Posted on March 14, 2008 By Art Feierman
I’ve blogged a lot about Creative Frame Interpolation (CFI). This is something fairly recent to home theater projectors. Some manufacturers are on their second generation, but only about half the projectors in this report have CFI. The short of it, is that it is a process that is designed to elminate motion blur. Afterall, movies are shot at 24 frames per second. Even digital video (such as HDTV sports), at 60fps, will still have blurring when watching a fast paced sporting event, or a Transformer change shape. The concept is good to a point, but there are trade-offs.
Last year only four projectors in the report offered CFI. Now just about all of the new top of the line models offer it, and some lower priced ones as well. The least expensive CFI equipped projector this year, is the Panasonic PT-AE4000 at $1999.
This is no time for a lengthy discussion, and you will find plenty of blogs on it on our site, that really get into CFI and its trade-offs.
While a few people are really enamoured with the idea of CFI, I like it to a point. I think it’s great for most sports, and for some other content. With most CFI implementations, I don’t like the effect on standard 24 fps film based movies. At its best, it can very slightly improve some sports viewing, and improve slow panning slightly, but at its worst, it creates visible artifacts, typically, annoying ones. For you to consider: If a projector smooths out a fast action scene, the scene can become too tame. The director knows what the scene is going to look like without CFI, but if they saw the effect of CFI, they just might say “hmm, the action now seems muted.” In other words, CFI may well damage the “director’s intent.” Only the Panasonic, of these projectors, can do anything with a normal movie shot at 24fps on film, and there are times when it is over the top. One tendency is to make film movies look more like “live digital video” or as some call it, “the soap opera effect.”
On the other hand, if your projector offers CFI, no one says you have to use it for content when you don’t like the effect.
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 someone off camera is playing with the light dimmer on the wall.
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.
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