The Nuts and Bolts of Perfect
Image Calibration

Convergence
Optics
Gray Scale (Color Temperature)
Color Decoder/Red Push

Convergence
A precision re-alignment of all parts of the three separate primary color images (Red, Green, and Blue) involved in making a clean, sharp-edged TV picture. On projection systems, customer controls move the entirety of the Red and Blue images horizontally and vertically, to superimpose them properly on the fixed Green image. Behind the scenes, however, are banks of settings that control critical parts of each image until the whole of each picture is symmetrical to the whole of each of the others. Only then can the picture be sharp.

The Test: Aberrations of this alignment usually show up as lines with red & green edges, or blue & yellow edges, rather than crisp black & white edges. These will appear in distinct peripheral areas of the picture, no matter how perfectly the center has been set with the user-controlled crosshairs.

Remember: When a 7" and sometimes 9" diagonal picture is magnified enough to appear as a 50" or 60" or sometimes 73" picture, the least little discrepancy among the 3 superimposed pictures involved is going to show up. It's called "Convergence error."

Aligning these peripheral settings accurately requires achieving delicate balances between and among the three primary color images. This is initially done at the factory, by skilled calibrators, and down the line it is natural for those balances to drift off and away from each other over the years, requiring re-alignment. On a brand new big screen, this also happens "down the road" from the factory – with intercontinental shipping, interstate trucking, warehouse and storage area temperature changes, store demo time, etc. A professional calibrator can re-achieve these balances in short order. An amateur DIYer can cause more harm than good to the picture in a matter of seconds, potentially doubling and even tripling the necessary workload of the calibrator later, after the fact.

Optics
The high voltage inherent in all Cathode Ray Tube (CRT) operation ionizes the air inside the TV, causing all particulates, no matter how small, to be statically charged. As a result they will be inexorably drawn to, and will implant themselves upon, the nearest surface. These surfaces, then, essentially become powerful dust magnets. When the faces of the lenses (front and rear), mirror (possibly two or three), and CRT's – now powerful dust magnets – become matted with pollen, soot, dust, cigarette smoke, and anything and everything else in the air, it shows up in the picture. The result is loss of transparency, crispness, depth and brilliance. The light path must be kept clear, at all points.

The Test: Does the picture appear hazy, fuzzy, and possibly glowing in the dark areas, on dark scenes with bright centerstage? Such build-ups need to be removed at least once every year to retain gleaming, crystalline viewing, with the deeper optics under the lenses – the CRT coolant covers – always being examined at the same time, and attended to if necessary.

These surfaces are very delicate; they can also be made of plastic rather than glass, and they can be internally and externally coated, like camera lenses. All of which serves to suggest that they be cleaned only by a professional, experienced and versed in all of the inherent risks involved, including special considerations about first surface mirrors – which are now standard in HDreadys – and their design and formulation.

There is no second chance once a lens has been scratched, even lightly. No second chance once a mirror has been broken, or even cracked, in the cleaning process.

Remember: After the electronics are properly adjusted and taken care of, a projection TV – whether it's a rear or front projection type – is first and foremost an optical instrument. Like a fine camera or high powered telescope, special treatment must be performed on the optical-grade components involved. This is the path to theater-grade viewing.

"Optics" also includes focus, which is of two types. Electronic, inside the CRT; and mechanical, at the lenses used to project the images onto the screen. With the possible exception of blue electrostatic defocusing, both sets of focusing types must be razor-sharp, on each of the three individual projection systems of the RPTV (Red, Green and Blue).

Electronic focus must also be symmetrical horizontally vs. vertically (astigmatism), and mechanical focus must be symmetrical at center vs. at edges of the screen (Scheimpfluge). Both apply to all CRT based projection sets, be they RPTVs or FPTVs. For fixed pixel displays only the second applies, as Astigmatism only applies to CRT displays.

Gray Scale (Color Temperature)

This is the precision balance of television's primary colors (Red, Green, Blue) without which the countless tones of each combination cannot be accurately achieved. 6500°Kelvin is the industry standard color "temperature" for color televisions, and it must be achieved at all levels of brightness of the picture – from the very brightest to the very darkest parts, and at all points in between, to the extent allowed by the display device involved.

It is a very exacting science, requiring much training and "trial and error" experience before proficiency can be readily called upon in the field, with one's first attempt usually turning into a "baptism of fire". Again, the best results are achieved by a trained and experienced professional; amateur DIYer technique here, as with convergence, can potentially cause more harm than good within minutes, eventually costing the customer much more money in the end than he might have saved by doing it himself.

The Test: Turn all color off by disconnecting the Pb and Pr connections if hooked up via component, or with an accurate grayscale test pattern. Is there a predominant color tinge to the picture, primarily in the dark areas? (greenish, purplish, reddish, etc.?) Is the white really a soft creamy white, or is it driven with blue – and sometimes red – to make it appear “brighter” than other TVs on the showroom floor? On some TV's, whose color level controls never quite turn the colors completely off, it may be necessary to find a black-and-white movie to make the test.

