Panasonic GH1 Super High-Res Electronic Viewfinder

The Panasonic GH1's electronic viewfinder is identical to the G1's, which set a new quality standard for EVFs in digital cameras. The keys to the Panasonic GH1's exceptional EVF performance lie in two technologies. First, the active element of the display is an LCOS (liquid crystal on silicon) chip. This technology actually controls the state of the liquid crystals with electric fields projected through the silicon. This means that all the active circuitry can be on the back side of the chip, so the entire display surface is active: With no dead areas between pixels, light is reflected from the entire surface, so there are no distracting black areas surrounding each pixel.

Because the LCOS chip is reflective, you generate an image by bouncing light off its surface, rather than by passing light through it as in a conventional transmissive LCD. It turns out that LCOS chips can also change states very rapidly; fast enough that you can display the red, green, and blue color channels in very quick succession with no blurring or crosstalk between the color channels. Human persistence of vision blends these together into a single pixel displaying a full range of color. Looking into the Panasonic GH1's EVF then, you don't see individual red, green, and blue stripes or dots -- there is no grid -- you just see a surface of continuous color, which looks more like an optical viewfinder. To be fair, this isn't a new innovation with Panasonic: The original Minolta A1 digicam used similar technology, but its EVF had much lower resolution, and considerably lower image quality overall. The concept has certainly been seen before, but the Panasonic G series' EVF takes the technology to another level.

Light for the GH1's EVF comes from a trio of red, green, and blue LEDs: They strobe on and off in very quick succession (180 times a second, for a 60 frames/second overall refresh rate), as the LCOS chip displays the red, green, and blue image planes in lock-step. I expected to see some tearing of the display, or perhaps a rainbow effect if the subject moved rapidly, but actually saw very little evidence of this.

The second key technology in the Panasonic GH1's EVF is a holographic diffraction grating that's curved above the LCOS chip. This optical element reflects the RGB light from the LED array onto the LCOS chip's surface, but lets the light reflected from the imaging chip pass through unobstructed, out the eyepiece and to the user's eye. Other technologies could be used to make a reflective imager work in a viewfinder, but the holographic grating allowed Panasonic's engineers to squeeze the whole assembly into an incredibly compact package.

As befits its heritage in the high-end broadcast TV field, the Panasonic GH1's EVF has impressive specs. It has unusually high resolution for a camera EVF, displaying 800x600 (SVGA resolution) full-color pixels. (A total of 480,000 full-color pixels.) Panasonic equates this with 1.44 million dots in a conventional display, as most displays would need three separate dots for each full-color pixel. In practice, the effective perceptual equivalent of 480,000 full-color pixels is more like 960,000 RGB dots, but the fact remains that this is a very high-resolution, very smooth-looking display. As noted above, the GH1's EVF also refreshes at 60 frames/second, so there's very little flicker or tearing with moving subjects.

Thanks to its LED illumination, the Panasonic GH1's EVF also has a very wide color gamut, covering 100% of the NTSC color space, an unusually broad range for a camera display. As you'd expect, it also covers 100% of the field of view of the camera, since it's getting its image directly from the camera's image sensor. Finally the EVF's optics give an effective magnification of about 0.7x relative to a 50mm lens on a 35mm camera. This is about the same viewing magnification as is found on most higher-end SLRs. In practical terms, it means that with a 35mm lens attached (roughly equivalent to a 50mm lens on a 35mm camera), the image in the viewfinder will match what you're seeing through your other eye. This makes it easier to shoot with both eyes open, so the eye not looking through the viewfinder can give you much better peripheral vision of subjects about to come into the field of view, etc. The viewfinder also offers a generous diopter adjustment of -4 to +4, adjustable via a dial to the left. Infra-red sensors just to the right of the eyepiece are used to detect when an eye is moved close to the viewfinder, to automatically switch between the LCD monitor and viewfinder. An LVF/LCD button to the left of the eyepiece can also be used to switch manually.

 

Panasonic GH1 Full-time Live View

By its nature, the Panasonic GH1 is always in "Live View" mode: In that respect, it's like any point & shoot digicam with the combination of an electronic viewfinder and rear-panel LCD that works as a viewfinder as well. The differences with this camera are that it has interchangeable lenses, focuses a lot faster than the average digicam, and has a larger sensor to provide better low-light performance than typical pocket cameras.

