Interlaced polarization is implemented in Zalman monitors to build stereoscopic images. In other words, the polarization of light emitted by the odd- and even-numbered lines of pixels is different and those lines can be filtered out by means of a simple polarizer. If you take two polarizers and turn one around and insert them into the lenses of eyeglasses, you’ll have your right and left eyes seeing only the odd- and even-numbered lines, respectively, or vice versa. Outputting two different frames for the two eyes through the odd- and even-numbered lines of pixels will give you a stereoscopic image with each eye having its own image to see.
As a matter of fact, any LCD monitor emits polarized lights but this polarization doesn’t depend on the line, column or pixel and is the same throughout the entire screen in an ordinary monitor.
Some reviews say that Zalman uses linear light polarization but this is not exactly so. Although the LCD matrix itself does use linearly polarized light, there is a special film on the exterior of the ZM-M240W’s screen which transforms linear polarization into circular one so that the image didn't depend on the angle of viewing. With linear polarization, any movement of your head would change the position of the eyeglasses' polarizers relative to the light’s plane of polarization, disrupting the separation of the 3D picture into lines.
Zalman’s approach has a number of very significant advantages:
- Extremely simple and, consequently, very cheap eyeglasses;
- No flickering (as opposed to active glasses which produce an annoying flicker at a frequency of 60 Hz);
- No serious requirements in terms of the monitor's response time (since the images for the left and right eyes are not mixed up physically, being produced by different lines of pixels, a high response time won't provoke the image doubling effect in 3D mode);
- Good brightness (Zalman’s glasses absorb less light than the active-shutter systems from Nvidia and Samsung);
- No need for a higher refresh rate (Zalman's passive monitors do not need to work at a refresh rate of 120 Hz; theoretically, they can produce 3D images without refreshing the screen even).
Unfortunately, this technology has its downsides as well.
The first and most conspicuous one is that the monitor’s matrix has a native resolution of 1920x1080 pixels but shows only odd- or even-numbered lines of pixels to each eye in 3D mode. Thus, the effective resolution of the 3D image is only 1920x540 pixels. I must confess, however, that this wasn't a big problem with me unless the game was dull and I had nothing else to do but to scrutinize the textures. In most games I simply forgot about the reduced vertical resolution.
Second, although Zalman claims the ZM-M240W to have the widest viewing angles among all monitors with polarizers (I wonder if any other manufacturer, except Zalman, produces them?), the angles are small for practical purposes. While the horizontal ones are as good as you can expect from a TN matrix and it's quite possible to watch a 3D movie sitting next to your friend, for example, the vertical angles are as small as about 20 degrees in 3D mode. I mean ten degrees up and down from the ideal position. If the angle of viewing is larger, the eyeglasses let the wrong picture pass through, so the left eye gets to see a shadow of the picture intended for the right eye and vice versa. In other words, the 3D image gets totally disrupted.
At my first attempt, choosing a bad angle of viewing, I even thought that the monitor was defective as I could see roughly the same picture with or without the eyeglasses in 3D mode. However, the small viewing angles of the monitor are not as big a problem as they seem. The head of a sitting man stays at about the same level. Changing your posture usually changes your horizontal rather than vertical angle of viewing, and the monitor's horizontal viewing angles are good enough. So, although you should be aware of the small vertical viewing angles of the ZM-M240W in 3D mode, this problem won’t prevent you from enjoying 3D imaging.
Besides, within this range of 10 degrees up and down from the ideal line of viewing, the monitor's 3D image is nearly perfect. The developer has managed to achieve ideal separation between the left and right eyes, so you can see a deep and sharp 3D image without doubling, shadowing or any other undesirable artifacts.
Zalman’s previous product, the 22-inch ZM-M220W that I tested a few years ago, had a problem that showed up in 2D mode but was caused by its 3D functionality. The lines of pixels with different polarization were separated with very fine, yet visible black lines. The ZM-M240W has nothing like that or, at least, the lines have become comparable to the inter-pixel grid in width and are thus invisible.
The monitor’s software is provided by iZ3D. You may know this company by our review of the iZ3D monitor which builds 3D images by using a second LCD matrix and passive polarizer glasses.
Although the Trimon has nothing in common with the iZ3D in terms of technology, that’s not a problem. Realizing that they can hardly compete with first-tier brands by selling their own monitor, people from iZ3D switched to developing and supplying software that can build 3D images using various different technologies and equipment, from dual-color anaglyphic glasses to monitor-based systems.
There is one installation-related problem, by the way. The Zalman Trimon driver is not selected by default, so you will see error messages instead of 3D pictures if you click Next without thinking. Whether you use the distribution from the included disc or download it from the Zalman website, you have to manually select the driver to install. After that, you should choose the Output: Zalman option on the first tab of the installed control panel (see its snapshot above).
The iZ3D software supports graphics cards with both AMD and Nvidia GPUs.
The control panel offers all the settings necessary to manage the 3D mode and the behavior of games. You can find them in the Profiles screen. There are three tabs here. The first one contains general hotkey settings for controlling 3D parameters without leaving the game. You should memorize the hotkeys for convergence, separation and toggling stereo mode as you will need them most often.
The second tab is where you can find general 3D imaging settings for all games. The most important of them are the Stereo separation option which sets the default depth of the scene and the Show wizard checkbox. The latter option will show you step-by-step setup instructions whenever you launch a 3D game. You may find the wizard useful at first and uncheck the checkbox later.
The third tab contains the auto focus setting which is a unique feature of the iZ3D software. It means that 3D parameters are adjusted for the central part of the image (its size is specified in this tab) so that the user could select more 3D depth and get spectacular 3D effects without straining his eyes too much. Enabling this feature affects the performance of the graphics card. Besides, some people don’t like the effect produced by it.
The next menu section contains exceptions. If you want the driver not to react to some game, just add the game in here.
The settings of the control center itself are few. You may also want to look at the Update section. The program can check out for new versions and get updated via the Internet.
I didn't observe systematic errors while running this software although there were a couple of bugs. Sometimes the graphics card's performance would plummet too low (more than the expected 50% performance hit) and at one time the Separation setting worked oddly: I could only switch it between zero (no 3D effect) and a very high level (which made my eyes sore instantly) in a game.
Anyway, I was quite pleased with the overall 3D image quality.
The step-by-step setup wizard that pops up when you launch a 3D game (unless you uncheck the corresponding menu option) was helpful, especially in the first days of my using the Zalman monitor. For example, it helps understand if the 3D mode works at all and what buttons to use to control it (unfortunately, if the 3D mode does not work for some reason, the wizard's diagnostic information boils down to “something must be wrong, so check out everything, perhaps you will fix it with some luck”).
Once the wizard suggested that I set the 3D mode up in Adobe Reader but that was a random bug I couldn't even repeat.
Thus, the iZ3D software with the Zalman Trimon monitor is just as good as the similar drivers from Nvidia and TriDef (the latter is used for the Samsung SA950 monitor). Although not without certain bugs and imperfections, it is quite satisfactory.
Besides, the software bundle provided with the ZM-M240W includes a 3D player which can convert 3D movies recorded in different formats (e.g. side-by-side format when the left- and right-eye frames are encoded side by side) into Zalman’s interlaced format on the fly. The player does this well enough but is inferior to other modern players, such as Media Player Classic – Home Cinema, in the rest of its capabilities and usability. I also noted that it could only work in full-screen mode on the main monitor whereas the ZM-M240W was connected as a secondary one in my system. Anyway, the player copes with its main responsibility, which is to show 3D movies in 3D.
Now that we’ve done with 3D, let’s move on to the monitor's 2D features.