this how i basically understand it...

when it comes to front projectors contrast ratio really isnt a big deal unless the room is in complete darkness. With even the smallest amount of ambient light there is no difference between a 50:1 image and a XXXXXXX:1 image.

before we get any further is that correct? half true?? true with other display devices?? If the above is true than why is it even mentioned in marketing, ads, and so on?? Just to try and grab peoples attention with large numbers??

I am looking to replace a NEC LT35 (dlp, 3000L,1600:1) with a mitsu xl650u (lcd,4200L,600:1) in an office for data/presentation (controled lighting but will always have ambient light). How would any of this if we were talking about a home theater projector.

While i am typing... is it true that an LCD projector would do better in a setting like this than a dlp. I really dont have any experience with LCD projectors but i understand what some people are talking about when they talk about the "softness" of a dlp picture.

In that environment what you want to look for is Lumen's and if you still want a decent image then look for high ANSI as well (usually the two do not go hand in hand however unless you are talking megabuck projectors) .

Oh and that above statement is true to an extent , even small little LED's on AVR's/DVD Players/Amps/etc. can reduce CR (ambient light can pretty much destroy it , especially if we are talking direct sunlight) .

-- Jason

before we get any further is that correct? half true??Really depends on how much light, so I wouldn't say it is true when people make comments like that and say "even the smallest amount of ambient light". As an example, I have a room that is mostly black velvet with a light bit of the floor at the back being light colored and 2 lights pointing straight down at the back of the room. I have short 40 watt bulbs in each of those lights and they are short enough with the sides being dark inside the light fixtures that the light directly from them lands a few feet in front of the screen at the closest, where the floor has black velvet. So, they light up the back of the room, but there is no direct light from them to the screen. Only reflections from them. My equipment for measuring only goes down so far, but based on my measurements it looks like I could maintain well over 1000:1 on/off CR off the screen even with the lights on to read, eat, etc. I also have little lights on my equipment, but my equipment rack is pointed sideways and those don't shine directly on the screen. I still cover things like the display on my receiver with neutral density material so it doesn't shine as much light where I am, but can still read it.

I realize the above isn't standard, but is an example where even two 40 watt bulbs leave room for reasonable CR off the screen. This is also with a High Power screen. With a different screen, like one of the black screens that blocks off angle ambient light even more, it could be possible to get even more CR off the screen with lights on.

Now if you take your equipment and point it straight at the screen with lights on it then you could kill CR down to the level you mentioned, but even then it wouldn't be guaranteed to go that low. Some equipment has bright blue lights (like a DIRECTV HD DVR) and those could kill CR a lot.

Just in case it isn't clear, even a white room could maintain huge on/off CR if you don't have other lights lighting up the screen. Basically, the level of the screen with the projector off is the darkest it will ever go and if the room is dark enough with the projector off that you can't see the screen, then even 30k:1 on/off CR wouldn't be killed by the room.

--Darin

Really depends on how much light, so I wouldn't say it is true when people make comments like that and say "even the smallest amount of ambient light". As an example, I have a room that is mostly black velvet with a light bit of the floor at the back being light colored and 2 lights pointing straight down at the back of the room. I have short 40 watt bulbs in each of those lights and they are short enough with the sides being dark inside the light fixtures that the light directly from them lands a few feet in front of the screen at the closest, where the floor has black velvet. So, they light up the back of the room, but there is no direct light from them to the screen. Only reflections from them. My equipment for measuring only goes down so far, but based on my measurements it looks like I could maintain well over 1000:1 on/off CR off the screen even with the lights on to read, eat, etc. I also have little lights on my equipment, but my equipment rack is pointed sideways and those don't shine directly on the screen. I still cover things like the display on my receiver with neutral density material so it doesn't shine as much light where I am, but can still read it.

I realize the above isn't standard, but is an example where even two 40 watt bulbs leave room for reasonable CR off the screen. This is also with a High Power screen. With a different screen, like one of the black screens that blocks off angle ambient light even more, it could be possible to get even more CR off the screen with lights on.

Now if you take your equipment and point it straight at the screen with lights on it then you could kill CR down to the level you mentioned, but even then it wouldn't be guaranteed to go that low. Some equipment has bright blue lights (like a DIRECTV HD DVR) and those could kill CR a lot.

Just in case it isn't clear, even a white room could maintain huge on/off CR if you don't have other lights lighting up the screen. Basically, the level of the screen with the projector off is the darkest it will ever go and if the room is dark enough with the projector off that you can't see the screen, then even 30k:1 on/off CR wouldn't be killed by the room.

--Darin

Nothing to add to this thread. I just wanted to say your post count is the largest by far that I have seen on this site.

