Fixed Pixel Displays (general description)
The definition “fixed pixel displays” covers quite a number of different types of technologies. Some of these technologies include DLP, LCD, and PLASMA. There are substantial differences between these kinds of displays but what they all have in common is that they do indeed have a fixed number of pixels. These displays are also digital by design and are capable of rendering a sharper and crisper image then the traditional look of a CRT based display.
In spite of there differences, most fixed pixel displays require a similar procedure in terms of what they need when they are calibrated. Also, I am proud to be one of only a hand full of calibrators at present who is installing a neutral density filter in these units when I calibrate them. This procedure will dramatically improve the image quality on just about any fixed pixel display.
Along with this new technology, there also seems to be new roomers and misunderstandings amongst consumers. Most notably, there is a notion that fixed pixel displays will not benefit from a calibration. Nothing could be further from the truth though. The fact is that I often encounter fixed pixel displays that actually measure worse out of the box then any CRT based display I have seen.
First and foremost, I inspect the TV for any defects that may affect the quality of the calibration. If I find any problems I will point them out. Assuming there is nothing wrong with the display I will then quickly get started.
Any projection fixed pixel display, new or old, needs its optics cleaned. This of course includes any lenses or mirrors in the set. Also, on many DLP type displays the color wheel can be removed and cleaned.
One may assume that an older used display will need cleaning. Also, it seems natural that one may think that their new TV came from the factory with clean optics. However, this is never the case. Unfortunately manufacturers don’t seem concerned about the cleanliness of the optics, even when you take your new set right out of the box. It is very common for even brand new displays to have a large accumulation of dust on the lenses, mirrors, and the color wheel. I have also seen many cases where rear projectors have large spider webs in the cabinet passing right across the screen.
Cleaning the optics will improve the image in many ways. Most notably the sharpness and detail will be better. Also, the color, brightness, and the general realism of the picture will get better.
Geometry calibration requirements vary greatly from display model to display model. Also, the introduction of the new DLP displays using three chips has made this area much more complicated.
The new three chip DLP’s require nearly the same amount of work and correction that a CRT might need. Geometry on these sets can take several hours or more. On the other hand, many fixed pixel displays do not have very stringent geometry requirements. Some only allow for minor electrical geometry positioning combined with a few mechanical corrections. Geometry on these sets usually takes just an hour or less.
The geometry requirements of your particular display will influence the price of the calibration. Fixed pixel calibrations requiring only minor geometry adjustments generally are priced cheaper then displays require more intense correction.
Neutral Density Filter Installation
Installing a neutral density filter over the lenses of a fixed pixel display will improve the black level and black details. A neutral density filter will also aid in establishing a gamma curve that more closely matches industry standard. A better gamma curve will make the picture richer and more life like without making it look over saturated or unrealistic.
I am proud to be one of only a hand full of calibrators who is well versed in this procedure. I have also aided in the research and development in this area and I am always contributing new knowledge to this technique. In fact, you will be hard pressed to locate anyone else who is capable of performing this modification.
Almost all fixed pixel displays will likely benefit from a neutral density filter. However, the type and strength of filter will vary from display to display and the requirements are not constant. I come equipped with a collection of filters and will find one that suits your display perfectly. The installation of a neutral density filter is a custom job. Also, it should be noted that this mod will not affect your warrantee status either.
A neutral density filter is a filter that blocks light while allowing some light to pass through. The strength of the filter dictates the amount of light that is allowed to pass. The paramount characteristic of a neutral density filter is that any light it allows to pass will have the same color. In other words, the filter passes light without tainting it and can be considered neutral.
The results on the picture are as follows. The image will take on a much richer and fuller appearance. The picture will look much more realistic and three dimensional. Color and skin tones will look more natural and richer but colors will not appear oversaturated at all. Also, the black level will be far better and blacks will become blacker. In fact, after installing a neutral density filter on a fixed pixel display, the blacks and black details will have quality much closer to what is expected from a CRT.
The most important thing to note when installing a neutral density filter is that brightness, contrast, gamma, and grey scale will need to be redone from scratch. This is why I install the neutral density filter before I make any of these adjustments.
