Zalman Trimon ZM-M220W Stereo Monitor Review

No matter how many polygons or light sources contemporary graphics cards can create in a single frame, the real world has one principal difference from the virtual world: it is truly 3-dimensional. Luckily, the situation is not hopeless. Meet the new stereo monitor from Zalman that changes it all.

by Oleg Artamonov
09/18/2008 | 03:43 PM

Talking about the future of 3D graphics on the personal computer, some people argue that the picture displayed by the monitor can be as detailed as to be indistinguishable from reality provided there are enough polygons and light sources per frame. Alas, it cannot. I don’t mean this level of detail is impossible. The real picture just has one important difference. As opposed to the monitor’s screen, it is three-dimensional. Until we manage to produce a 3D picture on the computer monitor, telling it from reality won’t be difficult.

 

The situation isn’t hopeless, though. Today I am going to introduce to you the Trimon ZM-M220W monitor from Zalman that can produce a truly 3D picture.

I’d like to dwell upon the theory and history of the problem first.

We have three-dimensional vision, i.e. the ability to estimate the distance to the objects we see, thanks to our two eyes. Each eye sees the object from its own point of view, and the brain compares the two pictures and calculates the distances basing on the differences.

So, in order to “deceive” our eyes and make them see the third dimension on the monitor’s two-dimensional screen it is necessary to provide an individual picture for each eye.

The direct way to achieve this is to wear eyeglasses (or a Virtual Reality helmet) with two small displays opposite the eyes. This is a universal but technically complex solution. The whole contraption is too bulky and heavy and it is hard to make the displays small yet with a high resolution. As a result, such helmets either have a resolution of 640x480 or cost enormous money (there are exceptions that combine both these drawbacks in one device).

A simpler way is to make the monitor display two pictures, for each eye, and use eyeglasses to separate them.

The classic and well-known solution is to use colored eyeglasses, for example with red and blue glasses. A 3D picture prepared for such eyeglasses contains two images, for the left and right eye, but one is red and another is blue. Such a picture doesn’t look appealing when viewed with a naked eye:

But the blue lens prevents the corresponding eye from seeing red whereas the red lens prevents the other eye from seeing blue. As a result, each eye sees only the picture it is meant to see, which helps achieve the 3D effect.

The drawback of the two-colored glasses is obvious. There is no talking about color reproduction when you use them. Although such stereo-pictures can be colored, their colors are dull and unexciting.

A more sophisticated method involves using eyeglasses with LCD shutters instead of the lenses. The shutters are being closed and opened alternately. This technology doesn’t work for static pictures but works for movies: all the odd-numbered frames must be prepared for one eye and all the even-numbered frames, for the other eye. Syncing the moments of the opening and closing of the shutters with the alteration of the frames, we can make each eye see only those frames that it is meant to see.

This technology has no color reproduction limitations but has others instead. First, each eye sees only half the frames with rather long intervals in between, so the frame rate must be high enough for the eye not to notice the flickering. Second, the glasses must be strictly in sync with the alteration of the frames. Otherwise the picture will lose the 3D effect and divide in two. If the eyeglasses are used together with an LCD monitor, there is a third problem: the matrix’s response time must be low enough for adjacent frames not to merge into each other.

As the consequence of these limitations, such eyeglasses were produced for a while but didn’t really take off.

However, an LCD monitor has one special property due to the very technology of producing an image by means of liquid crystals. It is an inherent but rarely mentioned property. An LCD monitor yields polarized light. Take any polarizer (e.g. an appropriate filter for your camera) and look through it at any LCD monitor: you will be changing its transparency from zero to maximum by simply turning the filter around.

Can this be of any use, though? A filter will block all light from the screen, just like the above-mentioned eyeglasses with shutters. Yes, it will – with an ordinary monitor. But the monitor’s screen can be divided into zones with different polarization of light. This can be achieved by means of two polarizer films placed on both sides of the liquid crystals. Now if we take a look through a polarizing filter, some zones will look darker and others lighter depending on the position of the filter. If we take two filters, one for the left eye and the other, rotated by 90 degrees, for the right eye, one eye will see some zones on the screen and the other eye will see different zones!

If the different-polarity zones are small enough and distributed uniformly on the screen, each eye will see the whole picture, these pictures will be different!

So, here they are: the Zalman Trimon ZM-M220W monitor and the polarizing eyeglasses.

