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Product Review
 

Optoma H55 Single-Chip 4:3 DLP Digital Multimedia Projector

January, 2003

Steve Smallcombe

 

 

Specifications:


• Display Device: Digital Light Processing

• DLP™ Technology by Texas Instruments
• Brightness: 1000 ANSI Lumens
• Aspect Ratio(s): 4:3 Native,

      5:4 / 16:9 Compatible
• Contrast Ratio: 1000:1
• Lamp: 200 W User Replaceable UHP Lamp
• Lamp Life: 2000 hours
• Lens: 1:1.2 Manual Zoom and Manual Focus;

      F / 2.44 - 2.69, f = 28.8 - 34.5 mm
• Keystone: Correction: + / -16 Degrees
• Input: Computer: DVI Connector; S-Video,

      Composite , HDB 15-Pin D-Sub

      (Component Video / HDTV input port)
• Audible Noise: 32
• Weight: 6.4 lbs.
• Dimensions: 10.9" (W) x 8.9" (D) x 3.3" (H)
      277 x 225 x 85 mm

MSRP $7,995 USA

(4,599 at ProjectorPeople.com)

http://www.optoma.com

 

Introduction

The Optoma H55 is a very small lightweight projector – just the sort of projector I would like to take on a business trip. In fact, I did use the H55 for several business related PowerPoint presentations and, for that purpose, it is ideal as the H55 comes with a very nice carrying case. Optoma has also given the H55 a set of features that make suitable it for use in a Home Theater (HT) environment. Although the H55 is a native 4x3, XGA (1024x768) projector, it does have all the modes necessary to properly project DVD of all aspect ratios as well as High Definition (”HD”) television when used with an appropriate set-top box.

The H55 is based on the Digital Light Processing (DLP) or Digital Micromirror Device (DMD) technology developed by Texas Instruments. DLP technology uses an array of very tiny mirrors on a chip. The mirrors rotate or flip about 10° in response to the input video signal, thus reflecting the light from the bulb through the lens onto the screen, or off to one side. For a given pixel, the light is either switched on or off – a 1 or a 0 – hence the word “Digital” in DLP and DMD.

DLP technology offers several potential advantages over Liquid Crystal Displays (LCD), and these has made DLP-based projectors very popular in recent years for both business and HT usage. In particular DLP projectors have a much better pixel “fill factor,” that is more of the area of an individual pixel is used for the picture as opposed to the grid (boundary) surrounding the pixel. With all digital or fixed panel projectors (non CRT), the grid between the individual pixels is static, wasted space, and can be a source of what is know as Fixed Pattern Noise (FPN). FPN is most commonly referred to as the “screen door effect”, and many viewers find FPN to be objectionable when it is noticeable. Because of it higher fill factor, DLP based projectors generally produce a much smoother looking image with less FPN compared to LCD-based projectors of similar resolution.

The H55 is a 4x3 XGA projector, with a 1024x768 pixel resolution. At this point, let me state my bias relative to projectors meant for HT usage. I believe, given the ready availability of widescreen DVDs that preserve the movie’s original aspect ratio and the advent of HDTV, that home theaters today should be set up using a 16x9 screen, and for fixed panels projectors, projectors with 16x9 native panels. Resolution is really the issue. When a 16x9 image is shown on a 4x3 XGA projector, such as the H55, the active picture area occupies 1024x576 pixels. In comparison, projectors that use the WXGA format of 1366x768, such as my reference projector (a Sony 11HT) have 1.8 times the number of pixels in the active picture area for widescreen, or 16x9, images. More pixels in the image allow better definition or resolution, especially with HD where the source content is as good or better than all fixed panel projectors in HT use today. More pixels generally also leads to a smoother image, although in this case the better fill factor of the DLP format more than likely makes up for some loss of resolution.

The second advantage often identified with DLP-based projectors is a high contrast ratio and efficient use of light. Contrast ratio is figure of merit that compares the ratio between the brightest white and the darkest black that a projector can produce. The light output of the projector in Lumens and the contrast ratio are are generally considered two of the most important performance indicators for HT usage. Generally, a better contrast ratios leads to better black levels and, therefore, a more realistic presentation of darker scenes in movies, etc. The H55's specifications are 1000:1 for contrast ratio, with a light output of 1000 ANSI Lumens.

