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Discussion Starter · #1 ·
In case you did not see my post in the thread: http://www.avsforum.com/ubb/Forum10/HTML/007964.html


Thumper has modified an LT150. I think he had one on order from Dell and of course as soon as he gets it he takes it apart!


Anyway based on the last e-mail that I received he has worked his magic on the LT150. He has a measured contrast increase with the white segments off from ~600:1 to 1123:1 (the factory unit with white segments on measured 1000:1) It sounds like he must of incorporated his halo block as he mentioned that he has a hard time telling where the edge of the black screen border is located. He reports that the color saturation has improved, etc. (similar to my LT100).


He was going to jury the changes with a movie test last night. I am interested to hear how that came out and how the overall brightness was effected by this modification, etc.


Tell us Thumper!!! http://www.avsforum.com/ubb/smile.gif




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Gary


STOP DVI/HDCP!

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Time for me to contact Thumper and see if he'll modify one of my LT150s! Time to try white segment "on" for material without "crawlies" - 1000:1 contrast ratio!!! I might be keeping this projector longer than I thought.


Cheers,


Grant
 

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Does the LT150 allow you to adjust the Gamma of the projector? If not the reduced Black level which requires that you readjust the contrast and brightness settings of the projector will skew the Gray scale considerably. Performing a White balnce calibration will leave the midrange way out of alignment and give very poor color tracking. High contrast is only one element of a good video image. There are several other aspects to consider at the same time to make a picture look pleasing to the eye.
 

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Gary,


Your original message says a **pre-thumperized** LT150 measures 600:1 and 1000:1 with white segment off and on respectively.


Is the 1123:1 post-Thumper with white segment on only?


--Les
 

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Discussion Starter · #5 ·
The short answer is that I assume it is with the white segment totally blocked.


The long answer is as follows. Having not spoke with Thumper in detail concerning the mod I can only guess that it was similar to the mods he has performed on the LT100/UP1100 series units. This includes completely blocking the clear segment of the color wheel to improve overall black level even when that segment is turned off. As you know the light from the bulb still strikes the DMD even if the mirrors are pointing away from the lens (e.g. making black). This light is not totally absorbed by the absorbers and bounces around and some leaves the lens as uncorrelated light. This uncorrelated light increases the black level and tends to wash out the image.


Hopefully he can respond to detail what he did on his first Thumperized LT150.




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Gary


STOP DVI/HDCP!

DVI/HDCP! ~= HD-DIVX!!!

DO NOT SUPPORT JVC or anyone else who supports this!
 

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For Arrow and others interested in the LT150 (A different forum subject for a change http://www.avsforum.com/ubb/wink.gif )


It is still very early in the process of analyzing and conjuring up corrective measures to these little PJs. The contrast measurement of the unit at 1100+ to 1 was obtained with the white section off (with fully blocked clear sector) and a couple of blackout mods in the DMD chamber.


These two mods reduced the brightness of the unit by less than 0.2% from a stock unit (with white section off), well within a measurent test variance.


As a byproduct, these procedures reduced the brightness of the immediate halo by about 40% in the mannor just as Gary described it.


Next up for corrective action is the halo itself. It takes micro-masking techniques under a 100X microscope to acheive this and the only difficulty is getting repeatable results within a reasonable timeframe. To master this halo mod it will take the development of a few new techniques...


A quick check of the lens system (including restacking/reorienting) of it's elements was not helpful in affecting the throw distance. The throw of this particular unit is a function of both the main lens and the two concave collection mirrors used to present the light beam to the DMD.


Anyway, its back to the shop to continue the adventure. I will try to keep everyone informed as this progresses.


Thumper,


P.S. I have the pleasure this weekend of working on a Davis 450 http://www.avsforum.com/ubb/smile.gif

 

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Eddie,


The halo is not a problem for my because of masking. I'd be willing to have the mods without it. When do you think you'll be able to start taking units in?


I'll be away for a month so this would be good time to be without the projector.

http://www.avsforum.com/ubb/smile.gif


Steve


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Steve's Stuff
 

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Quote:
Does the LT150 allow you to adjust the Gamma of the

projector? If not the reduced Black level which requires that you

readjust the contrast and brightness settings of the projector

will skew the Gray scale considerably. Performing a White

balnce calibration will leave the midrange way out of alignment

and give very poor color tracking. High contrast is only one

element of a good video image. There are several other aspects

to consider at the same time to make a picture look pleasing to

the eye.
This subject is dear to my heart. Gamma adj is very important on a Dlp in my view. I also bet we find that most Dlps do not track D6500 very well ? The problem seems to be that all the experience and knowledge is in Crts but no one seems to be doing much in the Dlp arena.