I guess the point of the technology is obvious from this photograph: the odd- and even-numbered lines of pixels of the monitor’s screen have different directions of light polarization. But the human eye itself doesn’t perceive polarization. Without special eyeglasses, you just see an ordinary image.

The lenses of the eyeglasses are polarizers whose polarization planes are rotated relative to each other. So, you can see odd-numbered lines through one lens and even-numbered lines through the other lens. If the monitor shows a stereo-picture in which the image for one eye is shown in the odd-numbered lines of pixels and for the other eye in the even-numbered lines, each eye will only see the picture meant for it.

Take note that the eyeglasses are a passive device here (they do not contain any electronics and do not need to be in sync with the monitor) and do not distort color reproduction.

This can be illustrated by the picture from the Zalman website.

There is only one thing that I haven’t mentioned: there is an additional film on the LCD matrix that transforms linear polarization of light into circular. This prevents the picture from getting distorted when the position of the eyeglasses relative to the screen changes.

The obvious drawback of this technology is that the effective vertical resolution of the monitor is reduced twofold. If the screen has a native resolution of 1680x1050 pixels, each eye will only see 1680x525. Anyway, this is a far higher resolution than what you can get with a VR-helmet. It is quite appropriate for games and movies.

Closer Look at Zalman Trimon ZM-M220W

Apart from its ability to deliver a three-dimensional picture, the Trimon ZM-M220W is no different than other 22-inch monitors. It is based on a TN matrix without response time compensation, has a native resolution of 1680x1050 pixels, viewing angles of 160 degrees, and a maximum brightness of 300-400 nits. That’s not a typo – the Zalman website isn’t certain about the precise number.

The monitor surprised me with its neat and even austere appearance. When I was unpacking it, I was expecting to see a traditional realization of the designer’s notion of a gaming or luxurious monitor which would involve chrome details, blue LEDs, etc. The Trimon resembles a good work-oriented monitor instead. It has a matte black case with no decorations. It is neat, modest and understandable.

The designer couldn’t suppress himself in one thing only. The matrix has a glossy coating here. This increases contrast and saturation but also produces flares as the photographs shows. I don’t have any tools to evaluate the reflective capacity of the monitor’s screen, but it seems to be the most mirror-like monitor I’ve ever dealt with.

The monitor has a handy and functional stand, which is untypical for home/gaming models, too. It allows to adjust the tilt and height of the screen, pivot into portrait mode and turn the screen around the vertical axis.

When turning around the vertical axis, the bottom part of the stand remains motionless: the hinge is in the place of the fastening of the monitor’s case to the stand.

The height adjustment can be blocked with the screw at the bottom of the stand for easier packaging and transportation. Otherwise the stand would stretch out when you pick the monitor up from the desk or out of the box.

The monitor’s native stand can be replaced with a VESA-compatible mount, for example to hang it on a wall.

We’ve got a standard selection of connectors here: analog and digital video inputs, a line audio input for the integrated speakers and a headphones output. There is no HDMI input but you can buy a HDMI → DVI adapter if you need it.

The monitor’s controls are located on its right edge and labeled on the front panel. The buttons are rather small but handy. They are placed sufficiently far from each other so that you didn’t miss the necessary button.

Quick access is provided to the automatic adjustment feature, to the sound volume and mute settings, to switching between factory-set modes (MWE button) and between the inputs (Mode button).

The onscreen menu is neat and user-friendly. It doesn’t offer any special setup options.

The separate menu evoked with the MWE button offers a number of factory-set images modes for various applications such as work, games, movies, etc. Such presets are offered by many modern monitors. Later in this review you will see how they are set up in this model.

3D Performance

I have explained above how the monitor can produce two independent pictures for the left and right eyes on the hardware level. Of course, this requires software support. The graphics card must process both frames simultaneously and combine them together in interlaced mode: the odd-numbered lines come from one frame and the even-numbered lines come from the other frame.

So far, this is not a default function of any graphics card. Nvidia has been doing some work in this field but only offers such technology in GeForce 6 or higher series cards and only for 32-bit versions of Windows Vista. Such drivers had been developed for Windows XP and 98 but the support for these OSes was abandoned. The owner of a Trimon will have to install Windows Vista.

Eyeglasses with polarizing lenses are included with the monitor, of course. They do not feature an extraordinary design, yet they are handy and should be appreciated by the fans of Half-Life. Gordon Freeman wears the same eyeglasses (without the Zalman logo, though).

