Live preview

In digital photography, live preview is the feature that allows a digital camera's electronic display to be used as a viewfinder, that is, as a means of framing and previewing before taking the photograph. In most such cameras, the preview is generated by means of continuously and directly projecting the image formed by the objective lens onto the main image sensor, which in turn feeds the electronic screen with the live preview image. The electronic screen can be either a liquid crystal display (LCD ) or an electronic viewfinder (EVF).

Historical background

While some types of digital cameras trace back their origin to a corresponding type of film still cameras (for example digital single-lens reflex cameras "DSLRs" to film single-lens reflex cameras "SLRs"; digital rangefinders to film rangefinders, etc.), cameras with live preview also derive from electronic (video) TV cameras.

Most early digital cameras through 1995 did not have a live preview; most digital single-lens reflex cameras still do not have this feature, as it is fundamental incompatible with the single-lens reflex mechanism. The first digital still cameras with an LCD display and live preview were the Casio QV-10 and Ricoh RDC-1 in 1995.

Compacts & bridges, the low- and high-end cameras with live preview

Live-preview cameras include two different but not so distinct categories: Bridge digital cameras and Compact digital cameras. Bridge cameras in general are higher-end and more advanced (feature-packed), expensive (higher build quality) and sizable than the compacts.

Testing

DSLRs, cameras usually without live preview

When considering the advantages and disadvantages of DSLRs, the comparison is usually made between the best bridge cameras, and the smallest and cheapest DSLRs, so most of what can be said in this respect is treated in the bridge camera article. Check in particular the following sections in that article:

• One single fixed but versatile lens
• LCDs and EVFs as principal viewfinders

A comparison between compacts and DSLRs would be really a very contrasted one in terms of size, weight, price, capabilities and image quality.

Almost all modern bridges and compact cameras have a movie mode, while no DSLR has so far offered this option. DSLRs, on the other hand, have a faster performance than other cameras in many areas (for example, start-up time, shutter lag, continuous mode, autofocus...etc). This means that DSLRs are more reliable in situations, such as sport or action photography, where being late for a fraction of a second may result in missing the right moment of taking the picture. The idea that DSLRs perform better than other cameras in high ISO settings has to do primarily with the sensor size of the camera, not whether it has live preview. DSLRs always have large sensors while a great majority of other cameras have a small sensor (notable exceptions being the Sony R1 and the Sigma DP1).

Digital SLRs with live preview

Live-preview functionality is becoming more and more common on digital SLR cameras, and as of mid 2008 almost all new DSLRs have the feature. The following is a partial list of DSLRs with live preview:

• Canon EOS 20Da
• Canon EOS 40D
• Canon EOS 450D
• Canon EOS 1D Mark III
• Canon EOS 1Ds Mark III
• Leica Digilux 3
• Nikon D300
• Nikon D3
• Olympus E-330
• Olympus E-410
• Olympus E-420
• Olympus E-510
• Olympus E-520
• Olympus E-3
• Panasonic Lumix DMC-L1
• Panasonic Lumix DMC-L10
• Sony Alpha A300 and A350
• Pentax K20D
• Samsung GX20

Live preview in some or all of these cameras is not conventionally generated (the image formed by the lens is either not directly or not continuously projected over the main sensor). Also the live preview in these DSLRs does not typically serve as their principal means of framing and previewing before taking a photograph. (As DSLRs, they have an optical view reflected in the OVF (Optical Viewfinder) for that purpose and the live preview is an additional feature).

While live-preview technology has been advancing, as for March 2008, there are no DSLRs which show a live preview as seamlessly as a fixed-lens camera. The main issues are with slow focus and lack of exposure-priority display. Among the DSLRs that do manage to focus using the standard phase-detection sensor used by DSLRs, none has managed to show 100% frame coverage like conventional digital cameras, thereby removing the key advantage of live preview over optical viewfinders. Additionally, 100% coverage optical viewfinders have recently become more common and affordable with the appearance of the Nikon D300 and Olympus E-3.

Digital camera backs with live preview

Phase One

• P20+
• P21+
• P25+
• P30+
• P45+
• P21
• P30
• P45

See also

• Digital single-lens reflex camera
• Photography
• Digital photography
• Still camera
• Digital back

External links

• Evolution of Live Preview in Digital Photography.