CurtPalme.com Home Theater Forum

[VideoGrabber]

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[This is a sincere question, asked with good intentions and meant to bash no one. I'm not a digital-guy, and have no idea what the answer is, though it may well be common knowledge to those that are. If we could avoid comparisons to analog technologies, that would be great.]

I've gotten the impression (perhaps incorrectly) that the UHP/UHM lamps used in most digital PJs tend to initially drop off fairly quickly in brightness from their new state. Something along the lines of ~50% in the first ~500 hours or so, then tapering more slowly during the remainder of their 2,000-3,000(?) hour expected life-spans?

I was wondering how people feel about/deal with this luminosity profile? Do you, e.g. start in a Low or Econo mode, then step up to High/Normal after the drop-off occurs? Or use iris/aperture modifications, or a neutral-density lens? Or some other method, or combination? One thing I've noted on one unit (PT-AE4000) is that varying the aperture (zoom level) by later sliding the PJ just a couple feet closer, can increase on-screen ftL by as much as 50%, which may be an effective compensating technique, if your install enables it.

This aspect of digital-ownership seems like a big hassle to me, but perhaps it's really not? Also, does anyone use their digital PJ long enough to ever actually need a new bulb, before upgrading to a new PJ? If so, did the new bulb get acquired because the old one popped, or because the brightness dropped uncomfortably low? What were your experiences?

Or am I completely FOS, and the reality is nothing like this? I'd appreciate the education. Thanks!

[ecrabb]

Tim,

I'm not a digital owner, but from everything I've read your characterization is spot-on: You do lose about half of the brightness in roughly the first 500 hours. Now, consider a couple of things.

First, for a lot of people, that's a year (maybe two) of movies. At that point, you can sell the bulb with only 500 hours on it and buy another. A $300 bulb once every couple of years isn't a big deal for most people, especially if you can sell the used one for $100-150.

Of course, you can also just use the projector as-is and still have a very nice image, as long as you aren't pushing the envelope on screen size or throw distance to begin with. As you mentioned, if you're at the end of the zoom lens, the lens is less efficient. You can plan for the dropoff when you're installing if you don't want to replace bulbs as often.

For instance, take a JVC RS20 at 900 ANSI lumens. Let's say after calibration, it's running closer to 700 lumens. Throw that on a 96x54 1.3 gain screen and you get about 25ftL, so a year later if you've dropped to half that, you're probably still in the 12ftL+ ballpark - just fine for most. But, if you were running a 120x67 screen and had 16ftL to work with when the bulb was new, you might be at 8ftL at the 500-hour mark. Most of us would want to replace the bulb at that point. That's probably too big of a screen/too low of a gain for that projector.

I think most guys just let the brightness drop off, and replace the bulb whenever they start to find it objectionable. You can always whip out a meter and check it if you suspect it isn't to your liking.

SC

[WanMan]

I fully expect that the initial light output of a lamp to change over time. Unfortunately, I think a lot of factors can go into the actual lamp behavior over its individual life cycle. I say this, because I read posts by folks with the exact same projector and lamp producing two completely different stories even though their setups might be spot on.

And then there are external consideration, too. For instance, I have been reading about some JVC units whereby the lamp surface takes on a coating that can be cleaned off, and also the first glass on the projector (that the lamp faces). When cleaned, varying amounts of some substance is removed and varying amounts of lumens are recovered. Worse yet is that this condition, while specific to JVC, isn't specific to one model or another.

Now add to this the variation of operating environment, varying operating settings (low/normal/high lamp outputs), and the differences in manufacturing, it has gotten to be a very difficult process to track and find a common denominator. All I can say is I'll be measuring on 100-hour intervals, cleaning on another interval (depending on what the first cleaning finds), and providing it for the masses.

But, I have already concluded that unlike the flat-panels in my home I'll be using this projector exclusively for BD. So, the rate in which hours accumulates will be slower than normal. The replacement lamp can be had (OEM part) for $300. If I only go 500 hours then my annual lamp cost is $300. But I expect to be looking at an upgrade in another couple of years, and this unit getting sold or re-purposed.

[VideoGrabber]

Thanks, guys.

> At that point, you can sell the bulb with only 500 hours on it and buy another. A $300 bulb once every couple of years isn't a big deal for most people, especially if you can sell the used one for $100-150. <

That's a possibility I hadn't thought about, Steve. Flip that around, and if you initially designed for the lower lumens past 500 hrs (assuming the falloff after that is a slow deterioration), you could buy 500-hr bulbs used from others (who required the initial higher output) and get the remaining 1500+ hours for $100 (while they paid $200 for the first 500). Rate1 = 40c/hr, rate2 = 7c/hr.