These eyeglasses do not have any diopters but if your eyesight isn’t perfect you can use the included clip-on lenses that can be attached to ordinary eyeglasses.

These lenses aren’t very convenient. Their fastening will be annoying if the frame of your eyeglasses fits tight to the bridge of your nose. They also make the eyeglasses much heavier. On the other hand, these drawbacks can be put up with. I can assure you about that because I wear eyeglasses, too. If you need to distract from your play for a couple of minutes, you can just lift the clip-on lenses up without taking them off.

Included into the kit are a plastic case for the glasses and a microfiber napkin for cleaning them. Do not forget to remove the protective film from both sides of the lenses prior to wearing them.

I performed my tests on a computer configured like follows:

The monitor doesn’t need additional drivers. The included disc contains the same 3D-stereo driver from Nvidia.

The driver was installed without problems. After the installation, there appeared a Desktop icon of its control panel. The 3D-stereo driver has its own control panel that does not overlap with the one of Nvidia’s ordinary graphics card driver. Besides setup options, the control panel offers a good test of the 3D mode.

One of the most important options of the Control Panel is the Depth Amount slider which refers to the depth of the emulated 3D space. If you feel a headache or have difficulties focusing on the image in the stereo mode, you should try to reduce the spatial depth. If, on the contrary, the image seems too flat, try to increase it.

You can see two buttons that launch 3D tests here. The Medical Test Image button opens a window with text and an object. Without the polarizing eyeglasses this looks like a square chaotically filled in with black dots. In the eyeglasses, if the monitor is set up correctly, you can see a second square which is placed against the first one but closer to you. It seems to be hanging in front of the screen as if you can touch its corner with your finger.

You can find the optimal position of your head relative to the screen using this test. As I found out, the ZM-M220W gives you a lot of freedom in choosing your head position. The 3D picture remains in fact the same if you move your head around a little. However, the screen must be placed in such a way that your eyes were opposite its center. The 3D picture splits up if viewed from above.

The Launch Test Application button launches a program that shows a simple picture: Nvidia’s logo is rotating and floating back and forth within a tunnel.

The picture is so three-dimensional that you get a feeling the logo is just sticking out of the screen. But as soon as you take the eyeglasses off, you only see a fuzzy and stirring jumble of lines.

The second tab of the control panel offers three settings. You may only want to change the last option which disables full-screen antialiasing. If you choose a resolution other than the monitor’s native one, you’ll see a jumble of lines instead of a 3D picture even in the eyeglasses.

The next tab allows you to specify hotkeys for enabling/disabling and changing 3D mode settings right within a game. You can also turn on the so-called laser sight. As opposed to the default sight in games, this one is rendered basing on the spatial depth. Alas, this sight is often drawn along with the game’s default sight, which isn’t good. You have to turn it off then.

There is an Anaglyph Stereo button here: besides special monitors and polarized eyeglasses, Nvidia’s driver supports two-colored eyeglasses I described at the beginning of the review.

The last tab offers a long list of games that have been tested for compatibility with the 3D stereo mode. Alas, some of them are not 100% compatible. Some objects may prove to be flat or the spatial depth may be inadequate, etc. There are two values describing each game in the list. The list is far longer than what you can see in the PDF file with a description of the stereo mode available on Nvidia’s website.

After I had played with the settings and watched Nvidia’s logo floating out of the screen, I decided to check a few real-life applications on the monitor.

I found a video player and a special 3D clip about submarine life on the disc included with the Trimon. The making of the clip was simple: it is in fact two AVI-files recorded at somewhat different points of view while the player combines them into a single picture.

The viewing of the clip was interesting indeed. The image does have the third dimension. The fish, corals and other see-dwellers swim out of the monitor right into your hands and then move away into the depths of blue water. Then, it is unusual to refocus your eyes while sitting at the monitor. The image is three-dimensional and the brain is at first fighting against the fact that you have to focus your eyes, not only move them about, to see who’s there in the corner.

There is a negative impression, though. It turned to be rather tiring to watch the clip in which there were too many objects near me. Although medium-distance and distant objects look perfect, it is somewhat difficult to focus on closely located ones. This problem can be partially solved by the control panel options. It may also be due to the specifics of the recording of the particular clip.

As for video games, the situation is different in each particular one. You experience may vary dramatically, from non-operating stereo mode to a perfectly detailed depth of space.

I couldn’t enable the stereo mode in Prey. In S.T.A.L.K.E.R. the stereo mode worked badly. There was no depth in open scenes while in closed environments the nearby objects would be seen double. I couldn’t focus my eyes on them.

