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· Registered
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Discussion Starter · #1 ·
I thought adding a small list of what are the many variables that can make or break a digital projector would prove to be helpful to projector beginners here. I'm in many respect still a beginner myself, so I wouldn't mind additions from more experience folk here.

Here's my list - feel free to add in your requirements with explanations. Maybe this will help someone.

Not necessarily in order of importance.

1. Resolution (in pixels)

- Too little and you can only project a very small image, until you see pixels on the screen or the image gets fuzzy. To me a 1024 x 768 is now a minimum.

2. Light output (in Lumen)

- Too little and you need a pitch black room and too much and you can't get proper black levels easily (and you'll get a huge noise from that very powerful lamp that produces the Lumen). To me something in the range or 700-1100 Lumen is a decent compromise.

3. Contrast ratio (full on/full off or ANSI)

- For that 3D like look, improved light/shadow transitions and resistance to stray light. To me a contrast of 1:400 is a bare minimum and a 1:1000 desirable (you almost begin to see the difference between the two). Some say 1:1800 is a minimum to start approaching good CRT levels.

4. Black level (measured in?)

- High perceptual and very important to some - less to others. To me this is so important that I can't seem to like a single LCD projector I've seen, although I've not seen the latest Epsons and the like tweaked. Most LCDs produce just greys and can't resolve details in the dark end. DLPs do considerable better, CRTs are of course the best.

5. Fill factor (measured in percentages)

- Again LCDs with out staggering or MLA don't cut it for me - there is way too much empty space (dark grey lines) between pixels. This makes pixel structure very visible and IMO brings out many artifacts even better. DLPs have better fill factor, LCOS usually even better and CRT (with proper scaling) perhaps the best.

6. Color temp / accuracy (in Kelvins)

- True to life colours with vivid colours as well as natural tones. To me a 6500 K is preferable, although uniform colour accuracy across whole image can be more important than the actual Kelvin count.

7. Dark - light detail / gamma (measure in ?)

- The ability to solve finest nuances in the bottom 10% shades and the lightest 10% shades. Some projectors just crush the whole dark end and everything below last 15% becomes the same black or approximation of black. Good dark detail enables you to view movies like Dark City, Blade Runner and the like without constantly fiddling with contrast/brightness/gamma settings. A bad gamma setting causes visible compression and even banding.

9. De-interlacing (measured in chipsets :)

- A good de-interlacer will take an interlaced image and turn it from consecutive display fields to full frames (both fields displayed at the same time) for increased apparent resolution and image stability. Video material benefits especially from Faroudja DCDi based de-interlacing. PAL and NTSC need their own de-interlacing algorithms although modern chipsets usually do both these days.

10. Noise (or lack of - measured in dB)

- Nothing annoys me off more than a good projector that is visibly decent, but sounds like a buzz saw due to mechanisms inside (huge fan cooling off the lamp or the color wheel inside DLP projectors spinning at 5000 + RPM). A decent projector is no louder than 30 dB IMHO, unless you can put it really far away, the pitch is not annoying frequency or you can build a hush box. I'd realy prefer a 22 dB projector myself (having a very quiet apartment), but I doubt we'll see one in the next 5 years :)

11. Lack of artifacts (measured in AVS Forum posts)

- There are many display artifacts for various different projectors, display sources and display technologies. Some of them include:

o rainbow effect (the flashing of consecutive Red Green and Blue color fields on a screen)

o banding (the non-linear abrupt changes from one luma or color level to another - i.e. unsmooth gradients)

o dithering (noise-like structures that increases on solid areas - especially with moving images)

o stuttering (dropping of frames or uneven frame display rate that results in uneven moving display)

o flickering (usually very rapid cyclical changes of illumination levels, usually lamp or related controlling electronics being badly designed or going bad)

o aliasing problems (staircasing, interference effects like moire that show the inherent pixel structure of the image and make it less life like. Usually results of bad scaling and/or display array design or interference between video material pattern and the display device array).


Of course there are many other factors as well such as inputs (DVI, RGB, component progressive, etc), projection distance, zoom levels, optical keystone correction, adjustability (gamma, color accuracy, panel tweaking and general service menu settings) and many others.

I've mostly tried to concentrate on the visual performance here (with acoustic noise being one big exception).

Please fill in the list and point out your own important factors in deciding what is a good projector or not.

And yes, price goes without saying, but there are good/bad projectors in every price range.



· Registered
327 Posts

An excellent list. You've covered everything, and more, that any beginner would want to be concerned about. I can't think of much to add except to elaborate on some of the points you've raised. Well, there is one thing you might have missed. The range of user controls. Some projectors have a wider range of controls than others, such as colour temperature, gamma settings and individual controls for R,G & B. The more controls the better (although some might argue against this - keep it simple!). I have 2 projectors (a Sony SVGA LCD and the Hitachi SX5500W). Both, in my view, are deficient in the degree of adjustments available in RGB mode. The Sony (admittedly over 4 years old) has absolutely no colour controls in RGB. If the colours lack saturation from a particular source, the only option is to turn down the brightness and obscure shadow detail. The Hitachi is better in this regard with a red & blue control in RGB mode, but still not sufficient for some of the sources in my house, in particular DTV programms from my DGTEC set top box which are very lacking in colour saturation. Of course, the fault lies with the broadcasters and/or the STB. The STB has no colour controls whatsoever but it's the only one avaialable in Australia with an HDTV tuner.

The other issue, which is on your list but I'd like to elaborate, is black level and shadow detail. As I see it, one is caught between a rock and a hard place. If you want acceptable blacks, you have to sacrifice shadow detail. If you want shadow detail, you have to sacrifice the blacks. You can't have both with an LCD projector. On my Hitachi, the Cinema gamma setting is the most revealing of shadow detail PROVIDED the usual brightness, contrast and colour controls are at default. Unfortunately, with most sources (but not all), those controls at default produce a rather 'washed out' result. One feels the need to either increase contrast and/or reduce brightness, and as soon as you do this, you've lost some degree of shadow detail, and if there's any doubt about this, all you have to do is enter the service menu and have a look at the internally generated 29 step grey scale. The darkest 3 or 4 steps will be merged as one.

Now, this leads me on to another issue. The grey screen. This is clearly an attempt to overcome the deficiencies of front projectors, the LCD in particular. I've never had the opportunity to demo a Grayhawk or Firehawk. However, if such screens can convert the 'washed out' effect of the SX5500 in Cinema mode with default settings, to an acceptable image without the need to increase contrast or reduce brightness, then such a screen might well be worth the money.
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