I guess I'd be more concerned about dealing with variations in luminosity, than the actual levels (though someone with a huge screen wouldn't have the luxury of options). I think the key point is perhaps your comment...

> First, for a lot of people, that's a year (maybe two) of movies. <

If that's the case, then it's a fairly minor issue, not requiring much (if any) pre-planning. I.e., the answer is that perhaps most people don't deal with the two significantly different brightness levels.

I have little free time for movie-watching myself these days, but I'm hopeful to be at the point some day where I'd effectively be burning through two 500-hr bulbs/year. I guess even new that would be fairly 'cheap' if one was spending that much time focused on that activity (<70c/movie, assuming some resale value, as you suggested). And even changing a bulb every 6 months wouldn't be too onerous. Thanks for the perspective.

Wan, I'll be interested in hearing about your 100-hour checkpoint measurements.

[ecrabb]

[garyfritz]

I also suspect that getting a digital professionally calibrated is a waste of money -- because not only do the bulbs change in brightness, I believe they also shift color a bit. So you cough up $800-1000 to have a pro tweak the colors, and within a few hundred hours they're significantly off. Better to get a sensor and learn how to do it yourself so you can tweak it as often as you want.

Hopefully LED projectors will resolve these issues... though I've heard they have some dropoff / color shift too?

[WanMan]

Gary, where did you hear this about LED's? You say you hear, but then place a question mark. So, you are questioning whether or not you have heard this?

[VideoGrabber]

> Hopefully LED projectors will resolve these issues... though I've heard they have some dropoff / color shift too? <

I can't speak to projectors (well, front projectors), but my TV with PhlatLight LED sources (a Samsung 61" (53x30") 1080p DLP-based RPTV) shows no sign of either issue after only 3,000 hours. Not too surprising, since Samsung claims they're good up to 60,000 hours, and the manufacturer claims 100k hours. I do believe they drop to 50% output after about 50k hours or so, but there's so much extra capacity there that in my case means I could bump the output and have the set brighter at EndOfLife than when I first started using it.

OTOH, for front projection you'd need lots more lumens, and that could accelerate the process quite a bit. Only 11 sq-ft for my RP, vs. 2-4 times that for FP. In general though, equivalent LED sources will have ~10x the lifespan of the bulbs. And less than half the power draw. I'm guessing we're 3-5 years away from LED-based FP-units being price/performance competitive with bulbs. But the fact that there's no need to change bulbs or do frequent/periodic re-cals (unless the 3 LEDs age at different rates, which is possible) will make them worth considering before that point is reached.

(One other advantage being that the light output is continuously variable, vs. having just 2 points, as with bulbs. And that DI type functions can be implemented electronically (on a per-color basis, even), in micro-seconds, with no latencies due to inertia from mechanical assemblies.)

[VideoGrabber]

SC,

thanks for the thread pointer and the graph. In that case it looks more like a 30% dropoff, rather than 50. And a fair bit of disagreement whether those results are typical or not. Informative reading, none-the-less.

> Once you see a nice, big, bright, digital picture, it is hard to get used to not having it. <

I guess I'll have to take your word for that (I know Dave would agree), but I'm not so sure that's true for everyone. I'm used to something in the neighborhood of 12-ftL in a completely dark room. I don't recall exactly, but when I cal'ed my living-room TV 18 months ago, it was around 24 ftL or so. That's a 53"-wide screen in a shaded but illuminated room. (I know some go 50-ftL or more on TVs, but that's not me.) Make the room pitch-black, and that's too bright (for me). I was thinking something around 16 ftL for a digital PJ would be about right, but I have no need for or interest in a tanning machine in the HT.

[garyfritz]

[WanMan]

I think the whole premise behind the industry trying to move into LED is because of this seemingly unchanging condition in LED light source.

[garyfritz]

I think there are a whole bunch of reasons, and unchanging light source *may* be one of them:

* Lower cost
* Lower power consumption
* Simpler manufacturing (no/smaller fan, no color wheel, etc)
* More reliable (though I'm not convinced they actually care about this)
* Customers want a solution that doesn't require $300+ bulbs

etc

[AaronB]

Let's not forget that Phospor dims as it ages too! That's why you can see burned-in areas of your tubes. Well-used Phospor produces less light than the less-used areas of the tube, which remain bright. You need to replace tubes just like you replace a digital's bulb, and usually for the same reason... dimming output as a result of usage (and maybe the occasional implosion). In fact, both follow a similar exponential decay over time (quick at first and tapering off). Here's a big difference: most bulbs are $200 to $400, but a set of 3 9" CRT's... well. Might as well replace the PJ when/if it comes to that. Another big difference is that the bulb will need replacing maybe 5 to 10 times over the lifespan of a single set of tubes. Both UHP lamps and CRTs will experience color shift over time. The 3 CRTs will not likely age at the same rate, and the color of each will also shift a little over time. Same with the UHP bulb, the color spectrum shifts with usage. So if you are really anal about color, you will want to calibrate every 100 to 200 hours with a digital and maybe half as often with a CRT (and less often as tubes age unless you really burn one).