Far Cry was a success. The stereo mode worked perfectly in that game. I could see three-dimensional bushes, houses, trees and cars in detailed perspective. Considering that open scenes are overall good and detailed in Far Cry, playing in the true-3D world was a real pleasure. I wouldn’t say the third dimension made a revolution in my experience of the game, but the virtual world seemed less appealing when I turned the third dimension off.

The only problem I had in Far Cry was the above-mentioned Laser Sight. I had to turn it off because it would be drawn along with the game’s native sight (and these two sights would be at different distances from me in the 3D world).

Moreover, the stereo mode affected the speed of the game. Although the vertical resolution of the frame is reduced twofold, the graphics card has to process two frames simultaneously (from two different angles) and then display them in sync. As a result, the frame rate dropped from 120-140fps in ordinary mode to 45-50fps in the stereo mode.

Another performance-related problem is that the 3D stereo mode works in the monitor’s native resolution only. Otherwise, the picture splits up. So you have to play at 1680x1050 or disable interpolation in the driver settings and agree that the image doesn’t occupy the whole screen.

I want to note that I didn’t feel a headache or sore eyes or any other unpleasant feelings after I had played for about 40 minutes. However, the user manual doesn’t recommend playing for more than 1 hour continuously. I can only add that you should turn the stereo mode off and take off the eyeglasses if you feel the game to strain your eyes (like with the doubling objects in S.T.A.L.K.E.R.). It is no good to have a headache.

So, I can’t tell you that the stereo mode has changed my life, but it has certainly made my gaming experience more realistic and exciting. Unfortunately, the stereo mode is not compatible with every game, but you can use the ZM-M220W as an ordinary “flat” monitor in case of such incompatibility.

2D Performance

A tremendous advantage of the Trimon over the VR-helmets I mentioned in the Introduction is that it can be used as an ordinary monitor. Take off the eyeglasses, disable the stereo mode – and you have a trivial 22-inch monitor with a typical resolution of 1680x1050 pixels.

I tested the ZM-M220W in the ordinary mode following our traditional methodology.

Alas, one drawback can be seen right away: the monitor’s screen is lined up horizontally with 1-pixel-width lines. This is the consequence of using polarizers and films whose polarizing properties change with each line. This is quite conspicuous: a white background on the screen of the ZM-M220W looks striped even from a distance of 50 centimeters. This defect doesn’t make the monitor totally unusable, yet it is conspicuous.

The monitor’s Brightness and Contrast settings are both set at 50% by default. The brightness is regulated with the matrix rather than with the backlight lamps, so you should better leave it at 50%. Otherwise you will lose either darks (at lower values of Brightness) or lights (at higher values of Brightness). I achieved a 100nit white by selecting 50% Brightness and 24% Contrast.

Color gradients are reproduced with barely visible banding.

The monitor’s color gamut is perfectly standard. It coincides with the sRGB color space in reds and blues and somewhat larger than it in greens.

 

The average nonuniformity of white brightness is 5.3% with a maximum deflection of 13.8%. For black brightness the average and maximum are 5.6% and 24.0% respectively. The monitor is average in this respect. You can note that the bottom of the screen is brighter than the rest of it on a black background.

The gamma curves are acceptable. They differ somewhat from each other and go lower than the theoretical curve (for gamma 2.2) in lights.

When the Contrast is reduced to 24$, the curves improve somewhat except that the blue curve still differs from the others.

The measurements confirm my subjective impressions: if the Brightness setting is reduced to 30%, darks are indistinguishable from each other. The gamma curves are nearly horizontal at the beginning of the diagram. So again, I do not recommend you to change the Brightness setting of this monitor at all.

For an unclear reason, the color temperature settings are available for analog connection only. Besides a user-defined mode, there are three modes, none of which is satisfactory. The image is rather cold even in the Reddish mode while the temperature dispersion amounts to a few thousand degrees Kelvin.

To improve this I decided to set the monitor up manually using the showings of my DataColor Spyder 3 Elite calibrator. Lowering the Contrast setting to 25% (and keeping the Brightness setting intact), I selected the following in the user-defined color temperature mode: R=67, G=50, B=30. This produced a better result as you can see in the User column of the table above. But again, you can only use this setting when the monitor is connected via its analog interface. If the connection is digital, you have to use a hardware calibrator (if you have one) or your graphics card’s driver settings.

