DLP Projector - Color Wheel General Question - AVS Forum
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post #1 of 11 Old 09-01-2013, 08:47 AM - Thread Starter
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If a PJ has a 6 segment color wheel and says on the brochure that its 6 segment with 2x speed and mentions 7200rpm right there too. Is this actually running at 4x speed because a six segment wheel refreshes the primary colors twice during each rotation ?

The PJ also mentions that when Pal content is used with 50Hz setting on the PJ then the wheel speed goes up automatically to 3x and it mentions 10800rpm. Is that actually 6x speed due to the 6 segment wheel ?
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post #2 of 11 Old 09-01-2013, 04:53 PM
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If the 6-segment color wheel uses the arrangement R-G-B-R-G-B then this provides two full color images per revolution resulting in an effective speed that is two times the mechanical speed. However, some 6-segment color wheels use R-G-B plus secondary colors for the remaining 3 segments and in this case there is no multiplier since it takes one complete revolution of the wheel to produce one full color image.

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post #3 of 11 Old 09-01-2013, 06:33 PM
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Quote:
Originally Posted by plainman007 View Post

If a PJ has a 6 segment color wheel and says on the brochure that its 6 segment with 2x speed and mentions 7200rpm right there too. Is this actually running at 4x speed because a six segment wheel refreshes the primary colors twice during each rotation ?

The PJ also mentions that when Pal content is used with 50Hz setting on the PJ then the wheel speed goes up automatically to 3x and it mentions 10800rpm. Is that actually 6x speed due to the 6 segment wheel ?

4x Color Wheel = 7200 RPM, 5x Color Wheel = 9000 RPM, 6x Color Wheel = 10,800 RPM

Sounds like you are talking about one of the Optomas, they are likely referring to 2x in 120hz mode, but we generally think in 60hz when speaking of color wheel speeds in the forum. The manufacturers seem to love to keep color wheel speeds under wraps or let confusion about it go unanswered, as they rarely cleanly disclose the workings of the color wheel. If they give the RPM's and # of segments, then that's a dead give-a-way as to what the color wheel speed is.

Some MFR's will refer to the 60hz instead, but lately most are referring to 120hz. The color wheel speed is still spinning at the same actual RPM speed between 60hz and 120hz. When a projector is displaying 120hz, it means twice as many frames are being displayed per a full rotation compared to 60hz, that's why some call it 2x and at other times they call it 4x. Not to confuse you more, but this is a different issue from the color wheel changing speeds for 24p signals to convert to an indivisible multiplier, in this example the RPM actually changes speed.

Some wheels also have an extra segment (7-segment color wheels). Some Marantz and Planar I believe have the seventh segment, the only cheap projector I know of that also has a non-white 7th segment is the Viewsonic Pro8200, in its case it is RGBRGBY, the Y is a yellow segment which functions kind of like the white segment, except not quite as intrusive or damaging to the colors as a white segment can be.


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I think the projector in question (W2015) has secondary colors because i emailed OPTOMA and got a reply too. The brochure itself says it has a six segment wheel running at 2x but also clearly mentions the rpm as 7200rpm. But the color segments were not mentioned. So I emailed optoma and got a quick reply explaining that it has RYGWBC segments. The brochure also mentions that this PJ steps up the speed to 3x when using pal 50hz mode and also specifies the rpm changes to 10800rpm.

In the email, optoma also commented that you will hardly see rainbows in this PJ and that it would surpass my existing HD70 (which i also own) in image quality.

Given the wheel specs mentioned above, what do you feel will be the rainbow effect on this pj and how will the IQ be, since its a 3200 ANSI lumens and has a CR advertised of 15,000:1. Im buying this as an upgrade to my HD70 since i wanted a brighter image. Otherwise i am satisfied with the HD70 kind of color etc. The HD70 had seven segments running at 4x speed.
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post #5 of 11 Old 09-01-2013, 11:05 PM
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I know nothing about that particular projector, but with that many lumens on a sub-$1500 DLP, I wouldn't count on the contrast being great, advertised CR doesn't mean anything really.
However, if you need the brightness, sounds ok.

You may see rainbows, but no way to know for sure until you try it.


