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Single lens reflex (SLR)

tranworld (dpreview, Panasonic forum, 9 March 2004)...

SLR means a Single Lens Reflex. This term was invented to designate camera that were different from a DLR, Dual Lens Reflex, the archetypical Roleiflex of the time. The Rolei also offer a reflex type of viewing, that is the image is projected onto a screen via a 45 degree mirror, but it does so via 2 separate lens, one for the viewing the other for the sole purpose of taking the picture. Do not confuse DLR with rangefinder camera where the viewing optic is a different window and there is no reflex viewing.The problem with this is the slight parallax problem when taking picture of close subject, as the viewing lens is above the picture lens a slight difference exist if you are close enough.

So when the technology advances and manufacturers were able to create a camera that allow the viewing AND picture taking via the same lens, the term SLR was born. Incidentally they did so by a system of mirror that flip up and down just before taking the picture. Now that there is only a single lens, one could easily change the lens to afford a different viewpoint.

This is where things gets a bit muddled, the term SLR is then conventionally used to indicate a camera with single lens and reflex viewing AND changeable lenses. Having said that, many years ago, Ricoh released the Mirai and this was an SLR with a built-in x4 zoom (not changeable).

So if you refer to the original spirit of the word, i.e. a camera that allow{s} you to see exactly what you are taking through the same lens, then the FZ10 qualifies as an SLR (so do most digital cameras), but if you refer to the letter of the word then the FZ10 does not as it does not offer ``reflex'' style of viewing (and no changeable lens).
Other than `through the lens (TTL)' viewing, I typically expect an SLR to offer an optical view of the image passing through the lens (and ultimately onto the film or digital capture device). Admittedly this is not really in the definition of `SLR'. However, camera manufacturers who claim that their camera is a `digital SLR' usually have an optical viewfinder, rather than an electronic viewfinder (EVF).

One day electronic viewfinders may be as good as optical viewfinders (and perhaps an electronic viewfinder might offer bonuses, such as additional information and night-vision). Currently, however, electronic viewfinders offer low resolution, poor contrast and usually low brightness compared to an optical viewfinder. Electronic viewfinders have the advantage of showing what is really happening on the digital sensor.


next up previous index Link to 'photography' page
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David Fong 2009-09-04