When put on the CIE diagram, the points of gray betray the same drawback: the image is too cold and there is a big difference between the temperatures of white and gray. The monitor doesn’t deflect much into green or pink, though.

The maximum brightness is 260 nits, which is somewhat lower than the range of 300-400nits specified by Zalman. The Max column shows why changing the brightness of the screen with the matrix is bad: black becomes gray and the contrast ratio drops to a funny value. The User column shows the brightness and contrast ratio values I obtained when I had set the monitor up manually (as described above) for more accurate color reproduction.

Besides the manual settings, the monitor offers five preset modes you can select with the MWE button without entering the onscreen menu.

The modes all have a similar level of white but I have to say that you need a brightness of 80-100 nits, not 200 nits and higher, for working with text. The level of black is too high in the Movie and Smooth modes, affecting the contrast ratio negatively.

Let’s check out color reproduction in these modes, too.

The gamma curves are no different in the Text mode than at the monitor’s default settings.

The Game mode lacks lights and has oversaturated green. The resulting picture is bright and vivid but has nothing to do with accurate color reproduction.

The Movie mode is even worse: about one third of all greens are lost. You are likely to see a green smudge instead of a green field in movies. And there will be fuzzy spots in the sky instead of cirrus clouds. Besides, the contrast ratio is very low in this mode while darks become light and whitish.

Blue is the only color that is displayed properly in the Sports mode. Red and green reach the top of the diagram too soon, betraying the loss of light halftones.

The Smooth mode is hardly any different than Movie. It has whitish darks and oversaturated lights. Clouds become white smudges, and grass is a green smudge, etc.

So, the factory-set modes of the ZM-M220W are impractical as they distort color reproduction greatly. I guess you may want to set the monitor up manually for text-based applications (lowering its Contrast to 20-30% depending on the ambient lighting and keeping the Brightness setting intact). And if you need a higher brightness in games or movies, you can switch into the Text mode.

The monitor’s response time isn’t impressive: an average of 14.0 milliseconds (GtG) with a maximum of 21.5 milliseconds. This is a normal speed for a TN matrix without response time compensation but it is too slow in comparison with RTC-enabled matrixes.

Talking about the ZM-M220W in the ordinary 2D mode, it has rather mediocre setup quality. Besides, it has two technological drawbacks: the conspicuous inter-pixel horizontal lines and the locking of the color temperature setting for DVI connection.

Conclusion

The technology of producing a volumetric image by means of alternating lines and polarizing eyeglasses is undoubtedly interesting and perspective because it combines simplicity and universalism.

A stereo monitor doesn’t require advanced technologies, clumsy eyeglasses or helmets or even any additional electronics whatsoever. The hardware implementation is most elegant. I guess this solution can just be called beautiful. A small modification of the LCD matrix materials, a simplest pair of eyeglasses – and you get a true 3D picture.

A stereo monitor is no different from an ordinary monitor. VR-helmets have a very low resolution and are impractical for everyday work. Two-colored eyeglasses are incompatible with good color reproduction. The Zalman Trimon, on its part, is just a regular 22-inch monitor in 2D mode, ensuring normal color reproduction, frame rate and resolution all at the same time.

The ability to work in ordinary 2D mode is important for such devices. A VR-helmet has to be bought in addition to a regular monitor, but the Trimon can be bought instead of it! So, the cost of ownership for the Trimon is the difference in price between it and an ordinary 22-inch monitor. At the time of my writing this the Trimon cost about the same money as a VR-helmet. And there is a cheaper, 19-inch version called ZM-M190.

Unfortunately, the new technology is accompanied with drawbacks. First of all, not all games support the 3D stereo mode. It either doesn’t work or works poorly in them. This is not a fundamental problem, though. If Trimon-like solutions take off for real, game developers will have to optimize their projects for them.

Then, the monitor is not ideal in the 2D mode. But nearly all of the problems I found are the same as you can see in ordinary monitors that don’t have any stereo mode. These are setup-related problems of the particular model rather than of the 3D technology in general. It is quite possible to produce a stereo monitor that wouldn’t be inferior to ordinary monitors in terms of its setup quality in the 2D mode. I guess such monitors will be released soon.

The linearity of the image in 2D mode is somewhat alarming as it is directly linked to the interlaced polarizers that enable 3D mode. Hopefully, this problem will be solved as the technology evolves.

I do hope that stereo monitors like the Zalman Trimon ZM-M220W will soon become popular and widely available products.