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Specifications:
• Display Device: Digital Light
Processing
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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
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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)
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