While DLP technology has several significant advantages over competing technologies such as LCD, it also has several potential drawbacks, especially in a single chip design like the H55, based on the way color and shades of gray are produced. As mentioned above, when the mirrors flip they can turn light on or off (1 or 0). Video images consist of many different shades of gray or luminosity and, more often than not, also have color. To make the many shades of gray, or regions of varying light intensity, the mirrors have to flip on and off rapidly so that the eye (or the brain) averages or integrates the image and perceives the desired light level. Other forms of averaging or dithering may also be applied to regions of the screen to further extend the number of levels of gray that can be perceived by the viewer.

In “single-chip” DLP-based projectors like the H55, the or perception of color is created in a similar way to how the levels of gray are made. To make colored images, light from the bulb passes through a “Color Wheel,” a small rapidly rotating wheel with red, green and blue windows or colored filters, before it hits the DLP chip. (Color wheels on some single-chip DLP base projectors also have a clear or white section.) To make red, the light from the chip is turned on when the red window in the wheel is aligned with the light path, etc. Sequentially turning on the red and blue for a given pixel makes purple, etc. Thus by rapidly flipping the mirrors in synchronization with the color wheel, the projector can make all the colors and shades of gray needed for video images. While it is hard to imagine many tiny mirrors flipping so quickly to make a moving image, the system obviously works and DLP-based projectors are among the most popular and well thought of models available today. For a very informative explanation of how DLP works visit http://www.dlp.com and take the demo.

The potential drawback of this single-chip DLP technology is that in any given instant, the picture on the screen is not the desired image, but is instead rapidly alternating between images consisting of the individual red, green and blue colors. Thus the eye and the brain play the last critical role in making single chip DLP projectors work, by combining or averaging or integrating the picture, so that the viewer perceives the desired image and not the rapidly flashing momentary components of the image.

With a static picture from a single-chip DLP-based projector, it is easy to understand how this averaging works well. Where things potentially start to fail is when there is motion in the image, or when one blinks or rapidly moves one’s eyes quickly between various parts of the image. In these cases, the perceptual integration of the image may break down and one might see “rainbows” or false flashes of color, in the image. Shown below is a representation of what this looks like. It occurs when you move your eyes, because the red, green, and blue parts of the image are flashed on the screen in a sequence, and as your eyes move, you see the sequence of color.

Some individuals have also reported getting headaches after watching single-chip DLP projectors for any length of time. It appears that not all individuals handle this color averaging process equally well. Newer single-chip DLP-based projectors, such as the H55, use a higher speed color wheel, thus greatly reducing the likelihood that an individual will perceive these artifacts.

In contrast, three-chip projectors use a separate chip for the red, green, and blue colors and, thus, simultaneously present the RGB images so that no temporal averaging or integration by the user is necessary. Today virtually all LCD based projectors intended for HT usage are 3-chip projectors. Three-chip DLP projectors also exist, but these are very expensive and are typically for commercial use only.

Thus in today’s HT projector market one can select DLP-based projectors with their better contrast ratios, better black levels and smoother image, but with the risk that some individuals may see artifacts that are not present with competing designs. Obviously this is very much an individual decision, and I was anxious to see how the H55 compared in practice to LCD-based projectors, such as my reference projector, the SONY 11HT or the recently reviewed PLV-70 and TW100, all or which are LCD-based designs.

Inputs and Connectivity

The H55 can easily connect with any input you are likely to give it, although at first you might ask, “Where are the component inputs?” The 15-Pin D-Sub connector seen above can be used for both Component Video and HDTV signals with the provided adaptor cable as well as for VGA-based inputs. (The H55 came with a very complete set of cables.) There are also S-Video and Composite Video ports, along with a DVI port for connection to a computer or other DVI-compatible devices. Virtually every input mode has it own (mono) audio input via an Audio Mini Jack.