I also agree than the contrast ratio is very important but to make a good image you need acurate primary colors and good gray scale tracking of D6500.

Where are all the ISF gurus (still on the Crt board!) I guess these guys better start brushing up on DLP tracking of gray and gamma adj. (no need for geometry adj guys)


DavidW


 

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Wow, Thumper. That's quite an improvement.


I would not need you to remove the halo either. It's invisible in my masking. But I would certainly be interested in increasing the contrast by 90% with practically no brightness loss.


BTW, is there a summary on the board somewhere of what you do to perform your magic or is that a ancient thumper secret?


Best of luck in your experiments with this projector.


--Les
 

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Discussion Starter · #11 ·
I just bumped my summary thread to the top to make it easy for you.


Concerning the gamma tables. It would appear that the LT150 stock Natural 1 table is not too bad compared to the bizare tables that came with my LT100. OF course you have individual RGB brightness and contrast that you can do some balancing for D6500. There is also a color temperature setting which I have not adjusted (played with).




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Gary


STOP DVI/HDCP!

DVI/HDCP! ~= HD-DIVX!!!

DO NOT SUPPORT JVC or anyone else who supports this!
 

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I've got my cables hanging off the computer and some prototype code ready to test (ported from Dilard). Luckily (and surprisingly), it appears that this little guy supports all of the adjustments that I would hope for in order to calibrate it for black level, white level, contrast, color correction to D65 and luminance output across the output range.


I hope to have some good news before too long.
 

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OMG! I thought my projector was very good already - and you guys are going to take it to the next level! I just want to know a couple of things:


- how does a thumpered LT150 compare to a thumpered UP1100/LT100? Thumper?

- how much are these mods going to cost me? Thumper? Milori?

- when are you guys ready to deliver the mods? http://www.avsforum.com/ubb/biggrin.gif


Gee.. I feel like a kid who's just discovered a new facet of his latest toy http://www.avsforum.com/ubb/smile.gif


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/frode
 

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Mark,


Alan Gouger mentioned in another thread today that you and

Tommyboy payed him a visit this weekend. If he still has either the NEC or Dwin CRT's set up did he demo for you? If so I would be very interested in how you liked what you saw (I know it's a loaded question but I'm interested in how you think that compares to digital).


Bob


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~ The Sultan of Cheap ~




[This message has been edited by RobertWood (edited 08-12-2001).]
 

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Hi Bob,


Yes, it was great fun to visit with Alan and "Tom Strade". We looked at a G11, G15, Seleco 200 and Dwin Transvision, although we weren't really doing shoot-outs so much as looking at add-ons, tweaks and scalers (Isco, Panamorph, Dune, HTPCs, color analyzers, etc.).


Now that you mention it, I don't believe that we fired up a CRT at all! Then again, the trip was quite short. Next trip up, I will be sure to get a CRT fired up.

Quote:
David wrote:
I also bet we find that most Dlps do not track D6500 very well...to make a good image you need acurate primary colors and good gray scale tracking of D6500
David, I hope to have some screen shots of the LT150 "before" performance (out-of-the-box) tomorrow when the projector arrives. The "after" pictures might take a little longer http://www.avsforum.com/ubb/biggrin.gif .




[This message has been edited by milori (edited 08-12-2001).]
 

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Thumper,


In your examination of the light path/lens system of the LT150, could you come up with a way to change/eliminate the angle that the image exits the lens? As it is, it leaves the lens at a 17 deg. slope, so the image moves as it expands. This is one of the major hurdles that I'm not sure I can deal with in my theater. I need to ceiling mount it, and by the time I get it back far enough for a 96" wide image, the bottom of the 4:3 image (what would be the top if table mounted) is on the floor, and the 16:9 portion is also getting too low for comfort. The clear segment masking sounds cool too!


Thanks,


Dieter
 

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Thumper,


Did you get a chance to measure the light output of the projector? I must say 1100:1 is very impressive...maybe it's time to look at side-by-side LT150's instead of a G15.


Regards,


Kam Fung
 
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