[Curt Palme]

AAronB, I disagree with about 1/2 what you posted.

Fact is, digital projectors on average are designed to last 2-3 bulb lifes before the chassis self destructs due to heat. You won't find many digitals that are still working after 4 bulbs. So you need to factor the cost of a new projector in with bulb costs on a digital.


I disagree that CRT light output dies exponentially. I've never measured it, but I'd think it was a pretty linear drop as compared to hours used. Can anyone back me on that?

You can legitimately get 10,000 hours out of a set of CRT tubes, as long as you're a bit conservative with brightness and contrast. More hours out of a 9" set.

Yes you'll get color shift on a CRT, but calibration every 400 hours? Nah, try 1000-1500, even for the most anal of people.

[Curt Palme]

AAronB, I disagree with about 1/2 what you posted.

Fact is, digital projectors on average are designed to last 2-3 bulb lifes before the chassis self destructs due to heat. You won't find many digitals that are still working after 4 bulbs. So you need to factor the cost of a new projector in with bulb costs on a digital.


I disagree that CRT light output dies exponentially. I've never measured it, but I'd think it was a pretty linear drop as compared to hours used. Can anyone back me on that?

You can legitimately get 10,000 hours out of a set of CRT tubes, as long as you're a bit conservative with brightness and contrast. More hours out of a 9" set.

Yes you'll get color shift on a CRT, but calibration every 400 hours? Nah, try 1000-1500, even for the most anal of people.

[WanMan]

I'm not sure I would say the metal-halides (aka Phosphors) dim with aging, but rather wear according to setup and preference--as Curt pointed out. And while the wearing of the metal-halide is there, it is no different than same output drops and resulting coloring shifting of lamps. Each technology and product have their own quirks.

[AaronB]

[garyfritz]

From what I've read, a UHP bulb loses half its brightness within a few hundred hours. That's hardly a "used up" bulb.

This post showed a 50% drop in less than 500 hours.

This image (from that same thread but another user) shows a bit less dropoff than that, but still a lot. He posted later numbers saying he was at 300 lumens at 890 hours, which would tend to indicate a *linear* dropoff, not logarithmic. At less than 1000 he had half his original brightness. Optoma claimed the H79 should get 3000 hours in economy mode (which is what he ran until 750 hours) and 2000 in bright mode.

[WanMan]

Well, there is a difference to me in one's decision-making process. If someone wanted a nice bright projector (and not just [pseudo] pixel resolution) the costs of a ownership long-term is quite different. A set of G90 tubes would run the equivalent of ten lamps for my JVC RS20. While some would say the G90 would last a lot longer in lifecycle, I might tend to agree. But, I would also recognize the average life-cycle is only as good, and appropriate, if that is what someone is looking for.

Imagine those that like to lease cars for a couple of year. I could argue I could spend $3K on the RS20 with the intentions of getting half back. At the same time, I only expect to run 2-3 lamps through it. Why would I do this? Why wouldn't I would be the better question. I would always be looking to replace something with something better. And while this cannot be said for everything out there, it can surely be said about digital projectors.

And while Curt is a good buy and all, I cannot see myself trying to maintain, year in and out, than the digital. Now, if money were no object then I'd have several 9" CRT projectors, but considering trying to get a hold of one when I was looking to buy and when I bought something else, the costs were prohibitive. Heck, just paying for someone to come in and setup and calibrate would have cost me the equivalent of four to five lamps.

BTW, if you are easily seeing a 16x9 pattern after 1,000 hours then you are already over-driving the unit. Those electron guns are sending enough electrons to tear apart the metal-halide molecules. Damage is already done.

[garyfritz]

[WanMan]

Yeah, I am sure there are folks showing signs of that, but also there are folks with +3000 hours on their given model projectors not showing signs. Warranties on projectors are not based on the number of hours. For instance, if I put 5,000 hours on the RS20 then by insinuation it will burn out well before the warranty, right? But I have the warranty.