Οι παλαιότεροι θα θυμουνται πως το θέμα Xenon vs UHP lamps μας ειχε απασχολήσει παλαιότερα εδω .
Ειχα ομως μεγάλη απορία για το πως βλέπουν το ζήτημα στην άλλη πλευρά του Ατλαντικού, γι'αυτό ανοιξα ενα σχετικό θέμα στο avsforum, οπου τους ρωτούσα το εξής ερώτημα:
Εστω οτι εχουμε στην διάθεση μας δύο προβολείς παραπλήσιους τεχνολογικά οπως ο Sony VW-200 (με Xenon lamp) και ο Sony VW-60 ή ο JVC HD-100 (με UHP lamp) και μπορούν να ρυθμιστούν με ακριβή όργανα και μέσω ενος εξωτερικού Video Processor με δυνατότητες CMS (οπως ο Lumagen RadianceXD), έτσι ώστε και οι δύο προβολείς δινουν ακριβώς ιδια χρωματομετρικά αποτελέσματα βασει των standards (πχ Rec 709), το ερωτημα ειναι: Θα ειναι το χρωμα τους το ιδιο ενωπιον των ματιών μας;
Αν και περιμενα μεγαλή αντιπαραθεση απόψεων, προς έκπληξη μου διαπίστωσα οτι η πλειοψηφια των εμπειρων χρηστων και επαγγελματιων τείνει προς την αποψη πως εφόσον δύο προβολείς, ανεξαρτήτως λάμπας και τεχνολογίας, δίνουν ακριβώς τα ίδια αποτελεσματα στις μετρήσεις, τότε το χρώμα τους θα πρέπει να είναι το ίδιο στα ματια μας.
Καποιοι θεωρούν οτι η χρήση λαμπών Xenon στους οικιακούς προβολείς γινεται για λογους Marketing αφου ολες οι λαμπες των προβολέων μας (Xenon ή UHP) φιλτράρονται υποχρεωτικά προκειμένου να δωσουν την σωστή θερμοκρασία λευκού (D65). Αντιθέτως στον κινηματογράφο χρησιμοποιουνται αποκλειστικά οι λαμπες xenon διοτι στο φιλμ οι σωστή θερμοκρασία λευκού ειναι D55 η οποια συμπίπτει με την θερμοκρασια λευκου της λαμπας Xenon, ενω φυσικά λογω τεχνολογίας των μηχανών προβολης δεν νοειται το φιλτράρισμα της λάμπας για διορθωση της θερμοκρασιας λευκου που εκπεμπει.
Μερικές απο τις πιο ενδιαφερουσες τοποθετήσεις:
Ποια ειναι η αποψη σας επι του θέματος;
Ειχα ομως μεγάλη απορία για το πως βλέπουν το ζήτημα στην άλλη πλευρά του Ατλαντικού, γι'αυτό ανοιξα ενα σχετικό θέμα στο avsforum, οπου τους ρωτούσα το εξής ερώτημα:
Εστω οτι εχουμε στην διάθεση μας δύο προβολείς παραπλήσιους τεχνολογικά οπως ο Sony VW-200 (με Xenon lamp) και ο Sony VW-60 ή ο JVC HD-100 (με UHP lamp) και μπορούν να ρυθμιστούν με ακριβή όργανα και μέσω ενος εξωτερικού Video Processor με δυνατότητες CMS (οπως ο Lumagen RadianceXD), έτσι ώστε και οι δύο προβολείς δινουν ακριβώς ιδια χρωματομετρικά αποτελέσματα βασει των standards (πχ Rec 709), το ερωτημα ειναι: Θα ειναι το χρωμα τους το ιδιο ενωπιον των ματιών μας;
Αν και περιμενα μεγαλή αντιπαραθεση απόψεων, προς έκπληξη μου διαπίστωσα οτι η πλειοψηφια των εμπειρων χρηστων και επαγγελματιων τείνει προς την αποψη πως εφόσον δύο προβολείς, ανεξαρτήτως λάμπας και τεχνολογίας, δίνουν ακριβώς τα ίδια αποτελεσματα στις μετρήσεις, τότε το χρώμα τους θα πρέπει να είναι το ίδιο στα ματια μας.