Controls

The remote control contains all of the controls to select inputs and aspect ratios, as well as tweak the projector via the on-screen menu system. As is the custom, most of these buttons are also duplicated on the top of the projector. There are also several other buttons on the remote that are quite handy such as the ‘16x9/4x3’ button that changes the aspect ratio of the projector to handle anamorphic (enhanced for 16x9) or 4x3 images. The ‘Color Temp” button toggles between the ‘Low,’ ’Mid’ and ‘High’ color temperatures. The HDTV button selects the HDTV input mode, handy as the H55 does not automatically recognize and switch to the HDTV mode. Focus is adjustable through the typical arrangement of a rotating ring on the lens assembly. A zoom ring is located on the top of the projector. The H55 also has a digital image ‘Zoom’ button that allows the user to temporarily zoom in on part of the image. This should not be confused with the optical zoom feature that ones uses to adjust the image to fit the screen.

User-Level Adjustments

The Optoma H55 offers a very simple menu system with navigation by convenient tabs as shown below.

The Image 1 tab allows the user to adjust ‘Brightness’ and ‘Contrast’, as well as ‘Color”, ‘Tint’ and ‘Sharpness’ using a test disk such as Avia. The ‘Color Temp’ and ‘Keystone’ adjustment are also available via the Image II tab.

Setting ‘Brightness’ accurately is essential as it assures a consistent definition for black between the source and the projector. If the ‘Brightness’ is set too high, then the black level is not as good as the projector is capable of producing. If ‘Brightness’ is set too low, then parts of the image that are intended to be shadows or details in dark scenes are lost. Setting the ‘Brightness’ accurately can be done either by using the Avia ‘black bars’, or using light meter sensitive to low light levels, and a black screen.

Setting the ‘Contrast’ is exactly the same thing, but for white. Set it too low and you will lose image brightness and contrast ratio. Set it too high and you will lose details in the highlights of the picture.

'Color Temp' allows the user to select a color temperature in several steps labeled ‘Low’, ‘Mid’ and ‘High’. My initial setting was the 3rd click from the left or essentially just below the ‘Mid’ position.

Placement in the Room

Since the H55 is a 4x3 projector and I have a 16x9 screen, I had several choices as how to proceed. Since I wanted to compare the image at a size similar to that used with my reference projector, I decided to place the projector so that 16x9 images would fill my 16x9 screen. With my 102 inch diagonal Da-Lite Da-matte (gain=1) screen, this meant placing the projector 16 feet from the screen. This was actually quite a convenient location in my room, right behind the couch, and essentially the same position as I have used for projectors with a “long throw lens” like the Sanyo PLV-70.

For watching 4x3 material, I moved the projector forward to a coffee table in front of the couch. With a 4x3 screen, as fixed setup would be more realistic as, one would simply leave the projector at the distance necessary to fill the 4x3 screen. The central portion of the screen would then be used for 16x9 images. This means, of course, that the 16x9 or widescreen images will be smaller than the 4x3 images (not my preference) but if your current viewing habits involve largely 4x3 images and only the occasional widescreen image, then a 4x3 projector and screen may well be your best choice.

The H55 projects an image with the bottom of the image higher than the lens, and this allows for convenient placement on a table that is lower than the bottom of the screen without the need for keystone correction. In my case, however, the back of my couch was above the bottom of the screen, so I ended up with the projector higher than optimal and angled down so as to position the middle 16x9 portion of the 4x3 image in my 16x9 screen. For whatever reason, I could not get the keystone correction to work for 16x9 images with the component input. When using a 4x3 projector to fill a 16x9 screen there was light-spill from the unused portions of the 4x3 DLP panels above and below the screen.

The Fan noise on the H55 is specified at 32 dB, but as the noise and hot air exited the front of the projector where, in my case, the seating area was located. Thus, I found the H55 to be a bit noisier than other projectors I have used. On the other hand, there should be no problem placing the H55 right up against a back wall.

Measurements and Viewing

When I evaluate a projector, I not only look at images, I measure the color balance of the projector at various light intensity levels and determine the quality of what is called ‘grayscale tracking’. The idea is that black, white, and all shades of gray, should have the correct ratio of the three primary colors used in video projection, Red, Green and Blue.

Projector meant for HT usage, typically make white by shining just the right proportion of red green and blue light on the screen. Ideally shades of gray should have the same proportion of red, green and blue as white, but less of each color. What’s important is that this RGB ratio be the ‘correct’ ratio, and that this ratio remains constant as the intensity of the light in the image changes. This ability for the color balance to track properly with the different levels of light intensity is therefore what is called ‘grayscale tracking’.