If you're not seeing a pure, uncolored, steely gunmetal gray at all light levels of image, then your color balance is off, and your primary colors need precision realignment using a valid D6500K reference. Or instrumentation, like a color analyzer.

The need for valid D6500K reference cannot be overemphasized, however, because expensive instruments like color analyzers can become uncalibrated themselves and become inaccurate, leading to blind and potentially HIGHLY inaccurate grayscale alignment. A valid D6500K optical reference is the bottomline doublecheck, and should be right there beside every other piece of equipment in a professional calibrator’s arsenal.

Color Decoding
BTW, Grayscale is not color decoding! It is the black and white information, without which the colorations cannot be trusted. Color decoding, which includes things like red push, is also addressed by the Image Perfection protocol.

Red push – an imbalance markedly increasing the red content over the green and blue content at any given color intensity level – has been showing up since before the advent of the HDready RPTV. Mitsubishi is one of the worst offenders. As of this writing, every Mitsubishi HDready series of model since their initial HDready offering has been factory-aligned with red push, OOB. Their explanation is that market survey findings tell them that that is the way their customers prefer it. They are probably right. Even I preferred it that way – it looked “prettier and more colorful” – until I knew the facts. Now that I know the facts – see below – and have experienced actual color decoder accuracy vs. the “prettier and more colorful” picture, I would never go back.

A series of Mit from before the HDreadys contained a selection that had no red push. It was in the user section that contained the choices of “Flesh tone/Average/Accurate” – where Accurate was without the red push that the other 2 selections had. With it set to Accurate, and resetting your color level for accurate fleshtones, you could accomplish linear color decoding simply by choosing that selection.

They are not paying any heed to the videophile market, evidently to Mitsubishi a small and insignificant portion of their market base. Hopefully readers of this particular section will make themselves known to Mitsubishi on their own – to let them know, by phone and/or a well written letter – that videophiles are not just an insignificant portion of their market base. Those of you who, like me, consider it beneath a brand like Mitsubishi, whose HDreadys are far and away some of the best and finest on the market, to be doing this. Otherwise, we videophiles wouldn’t care. We’d just move on. But Mitsubishis are just too fine and gorgeous an HDready to ignore.

Here’s why: When fleshtones are set for accuracy via the user color intensity control in a non-linear, color imbalanced red push situation, red push translates to blue/green diminish – the blues and greens become wilted, washed out and drab. When the color intensity control has been set for accuracy via the blue isolation test – which is industry standard for setting color and tint – the blue appears correctly, but the reds are overaccentuated, and fleshtones appear inappropriately ruddy and sunburned. Very distracting, and highly damaging to our ability to achieve serious suspension of disbelief.

With the color imbalance of red push in the equation you cannot have it both ways. You either have vivid, stunning blues and greens – just like they should be – and ruddy and sunburned looking fleshtones, highly and obviously inaccuate; or you have accurate, lifelike fleshtones and wilted-looking blues and greens. You get either one or the other, and you can’t fudge the fleshtones if you want any kind of accuracy in your picture. For both fleshtones looking correct AND blue and green being vivid to happen simultaneously, either your color decoder needs to be aligned properly with linear tracking response, or you need to take other measures to assure the same thing.

Industry standard is linear tracking among the 3 primary colors, and any display device that is not tracking all 3 colors at the same level is not showing you the image designed for you by the director.

Any display device with INTENTIONAL color push – red push being the worst offender – color pull or any other kind of color imbalance whatsoever, is taking liberties with the industry standard – the color format of encoding and decoding designed for complete accuracy by the video industry for faithful, accurate and effortless reproduction of program material. This is supposed to be unchanged and pristine, sheltering all facets of the original all the way from source: the studio – to the destination: your veiwscreen. Intentional red push on a display device plays fast and loose with the decoding parameters of all color schemes that were encoded accurately at the source.

If you tried to do that with Dolby encoding/decoding in audio, you would never wind up with flat (audiotalk for ideal – pristine, and unchanged from the original) frequency response at your speakers. Faithfully replicating exactly what was recorded when live and in person is the ideal, in audio. Everything in high end audio is designed for faithful replication of the original, and the best systems get their own technology – and potential colorations of the sound – out of the ear of the listener as much as humanly possible, to do so. With anything designed by Mark Levinson, for instance, the performance is simply suspended in 3D in front of you – unencumbered and ethereal, as if you were actually sitting there at the concert itself, in present time, with the instruments bonded to their musicians, each instrument emitting its own distinct and extraordinary sound, with absolutely nothing between you and them but air. No veils, no colorations – what seems to be no hifi equipment! Just the music, suspended in space, magically borne to you in all its native grandeur.

When grayscale and color decoding have been done properly, even commercials show their stuff. Those fruits that go flying through the transparent wall of water in slow motion make your mouth yearn for their juices, and you unconsciously reach for a towel to wipe the splash spray from your face. The richness of their color is mesmerizing; the gleam from the clear-blue water droplets, hypnotic.

"An Image Perfection job is music to the eyes."