Here's an interesting read on the subject:

http://www.practical-home-theater-guide.com/contrast-ratio.html

Here's an interesting read on the subject:

http://www.practical-home-theater-guide.com/contrast-ratio.html
That is fairly old and unfortunately I think it is somewhat misleading. I always wonder about people who act like ANSI CR or on/off CR is an either or, like their:
ANSI Contrast represents a more fair way to test contrast ratio as the presence of black and white at the same time is closer to the real world environment rather than the all black or all white image used during the full ON/OFF contrast measurement. This renders the average reading obtained from the ANSI Contrast more realistic.at least partially does. I know there are people who think ANSI CR tells us about mixed images and on/off CR tells us just about blackouts, but they don't understand the subject matter. ANSI CR and on/off CR tell us different things. ANSI CR is an indicator of the washout effect and on/off CR of the raised black floor effect. Both matter and neither is a substitute for the other. Also, neither is more realistic than the other, but once you have over say 300:1 ANSI CR, I would say that improving on/off CR becomes more important to image quality (and is even more important to perceptions in many cases even with lower ANSI CRs, like 130:1).

Greg Rogers recently reviewed the Marantz 11S2 DLP, which had around 8k:1 on/off CR and I think well over 500:1 ANSI CR. He compared this to the JVC RS2 that was more like 30k:1 on/off and 300:1 ANSI CR. For the images he tested the RS2 had the image depth advantage from CR in the images, overall. Part of this may have been because the RS2 has enough on/off CR to support a 2.4 gamma, where a lower on/off can create problems with gammas above 2.2, although the Marantz also didn't have a setting beyond 2.2 for gamma.

Back to the article. This part:
The complete absence of stray light in a room is a critical issue when it comes to contrast performance. In everyday life, this is an extremely rare situation unless one is making use of a controlled environment, such as that of a dedicated home theater with black painted walls.This implies that dark walls are needed to get high on/off CR. This isn't true. It is ANSI CR that requires dark walls more. A white room can support on/off CRs over a million to one if there aren't other lights.

One thing to keep in mind with the candle is that their statement that a candle would be one LUX isn't true. A LUX is a lumen per square meter, so it depends on how far the light is from the screen, where it is pointed, and whether there is anything between it and the screen. My 40 watt bulbs are likely much brighter than that candle, but their statement about 500:1 being the same as 10k:1 isn't true for even both those 40 watt bulbs being on in my room.

Their use of the Contrast Sensitivity Function (CSF) makes me think they don't understand it. In fact I believe I sent an email to them after reading their article with bogus claims about it and they tried to make it better, but still don't understand it IMO. The CSF measures the least amount of CR you can see (white on off-white) not the most. The score of 100 in the CSF is a CR around 1.1:1 not a CR of 100:1. And in certain conditions where our eyes are not capable of seeing something, it is improving the CR of the projector/system that is needed to allow us to see it.

That article is somewhat better than when I first read it, but I still think many people would walk away thinking both that ANSI CR matters more than on/off CR and they need dark walls to take advantage of on/off CR. I spent a lot of time writing this article:

http://www.hometheaterhifi.com/volume_13_2/feature-article-contrast-ratio-5-2006-part-1.html

partially because there is so much misinformation out there about CR.

Fortunately, multiple manufacturers have continued to give us better and better on/off CRs even as some in the industry have disparaged that. And many of us have seen the improvement those better on/off CRs have brought (in environments where it matters, like without lighting up the screen with other things and killing the CRs).

--Darin

Here's an interesting read on the subject:

http://www.practical-home-theater-guide.com/contrast-ratio.html
One more thing about that article. The part that says:
So what's the whole discussion here?

Do not get carried away with big contrast numbers - the eye dynamic response is the limiting factor.is false. The person or people who wrote this must not have understood what they were reading about the eye's capabilities (like they didn't know what CSF actually measures). The whole point of high on/off CR is for the dark images where our eyes are much more capable with their dynamic range than any digital projector with 30k:1 or under on/off CR. As I mentioned in my article, with a CRT setup around 700k:1 on/off CR in a largely white room, it only took a few seconds to see the screen on an extended blackout. And with an image with 5%stim as the highest, some video black, and strict 2.5 gamma, 30k:1 on/off CR would provide about 17:1 simultaneous CR in that image. Much less than we could see. 10%stim and the same would be around 95:1 simultaneous CR. Not bad, but we could probably perceive the difference if it was higher there.

It has taken some time for displays to come out or be demoed that would show how ignorant some of the claims out there for the last few years have been. For instance, the Brightside High Dynamic Range displays where people could see how possible it was to see visual improvement from much better CRs. And then the Pioneer plasma demo at CES where they showed that even with the high simultaneous CRs they can get with current plasmas, with one that could go way higher the difference was obvious with things like an object in the center of the screen and video black around it.

The projectors discussed here have a ways to go in on/off CR before the dynamic range of our eyes limits us so that we couldn't see improvement beyond that. Of course, for situations where they are setup so that they get that on/off CR off the screen.

--Darin

Well Darin, if you would make your article easier to find, I would be glad to reference it!

:D

I've bookmarked it for later references, thank you.