Why is this so important? Well, imagine watching a black and white movie on your color projector. Ideally whites should look white, blacks should look black and all the shades of gray should look, well gray. If the projector in the darker part of the image, used too much green, the shadows would seem a bit greenish, and that would be distracting. If the highlights looked yellow, that would also be distracting. So, it is important that all light intensity levels of ‘gray’ have the same ratio of all three colors to achieve a good black and white image on a color projector. Grayscale tracking is also important with color images, as one does not want the color of an object to change as the level of illumination changes, or is in a shadow. Good grayscale tracking, however, requires careful calibration – typically beyond that done by the manufacturer or easily done by a user without test equipment.

When testing projectors, I use a system I developed called “SMART”, which measures the intensity of the three primary colors using test images and shows the results in several types of graphs. In particular, SMART uses the Avia disc to display a series of images in which windows appear in the center of the screen, against a black background, that represent black and white and various shades of gray in linear steps of 10 IRE units. (IRE is term use to represent the video input voltage level with black represented by IRE 0, and white by IRE 100.) With each of these IRE windows, SMART uses a highly sensitive light meter (SMART III) and colored filters to measure the light intensity of each of the primary colors at each IRE level. To learn more about SMART, visit http://www.smartavtweaks.com.

The Light Intensity data from the H55 as a function the video input signal, or IRE level, are shown in the chart above. In this case, the ‘Color Temp’ setting in the menu was 3rd click from the left or just below the ‘Mid’ position. Using Avia, I determined that the proper ‘Brightness’ setting was 48, and that the proper ‘Contrast’ setting was 68. 'Color' and 'Tint' were correct at the default values.

What we see in the above graph above are traces for red, green and blue, which all rise along pretty much the same curve, but with the red curve just a bit below the others. This indicates that the initial setting I chose was very close to the desired color temperature of 6,500K. The measured light level at the 16x9 screen with an IRE 100 window was 12.7 ft-L. This corresponds to 666 Lumens out of the projector assuming a 4x3 image. If, however, one is using the projector with a 16x9 screen, as I was, then the effective Lumens rating drops to 374 (as light from about half the pixels are not used). The measured contrast ratio (IRE 100 window vs. black) was 396:1.

As discussed above, a consistent ratio of colors as a function of IRE level is perhaps equally important to overall picture quality as having an absolutely correct color temperature. In the color intensity chart above, it is difficult to the details of the color balance at the low IRE level, or how the overall color intensity compares to the ideal for that IRE level. For these purposes, SMART uses two different charts one for color balance and one for gamma tracking.

In the color balance chart generated by SMART, we can compare the ratios of the various colors at the various IRE levels. In this case, the intensity for the individual colors is compared to the average intensity for that IRE level.

In the color balance chart, ideally all three curves would stay very close to 1 at all IRE levels indicating that the color balance was the desired one, and did not change as a function of IRE level.

As can be seen in the above Color Balance graph, the H55 out of the box, shows consistent color balance at the higher IRE levels, but is deficient in red at the lowest IRE levels. The deviation towards the blue-green at the low IRE level means that the shadow or darker areas of the image will have a blue-green tint, and this can detract from the picture quality. As an example, with the un-tweaked H55, the IRE 20 window on Avia looked quite green compared to the blacker background.

This chart also shows that the color temperature is a bit high (red is too low) using the initial setting, but again very close to the desire color temperature.

(Often in reviews, one will see plots of Color Temperature vs. IRE level as a way of showing the quality of a projector's grayscale tracking. Color temperature tells you about the ratio of blue to red in the image. SMART uses a similar display to show the behavior of all three colors.)

Gamma Tracking

The other thing we need to look at in more detail is gamma tracking, or how the light output of the projector responds to the input signal. As mentioned above, the relationship between input signal level and light output is not linear, as one might expect, but follows an exponential function. The exponent of this function is referred to as gamma for the display. If the projector tracks the desired function properly, then the image will appear as the director intended with shadow details preserved at low IRE levels and highlight detail maintained at the high IRE levels. If the projector's gamma tracking is off, then details in the image will either be lost or the image may look flat and have little contrast.