Καποιοι θεωρούν οτι η χρήση λαμπών Xenon στους οικιακούς προβολείς γινεται για λογους Marketing αφου ολες οι λαμπες των προβολέων μας (Xenon ή UHP) φιλτράρονται υποχρεωτικά προκειμένου να δωσουν την σωστή θερμοκρασία λευκού (D65). Αντιθέτως στον κινηματογράφο χρησιμοποιουνται αποκλειστικά οι λαμπες xenon διοτι στο φιλμ οι σωστή θερμοκρασία λευκού ειναι D55 η οποια συμπίπτει με την θερμοκρασια λευκου της λαμπας Xenon, ενω φυσικά λογω τεχνολογίας των μηχανών προβολης δεν νοειται το φιλτράρισμα της λάμπας για διορθωση της θερμοκρασιας λευκου που εκπεμπει.
Μερικές απο τις πιο ενδιαφερουσες τοποθετήσεις:
I see it this way:
A Xenon lamp natively provides a more balanced light. UHP lamps are less balanced. Thus, calibrating a Xenon based projector to 6500k would require less loss of light than calibrating a similarly situated UHP-based projector.
Once calibrated, it should make no difference. Calibrated is calibrated.
But, there are many reports that UHP lamps lose, for instance, red, at a faster rate than other colors. This may requre further calibration and perhaps more loss of lumens. I have not heard many reports about how Xenon lamps age in this regard.
But, it has been reported that Xenon lamps lose lumens very rapidly as they age, moreso than UHP lamps. I have seen many dim Rubys that can attest to that fact.
Xenon lamps are usually more expensive, and have to be replaced more frequently, than UHP lamps. Thus, whatever theoretical advantage a Xenon lamp might have is lost after a few hundred hours.
Neither UHP nor Xenon yield ideal D65 without color filtering. UHP is actually closer though which is why it's a more efficient technology (more filtered lumens per watt). For D-cinema applications where brightness is everything. Xenon is the preferred technology simply because of the availability of high wattage bulbs. This in turn has driven D-Cinema to deviate from D65 in order to achieve even higher lumens. The D-Cinema spec uses a color temperature closer to Xenon's natural spectrum (something like 5500K but I may be mistaken).
As far as which technology yields the better colors goes, this has been hashed and rehashed on this forum over the years (check the archives) and pretty much every expert in this field has come out and said that it makes no difference. I think that Sony's use of Xenon on the higher-end projectors has been the result of a great marketing campaign.
"Ahh.. a "taboo" issue."
Not taboo, just strong opinions and eternal debate on whether it matters or not.
"We need as flat a spectrum as we can get from 360 to 730 nanometers (along with a lot of luminous output)"
For pj I thought we want it as spiky as possible (think laser), it's having the three RGB spikes where they belong.
wm, DILA color calibrator extraordinaire, who I haven't seen around here for awhile, dismissed the idea of xenon's superiority and said good color depends on filtering and calibration.
Most Xenon is native 55k not 65k.
Xenon is todays choice for film projection. With film there are no filters in the light path to correct for the use of other lamp technologies. Film is also timed for the spectra of Xenon.
Not sure how Xenon verse UHP filtered effect our electronic displays but I bet manufactures can show supportive benefits to both.
To 'answer' the OP question---if the primaries and secondaries and white point are identical---you will see no difference. I have yet to meet someone who sees spectra and not colours. There is one reason though higher end units with lots of lumen use xenon. It has nothing to do with colorimetry and everything with the fact that xenon lamps are more or less freely scalable. Try to buy a 4kw or a 12kw UHP lamp, there is none and there will likely never be one.
Like I had mentioned before..Greg rogers said it like it is.
