Direct vision viewfinder

This is an optical viewfinder which doesn't show the view through the camera lens but is lined up with it so that it's as close as possible to what the camera will see.

They work very well on cameras with fixed focal length lenses, including Leica's rangefinder cameras and Olympus's E-series Pen cameras when the fixed focal length 'pancake' lens is used in conjunction with the optional viewfinder accessory.

Their advantages are they they provide an extremely clear, bright image which may be superior even to that of a digital SLR's, and because they show what's outside the frame as well as within it, many photographers find they make it easier to keep up with fast-moving subjects and anticipate picture-taking opportunities.

Disadvantages include the lack of any kind of focussing ability (except with rangefinder cameras), a degree of optical distortion and some framing inaccuracy, especially with nearby subjects.

And although they work well on more expensive cameras with fixed focal length lenses, they're less successful on compact cameras. Here, they have to use a zooming mechanism to stay aligned with the camera's own zoom setting, and the result is very small, cramped viewfinders with lots of distortion and poor framing accuracy.

EVF | Electronic viewfinders have cons as well as pros

Electronic viewfinders are used on some cameras where an optical viewfinder would be impractical or undesirable. In the past, the quality of EVFs has been pretty low, but Epson has announced a new 800 x 600 pixel screen which could help change all that.

The point about the Epson display is that it has much higher resolution than usual. Most EVFs have just 0.23 megapixels and look pretty grainy, but this one has 1.44 megapixels and should look much sharper and smoother, helped by an 'analog driver' which produces smoother colour gradations.

This new technology could be highly significant for two types of camera: superzooms and hybrid D-SLR replacements.

Digital compact cameras with long-range zoom lenses, like this Nikon P90, cannot be fitted with optical viewfinders because they do not have an SLR viewing system, and the zooming range is too great for a separate, linked viewfinder. Instead, you get a second, smaller LCD display which you see through the viewfinder eyepiece. This is basically another, smaller LCD, just like the one on the back. Usually, the resolution is too low for accurate focussing or examining fine detail.

The other application for high-resolution EVFs is in hybrid D-SLR replacements like the Panasonic Lumix G1, above. Although it looks like an SLR, the G1 has no mirror. Here, you can see straight through to the sensor itself. During normal viewing, the image is formed on the sensor and transferred either to the LCD on the back or to the electronic viewfinder.

EVFs allow cameras to be smaller, more sophisticated and yet mechanically simpler. There are some serious drawbacks to EVFs, though, which affect the relative strengths of hybrid cameras versus D-SLRs:

• Even the latest high-resolution EVFs lack the visual clarity of an SLR's optical viewfinder

• EVFs consume much more power than optical viewfinders, which usually have a few status LCDs

• Conventional optical viewfinders get their illumination from the subject itself, so their brightness always matches the conditions. EVFs, however, can get swamped in very bright light or prove overpowering in dimmer conditions, even with automatic brightness adjustments