Gamma tracking can be graphed for red green and blue separately, or as shown below, for the overall light intensity where the color intensities of red, green and blue are combined in a manner similar to how the human eye sees light intensity.

In particular, the gamma tracking graph shows the ratio of the measured combined light level to a theoretical level calculated, in this case, using a target gamma value of 2.4. If the projector is accurately producing the intended light intensity level as a function of IRE level, then the gamma tracking graph will show ratios at all IRE levels that are close to 1. If the projector is putting out less light than the ideal, then the gamma tracking chart will proportionally show a value of less than 1.

In the Gamma Tracking graph we can see that the H55, with the initial settings, shows quite good gamma tracking with just a bit too much light at the lower IRE levels than the ideal. This is not a problem and will simply mean that the shadow details are perhaps just a bit lighter than intended.

Tweaking the Optima H55

One of the real advantages of accurately characterizing a projector's performance is that you can then use the same measurement system as a guide to tweaking or improving the projected image. Tweaking typically involves changing various control parameters in the projector, such as those that allow adjustment of drive or gain levels and offsets or bias settings for the primary colors. These controls are located in the service mode on most projectors as adjusting such parameters typically require accurate measurements and experience. Fortunately, Optoma provided me with the key to enter the service mode and I was quickly able to find the necessary gain and bias parameters for each of the primary colors.

I found that the bias settings could be used to correct the color balance at IRE 10 and 20, but had a fairly minimal effect at IRE 0. Fortunately, these adjustments fairly dramatically improved the perceived color of these “gray” IRE 10 and 20 windows. Raising the red bias also put the overall temperature balance right on target as can be seen above. I did not have to change the gains at all to achieve the proper color balance. While the color balance of IRE 0 is still a bit green, the color balance from IRE 20 upward is very consistent and right at the desired D65. The contrast ratio after tweaking dropped slightly to 375:1. Gamma tracking and total light output did not change significantly.

Color Decoder Accuracy

At this point it is very important to understand the difference between grayscale tracking accuracy and color decoder accuracy. As discussed above, grayscale tracking has to do with the proportion of red, green and blue in black and white and all the shades of gray. If all we watched were black and white (and gray) movies, this would be sufficient. With color images we also care how accurately colors are made. Red is red, of course, but we want to have reds of various levels of saturation or ‘redness’, and we want combinations of the primary colors to make all the other colors in all their various levels of saturation. Making accurate colors is the job of the color decoder. When someone says that a projector has ‘red push’ they mean that red is more saturated in the image than was intended, not that there is too much red in the white and gray parts of the image. These are separate issues and should not be confused.

When we use the blue filter and a color bar test image to set up the color control using a test disc, we are controlling the level of saturation of blue. The Avia disc has another very useful test image called the Color Decoder test in the Special Tests menu that tests the level of saturation for all three primary colors. Hence, the Avia disc comes with a green and red filter to use in this test, as well as the more common blue one. In the Color Decoder test the appropriate filter is to check the color decoder accuracy for that primary color. The image contains a gray background and a series of red, green and blue colored squares of differing levels of saturation. If you had previously set the color control accurately using the color bar test and now use the blue filter to look at the Color Decoder image, you should see that the blue square labeled 0% is about the same level of intensity as the gray background. This would indicate that the color decoder is set up accurately for blue. With an accurate color decoder one would get a match at 0% for the other two colors as well, using the other two filters and looking at the red and green squares. If, on the other hand, the red square labeled 20% matched the gray background, then you could conclude that that the projector had 20% red “push”.

With the H55, the ‘Color’, using the color menu at the default setting, I could not detect any color decoder errors. This means that the H55 should produce very accurate colors.

Scaler and Deinterlacer

The H55 has 1024x768 pixels on its DLP chip, and this pixel grid determines the resolution of the display. Virtually all video input sources, however, have a different resolution than that of the display, and it is the job of a scaler to convert, either via expansion or compression, the input signal to the appropriate resolution ("native resolution") for the display panels. Furthermore, many current sources for video are interlaced, and a deinterlacer is needed to intelligently combine the appropriate fields of the interlaced signal to make complete frames for the inherently progressive LCD display. Combine all this with the need to support different display modes, aspect ratios for 4x3, 16x9 and letterboxed images, and you have quite a complex problem.

