, white balance, grain-noise...etc, which the OVF of dSLRs is totally unaffected by and so incapable of showing. Another advantage is facilitating the framing from difficult angles by means of making the LCD movable (vari-angle). Also the LCD and EVF show 100% of the image while previewing (WYSIWYG), while the OVF of some dSLRs (especially cheap dSLRs) does not cover full 100% (just few percentage points less).
[edit] LPD viewfinder disadvantages
The disadvantages however are that the electronic screens of LPDs, do not work as well as the OVF of dSLRs in situations of low light (or in bright day-light with the LCD), where the screen might be difficult to see and use for framing. Also the screen is of low resolution and refresh rate compared to the infinite resolution and instantaneous refresh of the OVF of dSLRs. The low resolution makes it less easy to focus manually but most modern bridge cameras implement a method that automatically magnifies a central frame within the screen (manual focus point). A slow refresh rate means that the image seen on the screen will have a fraction of a second lag or delay from real scene being photographed. Anyhow the electronic screens used in modern LPDs are getting gradually improved in their size, resolution, visibility, magnification and refresh rate (bridges in particular are better than compacts in this respect).
[edit] Examples of bridge cameras
Current examples of bridge cameras are the Panasonic Lumix DMC-FZ50, the Fujifilm FinePix S9000, the Kodak EasyShare P880, the Sony DSC-R1, the Sigma DP1. Manufacturers like Canon, Nikon and Olympus have stopped making high-profile bridge models preferring to concentrate on producing cheap consumer dSLRs (some of which made of plastic instead of the usual magnesium alloy used for high quality dSLRs).
[edit] Bridge cameras endangered and face unknown future
The consumer dSLRs are in fierce competition with bridge cameras due to the overlap in the price and size of the two categories [2]. The last and best-known bridge models from Canon, Nikon and Olympus (the PowerShot Pro1, the Nikon Coolpix 8800 and the C-8080 Wide Zoom respectively) were all made in 2004, all are now discontinued without replacements and all were made with a sensor (2/3") relatively larger than what is commonly used by other bridge camera manufacturers today (1/1.8").
The future of bridge cameras will depend on how successful they can be in competing with consumer dSLRs and on the materialization and viability of the future EVIL design.