2 plus 3 = 5
1 plus 4 = 5
Same results but with different ways of getting there.
I can not count to high so I had to keep things simple.
Well, yes. The type of bulb is a design choice, one choice in a system with many parts. And yes, both types of bulbs appear to be capable of generating identical post-calibration results. And if all we're interested in is whether or not there are any differences in colorimetry, then we can be satisfied that there need not be. And if a person was concerned about brightness loss due to excessive green filtering on UHP, then I guess he'd just need to look at some reviews for post-calibration lumens to make sure he'd be satisfied.
But I'd still be interested to know whether or not there would be any practical differences in the overall functioning of the projector due to the selection of one bulb type versus another. For example, do Xenon bulbs tend to lose fewer lumens post-calibration? Does the picture on UHP bulbs tend to take on a green cast if the contrast is jacked up too high (generally yes), but perhaps some other result occurs when using Xenon? Any other differences?
Listen, I'm not really arguing, and I'm certainly not pretending to know the answers. I'm just saying that just because both types of bulbs are capable of being filtered to produce identical results does not necessarily mean that the choice of bulb has no practical impact on the operation of the projector.
There is a long thread around here somewhere on this very topic that got pretty heated as I recall. I'm surprised everyone seems to agree on this issue now. I guess we've come a long way.
UHP provides more D65 filtered lumens per watt.
Yes, the spectrum of UHP is not as "even" as that of Xenon. Thus, while you may have to filter out 35% more blue on a UHP system, if UHP is 85% more efficient, you are still ahead of the game on a total lumen yield vs. power consumed basis. This is why the 250W UHP Pearl is just about the same brightness as the 400W Xenon Ruby.
Would the two technologies look identical if filtered to produce identical RGB spectral intensities and calibrated identically? YES..
Do manufacturers cheat a little and sacrifice some color fidelity in order to pump out a few more lumens, or perhaps oversaturate colors to please consumers? YES (which explains why the Pearl and Ruby don't necessarily have identical color reproduction).
So it is... if the primaries, secondaries and whitepoint are the same and if the brightness of the projectors is matched they should look virtually identical with respect to colour... With the Sony and JVC you have to keep in mind though that the dynamic iris may affect the situtation in some low APL scenes, as the JVC which doesn't use a DI will create brighter hightlights in these scenes than the Sony, and that may affect you colour-perception (you could then identify the UHP projector due to it's apparently higher on/off). You would need measurement equipment to tell which uses Xenon and which UHP...
To say anything other than yes would suggest that there is some unidentified variable that affects the visible color which isn't addressed in our current calibration measurements and procedures. I don't have any way of knowing whether that is a possibility or not, but can speculate on a few factors that might potentially make a difference but aren't currently measured or are practical to calibrate (AFAIK).
- What if the different light sources radiate energy differently outside the normal visible spectrum and this affects the sensitivity of our eyes within the visible spectrum? If that were true, then projectors that were calibrated to measure the same would still visibly look different.
- Our calibration methods seem to focus on getting the coordinates of the primaries and secondaries correct, but as far as I know don't address the linearity of relative saturation within the CIE triangle. Nonlinearities of this type could make things look different while still having the calibrated points measure the same.
- Since we're talking practical, I don't know whether one type of lamp versus the other consistently maintains their relative spectral power density the same as the bulb ages. At the moment of calibration they might look the same, but might quickly diverge over time (between calibrations.)
I guess this comes down to how you feel about our current understanding of the vision system and calibration techniques. If you think that we've already identified and measure every factor which contributes to color vision, then yes - projectors which are calibrated to be the same will look the same, like a mathematical identity.
If you believe that there are possible factors that we don't understand yet which contribute to the mix in visual color perception, then A might not always equal A.
In my experience LCOS makes the whole debate mute (it does not matter) while 3dlp exaxerbates it (I can see it a mile away ,like comparing an incandecent bulb to LED, the later is extremely clinical and inorganic).
Ποια ειναι η αποψη σας επι του θέματος;