Not too many years ago, one could have paid far more than the cost of this projector for a scaler and deinterlacer to perform just these tasks. Fortunately, today, most of the projectors aimed at the HT market have scalers and deinterlacers built in, and the H55 is no exception.

While in future reviews I plan to perform more specific tests on deinterlacers included with projectors (and DVD players), with the H55 I simply watched familiar DVDs using the progressive output from my Denon 1600 DVD player (480p) and HDTV signals from my DISH 6000 (1080i) via the component inputs. I did not see any noticeable artifacts that could be attributed to the scaler in the H55. Standard Definition digital broadcasts from the DISH 6000 also looked as expected via the S-Video input.

If you have a DVD player with a progressive output option, it is worth checking the image on the H55 using both the progressive and interlaced modes, to see which deinterlacer – the one in the DVD player or the one in the projector – gives the best looking image.

The H55 is a 4x3 projector, but it does support “unsqueezing” anamorphic DVDs, thus allowing the best possible resolution from DVD sources. As mentioned above, however, use of this projector, or other 4x3 projectors is a bit inconvenient with 16x9 screens. The 4x3 mode is used to support both “normal” 4x3 material and “letterboxed” non-anomorphic images.

Video Memories

With the H55 I did not find any evidence video memories where the user can store aspect ratios, contrast and brightness settings, etc. At first this seemed to be a major shortcoming of the H55 for HT usage. I was pleased, however, to discover that the projector did remember the previous contrast and brightness setting, etc., when switching inputs or sources, such as when switching from HDTV to DVDs. This is very handy as, with my setup at least, these two sources required significantly different settings for contrast and brightness, and I was concerned that I would constantly need to be adjusting these values as I changed sources. I find that automatically remembering the previous setting for a given input format is the most convenient way of managing the need for multiple settings with multiple sources, and the H55 handled this quite well. (Both component DVD signals and component HDTV signals use the same input, but are different input formats.)

Viewing and Comments

As I mentioned earlier, my first experience with the H55 was in a business setting. I needed a projector for a PowerPoint presentation (I do have a “day job”) and, since I had a variety of projectors at home at that point, it seemed easier to bring one from home, than borrowing one from the IT group. Plus, it gave me a chance to get acquainted with the “new toy.” The Optoma H55 was the obvious choice for this task as it was the smallest and lightest projector of the bunch, and it came packaged in its own carrying case with all the necessary cables, etc. Setup was quick and easy and the projected image looked bright and had very accurate color, better than the Toshiba I normally use in my “day job.” The most remarkable difference, however, was the smoothness of the image. The better fill factor of the DLP chip, compared to the LCD projectors with which I was more familiar, was very apparent, and in a very positive way. It actually made it a bit harder to focus as I could no longer use the pixel grid for focusing. Not a bad problem at all!

Based on this very positive experience, I was anxious to view the H55 in my HT. I set it up for 16x9 images as described above. I began by watching a bit of Lord of the Rings, Fellowship of the Rings, (“LOTR”) which for all practical purposes has become my reference DVD, and the DISH Demo loop in HTDV. I also watched many parts of Galaxy Quest and The Fifth Element, two other favorite DVDs. Overall, the color balance seemed right on, and as expected, the image was very smooth. The black levels with the H55, however, were not quite what I expected based on other DLP projectors I have seen. The blacks and shadows were definitely a bit “greenish”. Measurements using SMART confirmed the green cast at the lowest IRE levels. Fortunately, this problem was largely fixed using the service mode adjustments as described above.

The contrast ratio I measured with the H55 was similar to, but a bit less than my reference projector. I have used SMART to measure other DLP-based projectors and typically they came out much closer to 1000:1 than the 375-400:1 I measured with the H55. I also recently measured a newer model DLP-based projector with the “HD2” chip and was very pleased to see a contrast ratio of 1770:1. These other DLP-based systems did not, however, produce nearly as much light as the H55 or come nearly as close as the H55 in achieving their Lumens specification. The H55, as a 4x3 projector at least, is capable of making a much brighter image than many of its DLP-based competitors. When used to produce a 16x9 image, however, 44 percent of the H55s pixels are unused and the Lumens rating suffers accordingly.

