Live-View Advancement

2007.09.03

After the Olympus E-10 and E-20 were long forgotten, the preview display on the rear LCD of DSLR cameras is continuing its comeback. Although, the Fuji Finepix S3 Pro's black-and-white 30 second preview was wisely ignored, it was Olympus which revived the trend with its E-330 DSLR. Now Canon, Nikon, Olympus and Panasonic are all working to improve the preview capabilities of digital SLR cameras.

Olympus called this feature live-view and the term is being reused by other DSLR manufacturers. The ideal live-view would be a true WYSIWYG representation of the image about to be captured. Specifically, the ideal live-view would:

1. Show 100% of the photograph.
2. Display an accurate representation of the chosen exposure, including the effect of applying exposure compensation.
3. Display an accurate representation of the chosen white-balance, including custom white-balance and white-balance fine-tuning.
4. Optionally allow stopping down of the lens to preview the depth-of-field at the chosen aperture. Note that since DOF is dependent on the print or display size, DOF-preview is rarely entirely accurate.
5. Optionally display a luminance or color histogram.
6. Allow the overlay of visual aids such as grid-lines and scales to help compose photographs.
7. Also display important camera settings: shutter-speed, f-stop, ISO, exposure-compensation (or estimated exposure-deviation in manual exposure mode), metering mode, white-balance and exposure mode (P,A,S,M,etc), shots-remaining, battery-level, etc.
8. Accurately represent the chosen focus distance.
9. Optionally allow zooming in on part of the preview to validate focusing.
10. Allow automatic exposure to be continuously evaluated.
11. Allow all autofocus modes to work accurately without disrupting the preview.
12. Do all of the above with minimal display and shutter lags.

Among advanced fixed-lens digital cameras, the above points have all been met before, staring a few years ago with the Konica-Minolta Dimage A2 which was the first fixed-lens camera with a DOF-Preview function. Now, with the exception of DOF-preview, most fixed-lens digital cameras have such previews. That is commonly referred as having an exposure-priority preview. Some cameras such as the Sony Cybershot DSC-R1 allow switching between exposure-priority and display-priority previews.

Among DSLR cameras, the situation is quite different. First, most DSLR cameras do not feature any preview at all. The Olympus E-330 has two previews, each satisfying some of the above points. One preview mode shows 100% frame coverage but disables autofocus, while the other shows 92% of the frame but allows normal autofocus. It turned out that having two modes was confusing and not showing 100% coverage destroyed one of the main advantages of having a preview display. The result is that all other DSLR cameras with live-view only have a single mode which shows 100% coverage.

The latest DSLR cameras from Nikon, the not-yet-available D3 and D300, are the first ones to feature a live-view with autofocus using the camera's imaging sensor. At the time of their availability, these cameras are expected to satisfy more of the above points than any other DSLR. The Panasonic Lumix DMC-L10 was also announced to allow live-view with autofocus but will not have a DOF-preview function. Since neither of these cameras are currently available, it will be some time before we know how usable their live-view is.

Obviously, having a true exposure-priority display is a desirable feature to have on a DSLR and progress is being made in that direction. Succeeding at correctly implementing this would make DSLR cameras as easy to use as most prosumer fixed-lens digital cameras. This would accelerate the adoption of DSLR cameras among users of fixed-lens cameras.

Note that because there is no total solution, no one has tried to produce a DSLR without a reflex viewfinder. Actually that is an oxymoron because a DSLR is defined by its reflex viewfinder. A DSLR without a reflex viewfinder would simply be a large-sensor digital camera with interchangeable lenses. There are probably many consumers who would be satisfied with having the flexibility of interchangeable lenses in a lighter and quieter camera. Removing the pentaprism and mirror would achieve both these goals at once. Hopefully such a camera would be equipped with a high-resolution EVF so that it can be held more steadily and discreetly at eye-level rather than at arms-length.

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