Color Decoder Alignment to SMTPE Standards
This is one of the most important steps in a calibration. Not only will I address the well documented red-push exhibited by most displays, but I also fix the lesser known problems of misalignment of blue, green, magenta, cyan, and yellow. I will fix the color decoder and make it conform as closely as possible to industry standards. I will use my Accupel pattern generator along with my Sencore color analyzer to help guide my adjustments. Color decoder alignment will have a dramatic impact on the final image quality.
Brightness and Contrast
Something so easy as brightness and contrast can often be overlooked. Perhaps this is because it’s actually not so easy to make these adjustments correctly. It really is difficult to tell just how dark or bright a picture is by eye, even when looking at test patterns.
I use my Accupel calibration generator along with my Sencore light meter so set and maintain both proper brightness and contrast. This is paramount for what will come next in establishing a nice gamma curve and allowing grey to track linearly. Also, for some types of fixed pixel displays setting proper contrast will extend the life of the set and lessen the likelihood of burn-in.
Sharpness and Edge Enhancements
To set sharpness I will rely heavily on my Accupel’s test patterns. I’ll find the sharpness setting that is technically correct for your display. I will then use a multitude of test patterns to detect and identify any edge enhancements that can be adjusted. Reducing or completely eliminating edge enhancements will make the image look more realistic and film like. Proper sharpness setting and reduction of edge enhancements go a long way in giving a display the 3-D effect. These adjustments will help in giving the sensation that you could reach right into the screen and touch the image.
Gamma is one of the least understood and most important adjustments to be made in a calibration. Honestly, I think adjusting gamma goes right over the heads of a lot of calibrators as I know of many who simply don’t worry about it. Setting gamma correctly can however have a most profound impact on the image. Without proper gamma adjustment black details will be lost and the image will either appear too washed out or way to dark. No matter how accurately brightness and contrast are set; if gamma is in error the picture will still have fundamental problems.
Gamma calibration is not so straight forward so I customize gamma based on your viewing habits. I use my Sencore to take light readings and make adjustments throughout the entire light emission spectrum. Industry standards dictate that gamma should be maintained between 2.2 and 2.5. If you tend to watch in a darker room then you will prefer gamma closer to 2.5. Inversely, if you have a room with bright lighting or large windows then you will likely prefer gamma closer to 2.2.
Some displays are not very cooperative when it comes to establishing a nice gamma curve. Many current fixed pixel displays will exhibit a low gamma curve that will wash out the picture slightly. On these displays I may not be able to attain a gamma curve that quite matches industry standard. In these rare cases I will get the gamma as close as the display will allow. In any event, you can be certain that my calibrated gamma curve will be far better then the settings the display had right out of the box.
Calibrate Grey Scale to D65
Gamma, brightness, contrast, and other settings will change and interfere with grey tracking. Therefore I try and leave grey scale calibration for the final adjustment. Only after all of the above procedures are completed will I then calibrate grey scale. For television, I set grey scale to the industry standard of 6500 degrees Kelvin. This is a difficult task and usually takes about two hours or slightly less. If your display requires a standard other then D65 I am capable of providing this as well.
When most people hear about setting grey scale they don’t normally really understand what it does. I think people assume that grey scale is not very important or may only affect objects on the screen that are grey or black or white. However this is definitely not the whole story. The most profound impact proper grey scale calibration will have on the image is to dramatically improve the richness and realism of colors. This is because colors in a color display are only imposed on top of black and white images.
Typically manufacturers will set grey scale to accentuate a color in order to make their display stand out on the show room flour. This is apparent because black and white images look colored. However, when color video is watched this extra color in the grey scale will be apparent in the image by skewing the color and exaggerating it. Once grey is calibrated all images will become more natural and have fuller color but at the same time the image will not look over saturated. Grey scale calibration is one of the most import procedures in any video display calibration.
Time and Pricing
A fixed pixel display will typically require between four to twelve hours of labor to calibrate. The amount of time required is directly related to the model of the display and its subsequent geometry capabilities. As such, pricing is based on the amount of time required and will generally fall between $495 and $645 for a full calibration. As stated, price is based on the complexity of the geometry adjustments required. It is however safe to say that most fixed pixel displays will fall towards the low end of the pricing scale as most current models do not have these extensive geometry adjustments. Please send me an email or fill out my appointment form for an exact quote on your model.