NEC NC2000C small iris' impact

[Ioannis Syrogiannis]

While I have an NC2000C projector that was moved to a smaller screen and figuring out the best lamp choice, I found that the 70% minimum power does not give me much choice but a 1200W lamp.
I use one excel file of NEC (B.O.S.S. 9.4, I haven't checked if there is anything more recent, but I don't think that it would help much on what I have in mind) to determine what would be enough and what would be excessive.
I thought about using a 2000W lamp and the small iris, even though I can't find it, nor any accessories' box. I guess if that is what I need, it can be obtained. I am thinking that some extra contrast wouldn't be a bad idea and the 2000W lamps are not considerably less efficient in terms of cost per hour of service life.
Yet, and that is why I am asking here, I have no data to use in order to determine if the iris will do the trick or not.
On paper, I get a flat of almost 26 ftL (common height screen) with the 2KW on 70%, so I need to know what would be the impact of the iris if I am to go for that.

Just for the sake of discussion, again on paper, with the 1.2KW I get about 15 ftL on 70% and minimal losses, so I can just stay with that.
I wouldn't consider using an iris and de-focusing also, though. I don't want to rely on calibrating with a light meter or working intuitively every time a lamp needs to be changed. Even though I understand the projector is getting old, I would prefer the installation as straight forward as it can be.

What I am wondering about is if there is any literature, or if you could share some of your knowledge/experience using the iris that would help me fill the correct numbers there and make an educated decision.
Thank you in advance.

[Mark Gulbrandsen]

Never had to use one of the IRIS in any of my installs. I always selected the correct size projector for the job.... It should not be too hard to locate an IRIS because almost none were installed and they are probably laying around the booths. I would also reccomend going with the 2kw lamp and the iris as the 2K lamp is the most cost effective. Keep in mind that you could also modify the IRIS slightly larger if need be....

[Gordon McLeod]

On small screens I made adapters to use the 1.6KW HS lamp

[Steve Guttag]

I used the iris on one screen that had the Technicolor silver screen to knock down the light. I want to say it is something like 20-30%. In terms of light and longevity...the 1.5K is going to be a lot of bang for the buck. I find that they tend to get about 90% of a 2K lamp in brightness (shorter arc) but have a lower low-end range and, you are using less electricity and heat doing it. The 1.2K lamps work on real small rooms but their decay is notably faster than the larger lamps so while they seem plenty bright on day-1...a month later, if you didn't start them in the basement (on power), really start to decay.

As to the iris (Some call them "cats eye") I think Mark is correct...there are bound to lots of them unused laying about somewhere as I think I only put in 2-3 total.

[Alan Gouger]

Aside from decreasing light output, did anyone notice if the iris also increased contrast?

[Steve Guttag]

Not significantly, if at all (I didn't measure). About the only place it could pick up contrast is in the light path between the light pipe and the DMDs. The lens and the rest of the optical path are all the same. My suspicion is that contrast improvement is minimal but probably measurable. To get any sort of significant contrast improvement you really have to go in a more holistic manner and some parts buy your more than others. The lens, for instance is a place where light can bounce around and deny contrast but if you keep the light from going to undesirable places from the lamp through the lens, you'll get your biggest boost. As an example from Barco, who cater to post houses with high contrast projectors...their new SP4K-27HC...it's a 6000:1 contrast ratio projector...BUT it its built around the SP4K-40B projector. Not only does it have a Very High Contrast lens (one level above a High Contrast lens), but its whole light path is addressed. For that, 1/3 of your light went away too. Conversely, on their standard SP4K-C projectors (with the "B") lens holder, you can put in just a normal High Contrast lens to kick the 4K image from 2300:1 up to 3000:1 and only pay a 20% light penalty. That is with RGB lasers though. The case is far worse with their Xenon systems, in terms of light loss.

Again, since I was mostly using the iris to knock down the light, and the screens I used them on were, typically, "silver", contrast wasn't my concern. Also, back then, the 1.2K and 1.5K lamps were not an option. The iris came with the projector and was a relatively quick thing to put in the light path.

Of possible interest, Christie offered (and possibly still does) a "kit" of iris (cats eye) for their S2 projectors like the CP2220 so one could chose the one that gets the light level in the range desired. They were not cheap though. Why they are called "cats eye" becomes apparent when you see one.

[Carsten Kurz]

Alan Gouger built an iris into his (Barco) lens himself and got a considerable contrast boost (and light loss).

[Steve Guttag]

Define considerable and put some numbers in there and how it was specifically measured.

[Carsten Kurz]

I think that was around 7 years ago:

http://www.film-tech.com/cgi-bin/ubb...001781/p1.html

[Steve Guttag]

Apparently, I was vocal about it back then too!

[Alan Gouger]

I have had no experience with the NEC, that is why I am asking. If we're talking an iris in the light pipe, I believe it gets placed in a different location compared to the Barco, right after the lamphouse.

[Gordon McLeod]

It is a cat's eye shapped apperture plate in effect

[Steve Guttag]

It gets placed right before the fold mirror.