CurtPalme.com Home Theater Forum

Panayotis Melas · Joined: 24 May 2008 Posts: 13 Location: Kallithea, Greece

Can somebody give me an accurate, simple and brief description of the definitions "Peak Lumens" and "ANSI Lumens" and their differences?

For example, when I read that a NEC XG135LC has a brightness of 1100 Peak Lumens, how this number can be expressed in ANSI Lumens?

Thanks

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

ecrabb · Posted: Tue Nov 18, 2008 7:11 pm Post subject:

ANSI lumens are measured using an ANSI-standard method for adjusting the projector so that you can distinguish between 90, 95, and 100% white, then displaying a full-white field and measuring brightness.

Peak lumens are measured with a small window in the center of the screen - usually 10 or 20 percent of the image area.

So, there isn't a way to "express" peak lumens as ANSI lumens or vice-versa because they're different - at least with a CRT. A CRT projector, because of the nature of the device, can display a much brighter white in a small are than it can in a larger area. OTOH, a digital projector will display the same amount of white regardless of how much white is displayed.

A typical 8" CRT like an XG or G70 might measure 1100 peak lumens (in a 20% window), will probably only measure only 200 lumens displaying a full-white field (ANSI lumens).

On low-APL content like a space scene or a night scene, CRT looks awesome. On high-APL content like a snowy scene on a sunny day (Happy Feet, Ice Age, Fargo, etc.), that's where CRT falls short. Whites aren't bright white, but are instead a dingy or grayish white.

SC

ecrabb · Posted: Tue Nov 18, 2008 7:16 pm Post subject:

Baaah! You beat me, Dave!!!

I always wondered... Why couldn't the projector manufacturers just build bigger HVPS's so current draw wouldn't have to be quite so severely limited? I'm sure there were some design limitations (size, cost, heat?), but why couldn't they have gotten to a 3:1 or even 4:1 relationship (window:full-field) instead of 6:1 Or, is it the tubes themselves that can't be driven that hard?

SC

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

ecrabb · Posted: Tue Nov 18, 2008 9:33 pm Post subject:

Dave, oops - miscommunication on my part. I didn't mean to imply that CRT looked great with low-APL material because of the low light output.

Instead of saying "CRT looks awesome with a space or night scene" and leaving it, I should have said that the good peak light output COMBINED with low black levels makes those scenes look great. For instance, it's the night or space scenes where CRT's really shine. The CRT's peak output can make those stars damn bright, while displaying them against the CRT's inky black background. That's the very definition of high contrast.

Of course, things start getting iffy for the CRT in higher-APL scenes where ANSI contrast gets pretty poor. Then, things go south further with very high-APL scenes where you have both poor ANSI contrast AND low ANSI light output. A smallish black car in a brightly-lit snowy scene is a worst-case scenario for CRT. You'll have both elevated black levels on the car and dingy whites on the snow.

OTOH, a digital shines in the black car/bright snowy scene (or Ice Age, Happy Feet, etc.) and sucks a little on the space and night scenes.

Sorry for the confusion.

SC

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

tony359 · Joined: 04 Aug 2006 Posts: 378

Can someone give me some impression on brightness between Sony 1271 and NEC XG135LC? Peak is 650 vs. 1200 but full screen is 200 vs 230. Would be really brighter an XG135LC than a 1271?

Ciao
Antonio.

Mark_A_W · Posted: Mon Nov 24, 2008 8:26 pm Post subject:

XG is subjectively almost twice as bright as a 1271.

ecrabb · Posted: Mon Nov 24, 2008 8:40 pm Post subject:

Hmm.. I don't know about that, Mark... I don't know if "twice as bright" is how I'd characterize the difference. In going from a 1271 to a G70, I can't say it seemed like brightness doubled. I wish I would have been able to measure brightness on the 1271 before I sold it, but I do know my G70 is doing ~12fl in a 10% window. That means the 1271 would have only been doing about 6 - which I'd find hard to believe - because it would have been almost unwatchable. I'd guess more like 9 or 10.

I think the peak numbers on the newer machines are in "fry the tubes" mode - which very few of us actually use.

If I were just going to give a "seat-of-the-pants" impression without actually measuring, I'd say the 1271 is more like 70-80% of the brightness of the G70 (or XG) - when you have both machines set up as you'd actually use them.

I'd say the 200 vs. 230 full-white spec is closer to the real difference between the two machines on typical high-APL material. Of course, there's a massive difference between in the two in terms of sharpness and contrast.

SC

Mark_A_W · Posted: Mon Nov 24, 2008 8:53 pm Post subject:

I went from a 1251 to a PG Xtra to a XG LC.

The 1251 was half as bright as the Xtra. Ok, three quarters maybe, but it was DIM.

A 1251/71/52/72 is just not worth playing with these days.

ecrabb · Posted: Mon Nov 24, 2008 9:13 pm Post subject:

To be fair, I did have a very nice 1271. Not mint by any means, but only ~2500 hours and pristine tubes. Did yours have a lot of hours on it? I never felt my 1271 was "dim" at all.

I don't know if I'd say "not worth playing with", either. I mean, they're only $200-300. Digital projectors in that price range are crap, so a 12xx, assuming it's in decent condition, could make a hell of a projector for somebody on a tight budget. XG's and G70's are still around a grand, so there's a lot of road between the two for a beginner or somebody on a budget.

If you can afford a nicer machine like a G70 or XG, then by all means...

SC

tony359 · Joined: 04 Aug 2006 Posts: 378

I don't think that FL are a linear unit measure and probably the "half brightness" figure is when your image is 3-4FL below.

Thanks for your opinions guy. I was watching an XG135LC but seems that if I want it I must take it "as is" without even try it!! I don't think I'll take it...

Ciao
Antonio

Mark_A_W · Posted: Tue Nov 25, 2008 6:05 am Post subject:

My 1251 was about 2000 hours I think. Hint of wear on the blue tube face.

It wasn't very bright.

My XG was $500 Smile

Antonio, is it the same XG as the one you saw? Is it expensive? I would leap at an XG135LC over a 1271.

tony359 · Joined: 04 Aug 2006 Posts: 378

The one I saw?

I mean that the buyer cannot tell me by phone the condition of the item and his condition is that I must go there, take the XG "as is" with no chance to try it even for a moment. 1350$ Smile

Ciao
A

Mark_A_W · Posted: Tue Nov 25, 2008 11:02 am Post subject:

So it's not the same XG as the one said you watched? Or did you mean you were watching the Auction? I misunderstood.

In that case offer him $200.

That's a scam in the making. Without information on the Tubes, it's just a chassis, possibly broken.

I wouldn't buy that either.

Ciao

Marco