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post #6 of 11 Old 09-01-2013, 11:47 PM - Thread Starter
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They said they'd give me a demo. So i guess we'd just have to wait and experience it. Any suggestions on what kind of material i should run on it and what to look out for ?

My only other options are the BENQ MW519 and the BENQ W750. Benq is yet to get back to me on what sort of 6 segment wheel they have implemented.

Any ideas about those models also would be helpful.

Thanks
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post #7 of 11 Old 09-01-2013, 11:55 PM
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For rainbows, anything dark that also has bright lights in it. Car headlights at night, or for the real killer load up the HTPC and move a white mouse on a black background (though this test is a bit extreme as most people see RBE in that situation).

I would check out any dark content:
Harry Potter, Falling Skies TV series, etc...


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post #8 of 11 Old 09-02-2013, 03:50 PM
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Quote:
Originally Posted by plainman007 View Post

I think the projector in question (W2015) has secondary colors because i emailed OPTOMA and got a reply too. The brochure itself says it has a six segment wheel running at 2x but also clearly mentions the rpm as 7200rpm. But the color segments were not mentioned. So I emailed optoma and got a quick reply explaining that it has RYGWBC segments. The brochure also mentions that this PJ steps up the speed to 3x when using pal 50hz mode and also specifies the rpm changes to 10800rpm.

In the email, optoma also commented that you will hardly see rainbows in this PJ and that it would surpass my existing HD70 (which i also own) in image quality.

Given the wheel specs mentioned above, what do you feel will be the rainbow effect on this pj and how will the IQ be, since its a 3200 ANSI lumens and has a CR advertised of 15,000:1. Im buying this as an upgrade to my HD70 since i wanted a brighter image. Otherwise i am satisfied with the HD70 kind of color etc. The HD70 had seven segments running at 4x speed.

Quote:
Originally Posted by coderguy View Post

I know nothing about that particular projector, but with that many lumens on a sub-$1500 DLP, I wouldn't count on the contrast being great, advertised CR doesn't mean anything really.
However, if you need the brightness, sounds ok.

You may see rainbows, but no way to know for sure until you try it.

That projector uses a color wheel with a clear (or white) segment. This produces greatly exaggerated lumens and generally degrades the image. The newer terma/measurement "color brightness" or "color lumens" were essentially created to catch such projectors with substantially inflated white lumens output, but much lower lumens for any real world video material. Most DLP manufacturers do not publish specs. for color lumens (or color brightness) for their single chip projectors, Any 3-chip projector, be it LCoS, LCD or DLP, or even 1-chip DLPs with a RGB or RGBRGB color wheel will have the same color lumens as white lumens. Note that single chip DLP projectors that use a clear/white segment in their color wheel are far from ideal for a home theater application, but they do work for projecting powerpoint sides or text in a moderately illuminated business conference room. Also it appears the Optoma model in question really does have only a 2X color wheel and many, perhaps most, viewers will see rainbows.

For more information on color brightness - see HERE.


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post #9 of 11 Old 09-02-2013, 04:11 PM
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Most of the cheap DLP's that can do over 2500 lumens all have white segments in the color wheel, just like the Viewsonic 7820hd.


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post #10 of 11 Old 09-02-2013, 10:01 PM - Thread Starter
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Oh God. Then i think ill drop the Optoma out. Now im left with only 2 other choices either the BENQ MW519 or the BENQ W750. Do you feel one of those contenders will be a better otpion for movies. The mw519 is a WXGA resolution while the w750 is a 720p projector.

The mw519 has a RYWCBG color wheel, but i dont know the speed.
Also it states 1.07 billion colors so that means 10 bit processing ?

Members here who own the BENQ MW519 have reported that they dont see any rainbows from their movie watching experiences. Also most of my HD video material will not be dark scene oriented if that helps.
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post #11 of 11 Old 09-10-2013, 01:21 PM
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The MW519 is more of a presentation pj. According to Pjcentral “Color brightness measurements for various modes came out to a range of only 328 to 628 lumens.” And “Despite having a higher resolution than the MS517, the MW519's video quality is arguably a little worse overall.” I’d assume the W750 is more the HT pj (as it’s 720p), but I haven’t seen any specs on the color wheel or color brightness.
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