Avi Greengart is the Research Director for Consumer Devices at Current Analysis (Mobile Phones, Connected Devices, and Digital Home). He also regularly writes for Slashgear, sporadically blogs at Home Theater View and Tweets far too often as @greengartAvi's expertise lies in understanding consumer electronics marketing, consumer behavior, and technology adoption patterns: where new technologies meet the mass market. 



Avi Greengart is an expert on the convergence of technology and entertainment: video, audio, computing, and wireless, how these are coming together, and what's likely to survive long enough to make a difference in your life.

Column #49 (7/9/03)

Digital Cameras, Notebooks, and DLP Rainbows

Centrino or No?


I am going to be purchasing a laptop for a college student and wanted to ask your advice/opinion. The college has sent us a letter that they are actively promoting Wi-Fi around campus and if students purchase a new computer they should seriously consider wireless capabilities.

One of the biggest questions I have is whether to go with a powerful processor like a Pentium 4 and buy a wireless card or go with one of these new Intel Centrino processors, which I assume you do not need an additional card, but will I lose processor speed? Speed and weight/durability are probably top priority.

AskAvi Replies:

Most college students need a notebook not just to save desk space, but for portability reasons. Full blown Pentium 4 notebooks are heavy, hot, and have poor battery life.  Yes, you can add a WiFi card to a Pentium 4 "desktop replacement notebook" (some newer models will come with WiFi capability built in), but one of the big reasons to use WiFi on a college campus is mobility.  If you can't take it anywhere because it's too heavy and the battery will run out, then there's no reason to get a wireless notebook (I suspect the college's dorm rooms are already wired with Ethernet).

Therefore, I’d go with a Pentium M Centrino, which offers fine performance for anything but hard core games or video editing. If you can swing the budget, IBM's ThinkPad T40 is widely considered the best of the bunch in terms of size/weight compromises and longest battery life (they’ve owed me a review sample for months now…) If not, Dell usually offers the best prices.

Digital Camera Recommendations


Do you have a couple of recommendations for a solid, low-cost digital camera to indulge in a new parent's photo mania?

AskAvi Replies:

There are too many models at too many price points to point to a specific camera as the right choice for a "solid, low-cost digital camera." Here are some guidelines that should considerably narrow the field:

The minimum resolution for decent pictures is 2 megapixels. 3 megapixel models gives you the ability to blow up your shot to 8x10 size, or crop out part of the shot and still have a good 4x6. 4 megapixel cameras allow you crop a shot and still print an 8x10, but no longer fit the "low cost" criteria. Your camera should have an optical zoom - digital zoom by itself is just throwing away resolution, so what you're left with looks blocky. If your camera comes with just a 8 - 32 MB memory card (most do), buy an extra 64 or 128 MB memory card.

Brand recommendations:

bulletFor ease of use and excellent results, go with a Kodak
bulletFor balance of features and excellent results, go with a Canon
bulletFor excellent pictures and sheer frustration with itty bitty joysticks and user interface, buy a Sony

Seeing Smoke, or DLP Rainbows?


I just got an NEC LT 240 projector that I am using for a flight simulator. I use Microsoft Flight Simulator 2002 and have a real cockpit in the garage.  All is great with this projector, and though I am making the image, on matte white, 1.0 gain, about 8 feet wide, the video is pretty good. some runway lights are a little blurry, especially when far away.

I just noticed today something strange and was wondering if you might know if this is that rainbow thing.  I was flying at night and down in the lower right to mid high right position on the screen, I would notice these lights kinda floating upwards. almost looked like smoke from a cigarrette just raising up from the bottom of the lower right hand area of the screen. No where else. Is that a rainbow artifact?

When I shut down the projector and had the blue background come on, there was for a few seconds, this hazy, light kinda area appear, just where this raising smoke effect was. Any ideas?  The unit is brand new and this is the first I have seen of this effect.

AskAvi Replies:

Rainbow artifacts are itty bitty colorful rainbows that appear to follow fast moving or high contrast objects on screen, particularly if you blink or move your head. They look like... rainbows, hence the name. They are quite prevalent on the LT 240, but people have different thresholds of noticing/being bothered by them.

More importantly, a "smoke artifact" is not a rainbow artifact, it's a... I have no idea, but I'd call NEC about it - they have an excellent service policy.  This could literally be smoke inside the projector being magnified by the lens.  Or a distortion somewhere in the optical chain.  In any case, not good. (In other circumstances I might have said it could simply be pixelation, but that wouldn't usually affect a solid color background like a startup screen.)

Somewhere Over the DLP Rainbow


Have you seen that rainbow effect in your DLP projector?  I'm told this problem is common in DLP projectors and while I was really enthusiastic about DLPs at first, now I'm being cautious.  Your projector seemed really good to me [he stopped by for a demo about a year ago], and I didn't notice this problem, so I was wondering if maybe your particular player managed to escape that effect.

AskAvi Replies:

Rainbows are a real problem that tends to get blown out of proportion a little.  All DLPs have the rainbow effect to one degree or another, as they rely on a single color wheel rotating through the colors, a chip with mirrors on it sync’d up with the colors on the wheel, and your persistence of vision to put it all together and create an image.  At low rotational speeds, your eye/brain isn’t completely fooled (and this can give some people pretty powerful headaches).  Most DLPs for business purposes – at least the older models – have this problem, and compound it by having a clear section in the color wheel (to boost brightness with PowerPoint presentations).  Initial industry estimates of people bothered by rainbows were pegged at 10 - 20%, but I've never seen any data whatsoever backing this up from Texas Instruments or anyone else. Good home theater projectors have faster color wheels and no clear section on the color wheel; the newest home theater-oriented DLP chips can move their mirrors faster to sync up with even faster color wheel rotations.  Some people are hypersensitive and still see rainbows, but there are always a few folks who’ll complain about anything.

My DLP projector, the Plus Piano HE-3100 (reviewed first here and again six months later) has a six section (RGBRGB), four speed color wheel – I can’t make myself see rainbows on it even if I watch high contrast material, blink while shaking my head vigorously, and whack myself with a 2x4.  Your mileage may vary.  One of the new projectors I’m expecting for review soon from InFocus is based on TI’s latest “Matterhorn” chip, and should offer a six speed color wheel.

It’s interesting to note that I’ve never heard anyone complain about rainbows on the DLP rear projection TV sets from Samsung, while rainbows – at least as an issue – are always mentioned in reviews of front projectors using the same DLP chips.  It’s possible that a front projector’s larger image size and immersive field of view have something to do with it… or it’s possible that people writing reviews of front projectors without colorimeters (guilty!) need something to write about other than “it puts up a real purty piture!”


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