To their credit, though, Panasonic seems to have made more of an effort in the Lumix GH1 to have the viewfinder display accurately mimic what you'll see in the final image file once you've snapped the shutter. They seem to be trying to go the point & shoot market one better with their viewfinder display accuracy and simulations, and they seem to be succeeding.

The shots above show two options the camera gives you for viewing your subject in record mode. On the left, the subject fills a larger area of the display, but the exposure information is overlaid on the bottom of the image. This gives more image area, but potentially makes the exposure info a bit harder to read. As seen on the right, you can instead opt for a smaller view of the subject, putting a sharply contrasting black background behind the exposure readouts, making them easier to see. The shots above show the display on the rear-panel LCD; the information overlay on the EVF screen is considerably less extensive. (See the Operation tab of this review for illustrations and callouts describing the information shown on the various displays.)

The Panasonic GH1 features a live histogram display with a nifty trick: you can select to have it displayed or not, and you position it pretty much anywhere on the display screen that you like. In the screen shots above, I've put it in the lower right corner. There are three grid options available as well, including one that is customizable.

 

Panasonic GH1 EVF & LCD User Experience

We have never been particular fans of EVFs over conventional optical viewfinders. Part of this has to do with the relatively low resolution of past EVFs, an issue that the EVF in the Panasonic G1 and GH1 addresses rather decisively. Resolution only accounts for part of our dislike though; the other part is dynamic range, or contrast ratio, to use the term more commonly associated with electronic displays. It's been our experience that electronic viewfinders generally do a poor job of holding detail in highlights, shadows, or both. We've often been frustrated when trying to compose landscape shots that contained important cloud detail with EVF cameras: Areas of clear sky and clouds were often indistinguishable from each other. At the other end of the tonal scale, detail in shadows has often been difficult to pick out.

The viewfinder in the Panasonic GH1 seems to do a better than average job at the highlight end of the tonal scale, but we often found detail lacking at the shadow end of the scale. Looking into the EVF, dark areas of the image never became truly black. The effect was similar to what we remember seeing on early model LCD televisions, where the blacks just weren't very black. Of course, the GH1's live view circuitry amplifies the signal from the sensor whenever you're viewing a dimly-lit scene, so you can see what's going on pretty well, even you're shooting in rather dark surroundings. That's not the issue, though. Where we had trouble seeing what was going on was in situations where there were both bright and dark portions of the scene, and where there was important shadow detail we needed to see in order to frame properly, but these areas were too dark. There'd be good detail visible down to a certain brightness level, but beyond that would be nothing but a dark grey. We first noticed this with the GH1's EVF, but the effect is present (albeit to a somewhat lesser extent) in the rear-panel LCD as well.

In writing about this, while we noticed a lack of detail in shadow areas in the Panasonic GH1's EVF, we realized that we'd not made this a focus of our testing and analysis in the Live View SLRs we've tested to date. In the interest of fairness, we took a quick look back at some of the Live View SLRs we had around the office, to see how much of an issue this is with other cameras. What we found surprised us: There was a wide range of behavior in various cameras' Live View displays, and camera price wasn't at all an indicator of performance in this area. Some of the most expensive cameras showed only so-so shadow detail, while some relatively inexpensive cameras produced very clear displays.

Overall, Olympus was the big winner in the shadow-detail derby, as its cameras appear to selectively boost the image amplification in large, dark areas of the frame, while leaving brighter areas untouched. The result is very clear (if a little noisy) shadow detail, even when other parts of the image are very bright. Most other cameras we looked at (Canon 50D, Nikon D300, D700, Sony A350) didn't seem to adjust image brightness dynamically, and the GH1's LCD actually showed a bit more shadow detail under similar conditions than the Canon, Nikon, and Sony cameras. The GH1's EVF showed considerably less shadow detail than either its LCD screen or the LCD screens of the competing SLRs.

So the bottom line on the dynamic range of the GH1's viewfinders is a bit of a mixed bag: The LCD shows better than average dynamic range and shadow detail, while its EVF shows less than average. The good news is that you have the option of switching to the LCD if you really need to frame for the shadows.

Also worth considering is that it's harder -- if not impossible -- to track a moving subject with either the LCD or EVF. Once you start shooting in Continuous mode, the Panasonic GH1 does not return you to a Live View of the scene as does an SLR's optical viewfinder; instead, you're given a brief flash of the last image captured, which doesn't help you track at all. This is a limitation of all current live view systems, SLR or not.

Regardless, while we prefer an optical viewfinder, Panasonic's advanced technology offers users the best alternative that's ever been made available to still photographers in the GH1 (and G1).