At a 400:1 contrast ratio, all scenes except the low contrast darker scenes will look great. The darker scenes will look a bit washed out, and even at twice this contrast ratio that would still be true. Getting the colors of the lower IRE levels into balance with the rest of the picture did lead to significant improvement in overall picture quality and made watching the darker scenes much more enjoyable and realistic.

Despite these quibbles, I’ll have to admit that, once calibrated, the H55 made a very nice 16x9 image. The overall brightness and contrast ratio were close to my SMART/CC filter tweaked 11HT. The colors, however, seemed a bit less saturated than with my reference projector. The lack of screen door effect or FPN was particularly welcome with the H55, as I consider FPN to be one of the major reasons that I may someday replace my 11HT. Even though the H55 was using only about half the pixels of my reference projector, the image was clearly smoother. DLP wins this one – no question.

With DVDs or standard definition TV the resolution of the H55 in the 16x9 mode was more than adequate for the task and, again, the lack of FPN made for a very nice smooth image. With HDTV, however, the limited number of pixels in the image started to detract from the apparent resolution, and I’ll have to give the nod to my reference projector for HDTV viewing. The HD images on the H55 looked fine, just not quite as sharp as I was used to.

Rainbows? No, I didn’t really see any rainbows from my normal viewing position, watching normal video images. In order to see rainbows with the H55, I selected a movie with rolling credits, white letters moving on a black background, the best (worst) possible situation if you want to see rainbows. I then walked up very close to the screen and by moving my eyes quickly or by looking at the letters when they first rolled onto the screen, there were the rainbows. Seeing rainbows was interesting from a scientific point of view, but certainly not a problem for me with normal viewing conditions. Individual sensitivities do vary so check this out for yourself if you are considering buying a single-chip DLP-based system.

In setting up the H55, I did observe one other artifact and, for some, this may more significant than rainbows. When I was using the moving black bars in the Avia ‘Black Bars’ test to set the brightness, it was obvious that the moving bars were not a uniform dark gray color. The moving bars consisted of lighter and darker flashing speckles – a result, no doubt, of the dithering or averaging that is used define the intermediate levels of dark gray. I could definitely see this artifact from my normal seating position (3.3 times the screen height). It was even clearer if I walked closer to the screen. I saw these same artifacts in other dark scenes and it detracted from their realism. Properly adjusted, black, or the projectors rendition of black, should not show these artifacts, as the projector does not need dithering to make black – the pixels in that region are simply off. Light levels right above black however, i.e shadow details, are where this problem shows up, as the projector apparently approximates these darker gray areas by dithering black and lighter gray pixels. This kind of dithering artifact may not be a problem for all users, so check it out before you buy.

Conclusions

The Optoma H55, a single-chip DLP-based projector, is capable of producing a bright, smooth image, smoother than LCD-based designs, and brighter than many of its other DLP-based competitors. The H55 is a 4x3 projector, and while I prefer to use a 16x9 projector in my own HT, if you feel that most of your viewing will be of 4x3 material then the H55 and a 4x3 screen would be a very good choice. The H55 has also been equipped with all the tools necessary to make properly displayed 16x9 images although it uses only about half of its pixels in the process. There are certain artifacts associated with single-chip DLP-based system that you should be aware of, and you should find out how sensitive you and others who are likely to watch your system are to these artifacts. For many people the very smooth image associated with the DLP-based design of the H55 will more than compensate for these other potential issues.


- Steve Smallcombe -

Reference Equipment:

Denon 1600 DVD player B&K Ref 30 preamplifier
Theta Dreadnaught 5x225 amplifier
Acurus 200x3 amplifier (two channels used for rear speakers)
Adcom Power Center
KimberCable interconnects and speaker wire
DISH 6000 HDTV receiver
Velodyne DF-661 front speakers (modified crossover) - 3
Definitive Technology surround speakers - 4
Velodyne 15" subwoofers - 2
SONY VLP-VW11HT video projector (reference projector, tweaked with CC40R filter)

Related to the article above, we recommend the following:

Primer - TVs
   

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