Samsung HL-S xx87/88 DLP Consumer Report Part I
Over the last several years, DLP displays have emerged as a major contender to Plasma, LCoS, LCD, and CRT, offering benefits that neither of the aforementioned technologies can offer. Devised by Texas Instruments back in the 80's, DLP technology is now implemented by a growing number of manufacturers. But it is a manufacturer's unique design that differentiates their DLP display from the competition (connectivity, video processing, software, interface, cabinet style, etc.). The sum total of these design characteristics will ultimately determine how well the display will perform.
At Avical, we decided that a thorough lab testing of several of these models were needed to determine their strengths and weaknesses. Our goals were to 1) quantify their performance 2) find out how the manufacturer was implementing the technology and 3) determine the best way to optimize these displays for our clients. In this report, we will focus on the Samsung HL-S5687W 56" DLP display.
What makes a good display?
Very simply put, a display that can abide by system standards would be considered a good display. But what are "system standards?" These are recommended guidelines outlined by members of the film and television industry (SMPTE) to be used for accurate visual communication of different video systems. Contrary to what many believe, a good picture is much more scientific than subjective.
Throughout the production process, key individuals such as the director, cinematographer, and colorist, will work diligently trying to determine the best film stock to use, lighting, and the color/hue for a particular scene and/or program. Likewise, if a display meets the standards used during the production of said material, it will afford the opportunity to accurately see what these individuals worked so hard to create. But if it doesn't, it will impose its own idiosyncratic characteristics upon the material thus skewing the way it is exhibited and therefore experienced.
In evaluating the HL-S5687W, we focused on how well it conformed to NTSC and ATSC system standards pre and post calibration.
Initial Testing
The first phase of testing centered on the out-of-the-box (OTB) settings without making any adjustments to the display in order to determine how close to the standard it came from the factory. For test patterns, an Accupel HDG-3000 and a custom computer test pattern generation system were employed at native 1080i and 1080p respectively via component and HDMI. Measurements were taken utilizing a Photo Research PR650 spectroradiometer and a Minolta LS100 light meter. Lastly, the room in which the measurements were taken had total control over ambient lighting.
OTB, the set was far from ideal. The black level was too high causing blacks to be washed out. Contrast was also too high resulting in clipping and possible eye-fatigue for some. Color decoding was inaccurate as well. The gamma was set in the service menu to approximately 1.95 but became relatively flat below 25%.
Furthermore, the DNIe circuitry was turned ON which caused black level to float. In other words, a dark scene would cause the circuit to raise black level, while a bright scene would cause the black level to be reduced. This type of circuitry allows for the manufacturer to achieve a higher on/off contrast ratio but at the expense of truncating image detail during normal viewing.
There was also a significant amount of edge enhancement in the picture both vertically and horizontally. A good portion of this can be attributed to the DNIe circuitry - which can be an article in and of itself.
Lastly, the colorimetry out of the box was far from the SMPTE C or HD standard. The color difference diagram (see below) shows the disparity between the measured color coordinates and the SMPTE standards. It may be difficult to put this into perspective so we have also plotted these on the 1931 CIE chromaticity chart chart to further illustrate the differences.
Color Error Chart – SMPTE C
- The bottom left of the triangle represents blue, the top left green, and the right side red. Notice how the display does not include certain shades of blue as specified for SMPTE C.
Color Error Chart – SMPTE HD
The bottom left of the triangle represents blue, the top left is green, and the right side red. Notice how the display does not include certain shades of blue as specified for SMPTE HD.
Looking at the above comparisons, the display did not appear to accurately reproduce SMPTE C or SMPTE HD color space OTB. However, if the native color coordinates could be manipulated enough to allow for a larger color gamut, than perhaps we could align them to SMPTE standards thus correcting the errors shown above. We ended up turning off the color coordinate adjustment software so that we could more closely inspect the color wheel independent of any correction done by the display. This in turn allowed us to determine the maximum color gamut that the display was capable of.
Color Gamut Chart – Native vs. HD
The chart above illustrates that the display’s native color gamut is not capable of fully reproducing all of the colors in the SMPTE HD system. While this was disappointing, it is important to note that the vast majority of displays on the market do not meet this specification. We hope that Samsung and other companies will encourage Texas Instruments to rectify this issue in future designs.
Grayscale Tracking
Grayscale tracking was far from ideal also and exhibited a decidedly bluish cast as shown by our measurements below.
To summarize, the Samsung line of HL-S DLP displays have many areas that need improving before they can present material accurately. But in reality, this can be said for just about any display. The real question remains just how well they can be made to adhere to system standards.
Service-menu adjustability
These displays have an extensive service menu that can prove to be daunting to all but the most experienced video calibrationist. We began by turning off all of the picture parameters that were detrimental to image quality (most notably those associated with DNIe). We then adjusted brightness and contrast. This in turn allowed us to more closely inspect gamma for which there were several settings to choose from within the service menu. To ensure that we were using the most accurate one for our application, we measure them all.
The factory gamma was already measured to be 1.95. This is included below to allow for an easy comparison of the different gamma look-up tables (LUTs).
Gamma 1.95 (OTB factory setting)
- The red line represents a power function with the value of 1.95, whereas the blue line represents gamma as measured from the factory. Below 25%, the gamma became relatively flat.
Gamma 1.95
- Notice how the gamma curve is still 1.95, but matches the standard power function of 1.95 instead of going relative flat at 25% as seen in the factory setting.
Gamma 1.95
Gamma 2.5
- This gamma came the closest to the gamma range specified by the system. We measured this near black and found that the curve went to 1.7. We hope Samsung will correct this in the future.
Gamma .95
Gamma 1.5
Gamma 1.9
Gamma 2.14
For our purpose of trying to align the display within the 2.2-2.8 SMPTE standard, we opted for a gamma setting of 2.5.
To conclude Part I of this report, the OTB factory settings have been determined to deviate from system standards. In preparation for the calibration, floating black was eliminated and excessive edge enhancement reduced. Brightness and contrast were properly set and the most accurate gamma setting had been determined.
Part II of this article will delve into the adjustable capabilities concerning colorimetry.
