Nel tentativo (ennesimo) di farvi capire quanto possano valere quei numeri tradotti poi nella realtà, vi riporto un pezzo tratto dalla recensione del plasma LG modello 50PG60 di HomeTheaterMagazine, che sarebbe la sigla americana del nostro 50PG7000, vecchio modello del 2008. Riporto quello perchè ho letto quella recensione proprio ieri notte, mentre stavo cercando altre cose:
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Performance
The first thing I noticed about the LG’s picture was that a blank screen was medium gray. A screen with a full black image—with no input—or a full fade-out between scenes should ideally be (but almost never is) totally black. This is a strong hint that a set has a relatively high black level. The second thing I noticed was that the set’s picture was remarkably impressive despite this.
I’ll get to the inevitable discussion of black level and shadow detail before you can finish that cheeseburger and fries. But first let’s look at the things that the LG does extremely well. And there are plenty. Its post- calibration color is superb. More than a year after its release, Pirates of the Caribbean: The Curse of the Black Pearl remains one of the best Blu-ray transfers on the market. The bright opening scenes, from Jack Sparrow’s star-making entrance to his initial escape, were striking. Fleshtones were natural, the green foliage of Port Royal was convincingly real, the sky was a perfect shade of blue, and the red of the British uniforms was a solid crimson.
The second Pirates film on Blu-ray, Pirates of the Caribbean: Dead Man’s Chest, is a significantly different-looking disc. It’s a bit more subdued and moody, touched with a trace of sepia, and a little grainier. But it’s no less impressive, and the LG clearly brought out the visual differences between these two transfers.
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Hidalgo is also loaded with fine detail. The film’s many harshly lit desert scenes showed the set’s ability to clearly render details of backlit, shadowed faces without obscuring them or lightening them too much. This isn’t an easy balance to get right. The few dark scenes in this film do have well-lit highlights, which helped them from turning as gray as the set’s performance on a full black screen suggested they would.
My early reaction to the set’s black-level performance was that it was superior (on most of the program material I checked) to the Mitsubishi LT-52149 LCD I also review in this issue (page 82). The star field near the beginning of Stargate: Continuum and the scenes of the tramp steamer on the ocean at night from the same film both appeared to have more punch on the LG. However, neither scene was exactly a knockout on either set. The same was the case with dark scenes from Master and Commander: The Far Side of the World.
However, as it turned out, the LG’s measured black level was unimpressive and nowhere near as good as the measured black level on the Mitsubishi. Nevertheless, on a side- by-side comparison, the LG was clearly the superior set. The two sets didn’t look all that different on many dark scenes despite the measurements. When they did differ, the LG clearly looked better. That was also true of the set’s crispness of detail and the accuracy and naturalness of its color. The LG’s image was clearly less bright than the LCD set on very bright images. Still, I can only explain this discrepancy between the measurements and my subjective viewing impressions by pointing to the fact that the LG’s image popped off the screen with a more convincingly real vividness on mid- and low-brightness scenes. This isn’t the first time I’ve noticed this phenomenon on a plasma set."
Non ho sottolineato le varie frasi salienti, perchè quanto sopra merita letto con
attenzione e
interamente 
.
A parte quanto sopra, che già basterebbe, ricordo che:
1. La maggior parte degli strumenti di tipo amatoriale/semi professionale, che sono poi quelli che spesso usano molti recensori, non è spesso in grado di restituire una misurazione esatta del livello "estremo" del nero, per limiti della stessa strumentazione.
2. Se lo strumento stesso non è stato periodicamente ricalibrato, ancora peggio di quanto al punto 1.
3. Quando si prendono in esame i numeri rilevati da una misurazione, e si fanno comparazioni con modelli diversi di TV, anche di altre marche, l'unica comparazione che si potrebbe considerare corretta (per quel che può valere, visto quanto sopra) è solo se le misurazioni eseguite nelle diverse recensioni prese in esame sono state eseguite dallo stesso tecnico, e con la stessa strumentazione.
Infine, last but not least, se non calibrate correttamente il vostro TV, usando il controllo "Luminosità" in primis, e avendo settato correttamente qualche altro parametro che riguarda il livello del nero, se presente, i numeri che avete letto in giro per il Web ve li potete scordare completamente. Questo vuol anche dire che un TV di marca xxx semi sconosciuta o "diffamata", calibrato correttamente può dare una resa sui neri migliore di un altro che costa il 50% in più, ma che è stato calibrato male.
E concludo facendo notare che le normali condizioni di utilizzo, nelle nostre abitazioni, sono molto diverse da quelle utilizzate in un laboratorio, dove una misurazione del livello del nero, noto tutto quanto riportato sopra, diventa nella pratica più una curiosità tecnica che un numero atto a stabilire la "supremazia" di un plasma rispetto ad un altro.
saludos
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