Posted on April 7, 2012 By Art Feierman
The magic of dynamic irises have dramatically improved the overall quality of home theater projectors. We’ve reached the point where most of the under $10,000 home theater projectors now have a dynamic iris to affect black level performance. Only some of the least expensive projectors and a few of the most expensive, now lack a dynamic iris. In other words, it’s a pretty standard feature at this point.
Let’s explore the purpose and the effect of a dynamic iris, on the projected image, and your viewing experience.
Since projectors cannot actually produce black, only very dark grays (varying based on the projector’s quality), intended blacks on the screen are actually that dark gray. A problem occurs when you are looking at a very dark scene. Without bright areas to cause your iris to close a bit, those blacks start looking mighty gray. When you have a dynamic iris working, on those very dark scenes it shuts down, blocking most of the light. That makes the blacks a lot darker, but slightly brighter areas still remain pretty bright. It’s a real plus. If however, your dark scene has some very bright areas, if the iris is to close down a good bit, those whites and near whites are going to get darker too. That means a bright white in an otherwise dark scene, won’t be as bright as white on a normal or bright scene. The point is, you are changing the way things are supposed to be.
That’s all just fine. The best thing about dynamic irises, is that they are the most effective on those really dark scenes, when you most need blacks to be blacker. On other, mostly dark scenes that have some very bright areas, the eye is drawn to the light, so the blacker blacks are less critical.
The other aspect of dynamic irises that I discuss is the visibility of their action. If you are looking, it’s not hard to spot their action. Of course they are idle – wide open, on bright and mostly bright scenes. When you get scene changes, though, from dark to light, or the other way around, the iris has to react to that – opening or closing. If they wait too long, they can be visible. In the case of one projector, after a change in scene brightness such as that, the iris takes seconds to react, then snaps open, or mostly closed very quickly. Very annoying. Some irises are relatively slow – they average out the change and can take a while perhaps even a second to complete an adjustment. That can cause a yo-yo type effect when scene brightness fades in and out every few seconds (happens a lot on movie credits like Superman, Star Wars, but in real content too.) One thing I look for in particular is when a scene consists of a conversation in a fairly dark room, say one with paneled walls. A person in a conversation, say wearing a bright shirt, who moves around while talking, may cause the iris to open and close slightly as the amount of brightness varies. That can make the scene come off looking like: you, watching a guy in a bright shirt talk – while so
The viewing experience: Please keep in mind, it’s my job to look into these things for you. So, while you realize that dynamic iris action can be visible, try to remember that with most of the irises on these projectors you will rarely notice their action – unless you are looking for it. I’ll let you know which ones are those more likely to be bothersome. There are only a few with issues sufficient that I recommend turning the dynamic iris off.
I spend a lot of time watching movies with dynamic irises engaged. The bottom line: While there might be a occasional noticing of iris action, with most projectors that’s a small price to pay for a significant improvement in black levels.
First, a brief on what is an anamorphic lens, and why people are interested in it.
An anamorphic lens is a second lens, placed right in front of the projector. Its sole purpose is to stretch the image horizontally (make it wider), while leaving the vertical untouched. All home theater projectors today have 16:9 aspect ratios. That’s a perfect match for HDTV content, but it is not as wide an image (relative to height) as most movies. Most movies are shot in Cinemascope – a ratio of 2.35:1 – over twice as wide as tall. When you view them on a standard home theater projector, the movie fills the screen horizontally, but leaves you with a black (ok, near black) letterbox, at the top and bottom of the screen (about 10% of the screen height for each). I’d say everyone would rather not have the letterboxing, but 99% of us get along with it just fine. Because not everything you will be watching is in Cinemascope, you still need to be able to go back to standard viewing for HDTV, movies in 16:9, and even old 4:3 (standard TV). To accomplish that, you need to move the anamorphic lens out of the way. For that reason, almost everyone going anamorphic, buys not only the lens, but a motorized sled to remove the lens from the light path when not needed.
The cost of an anamorphic lens and sled is typically $3000 – $6000 for projectors in this price range, in other words, often costs more than the projector. It also means unless you are buying one with one of the better/more expensive projectors, you are going to get a lot more bang for your buck skipping the lens, and buying a much better projector.
Of the projectors covered in this report, most do have internal support an anamorphic lens. That means you can buy the lens, etc., and it will work. That internal support consists of the correct aspect ratio for it all to look right. Any projector without that internal support, can still work with an anamorphic lens, but you’ll need to buy an outboard processor, typically from $800 on up. If you really must have an anamorphic lens, buy a projector that supports one.
Lens Memory – Anamorphic lens emulation:
Panasonic’s PT-AE4000 offers support for an anamorphic lens, but it also has something else, which is the ability to “emulate” an anamorphic lens.
The PT-AE4000 doesn’t need an anamorphic lens to put a Cinemascope image on a 2.35:1 screen with no letterboxing! This saves thousands of dollars, but has some trade-offs. Panasonic accomplishes this trick by allowing you (once set up) to touch a button to change the lens’ zoom to fill that 2.35:1 screen. Press another button and it handles your 16:9 and 4:3 content by zooming out, so the image doesn’t extend above or below your widescreen. The trick to making this work, is that you can save the two different zoom settings in a lens memory area.
The downsides are: That letterbox is still there, it’s just not hitting the screen, it’s above and below it. That shouldn’t be a problem if your wall is dark, but if not, you will see the faint light – grays, above and below the screen. Also different from using a real anamorphic lens, is that the Panasonic projector still isn’t using all its resolution for the image itself. With a “real” anamorphic lens and stretch, every pixel is in use, not just the about 80% that get used for the movie in this case. As a result, you are giving up a fair amount of brightness.
All that considered, it’s a really nice feature that allows you to go “Cinemascope” without the big expense. I had expected to see a couple more projectors this year, offering a similar solution to the Panasonic “Lens Memory”. Of course you can do the same trick with any 1080p projector with a lot of zoom range, but it is the combination of the ability to save the settings (thus “Lens memory”) that makes it convenient. I’d hate to have to get up on a ladder to change the manual zoom lens on, perhaps an Epson, or LG projector, each time I want to go from a Cinemascope movie to HDTV, or other none 2.35:1 aspect ratio content.
With the Panasonic, remember, you need the projector’s zoom to stop in two different positions. That effectively cuts down the distance range you can mount the projector, by about 50%. You need to see if you can work with the more limited placement flexibility required for Lens Memory.
I’ve been more and more enamored with the idea. I now have a 2.35:1 Stewart Studiotek 130 in my theater. I place projectors within their range, so that I can zoom for largest image and fill my screen’s width, then for HDTV or 4:3, I zoom the other way, creating a smaller image that fits vertically.
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