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Discussion Starter · #1 ·
Other than the obvious difference of light output what are the differences between the G20 and the G15 Dila projectors ?


I am planning on using an approximately 120" Greyhawk screen and either an ISCO II or Panamorph to replace my Sony VPH-1292.


Bryan
 

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That's the bulk of it right there, Bryan. They use the same menus, setups, etc. The main difference is optics and lamp. There might be some tweekability functions (through Dillard, etc) that others can elaborate on.


Mike
 

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Mike's right. Those are the big differences, but there is another.


The G20 uses some "next gen." electronics that are not available in the G10/G11/G15 projectors. The G20 is more like the DS1/M4000.


What this means from a practical standpoint is that you have some extra things that you may or may not need. One of them that could be quite useful is called 'User Sources', and it allows you to define brand new sources (and name them!).


In contrast, G10/G11/G15 owners have to modify the existing sources and can't change the names.


This shouldn't be a deciding factor, though. It's definitely light output that should sway you one way or the other.
 

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Contrast may be another. Apparently, the contrast level typically attainable by calibration is actually signifigantly higher on the G15 than the G20 (600:1-700:1 vs 300:1-400:1). I have a G20, and love it for the viewable image it gives me with some ambient light. However, if your primary viewing will be lights out, the G15 may give you a better picture.


Disclaimer: I haven't actually seen a post calibrated G15 to compare to my calibrated G20, these are just numbers I've heard quoted. So, I don't know how noticable the difference in contrast is, but it seems like it would be noticable.


- Dave
 

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On a 120" wide Greyhawk, I calculate about 24 foot lamberts (somebody check my math). Sounds reasonable, but the G20 might be more appropriate for that massive a screen. I think somebody around here (Dean McManus?), has such a hugey with a G15, though.
 

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I would hazard a guess that it would not be that bright. I do not think that the light output in ansi lumes will equal 1500 following calibration. I believe I heard numbers like 1000 to 1100. That would calculate to 16 to 18 ft lamberts. With good control of light this should be more than adequate.


Dave T,

what is going on with post calibration contrast numbers on the G20? You are the third or fourth person to mention 300 to 400 to one. I wonder what the light output of the G20 is post calibration? This may have a bearing on the decision. Maybe the calibrators could comment.


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STOP HDCP on DVI

Don O


[This message has been edited by Don O'Brien (edited 08-20-2001).]


[This message has been edited by Don O'Brien (edited 08-20-2001).]
 

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Assuming a 120" wide screen of 16:9 format - a raw

1500 lumens from a G15 would be somewhat less than

27 ft-lamberts.


However, if the post-calibration output of the projector

is 70% of its uncalibrated output [ I seem to remember

that as a lower limit from a previous thread. ] then the

screen would see just under 19 ft-lamberts.


That's the value you would see for a unity gain screen -

if you used a Grayhawk for improved contrast - then you

would see 17.7 ft-lamberts assuming 0.95 gain.


Greg

 

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Bryan,


I believe UserName: "Dean McManis" uses a calibrated G15 with anamorphic lens on a 13 foot wide Greyhawk Microperf! And I've heard nothing but rave reviews from fellow forum members who have been fortunate enough to experience his setup. Do a search on this forum and/or private message Dean to get the scoop. Dean is a very nice and helpful guy.


On a small note...in addition to the things others have pointed out: G20 gives off more heat. And G20 lamps cost slightly more...see the AVScience store here online.


Good luck,

Paul
 

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Some numbers to keep in mind when trying to calculate your image brightness...


Given: 1) G15 projector with true 1500 lumens output

2) a DARK theater


1500 lumens output See note #1

+33% See note #2

-04% See note #3

-20% See note #4

-05% See note #5

-10% See note #6



NOTES:


1) 1500 may not be the true light output of the projector. I don't know if JVC's specs are accurate on this one. Just remember, as the bulb ages, it continues to lose lumen output. I haven't heard what the percentages are for this one. Some bulbs loose 50% at the time they are recommended to be replaced. Maybe someone knows what it is for D-ILA bulbs.


2) Gain in lumens using an anamorpic lens like the Panamorph I (16:9) since it uses the entire 4:3 DILA panel to produce a 16:9 image. It's even a higher gain using the upcoming Panamorph II (2.35).


3) Approximate loss of lumens due to Panamorph light transmission as described by Panamorph I owner's manual.


4) Loss of 15-20% of lumens due to professional calibration according to Cliff at Progressive Labs. (quoted to me for G10, maybe it's different for the G15/G20 as talked about previously in this thread)


5) Stewart Greyhawk .95 gain.


6) Loss due to Microperf. I'm not sure about the accuracy of this percentage. Anyone?


Thought this would help you,

Paul
 

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I believe %light loss for the microperf is a real-world measurement, so it should be quite accurate.


Regards,


Kam Fung
 

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The increase attributable to the panamorph just recovers what was lost by only utilizing less than the full panel. The upshot is if you start with 1500 lumens you still have that less the pannie loss. you don't jump to 2000 lumens!


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Yes I've got a calibrated G15 on a 156" wide perforated Grayhawk with about 900 hours on the bulb and it looks quite nice.

I have an ISCO I lens which helps out, but even with normal room lights on it produces a pretty nice looking picture.


I've already corresponded with Bryan about this via e-mail as we know each other from way back, both being Sony 1292 veterans.


Contrast-wise I think that the G15 and G20 are about the same when calibrated. I'm getting about 500:1 (measured) with my G15.


-Dean.
 

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Quote:
Originally posted by Dean McManis:
Contrast-wise I think that the G15 and G20 are about the same when calibrated. I'm getting about 500:1 (measured) with my G15.
Dean:


From what I've heard, I don't believe this is so. I think my G20's post-calibration contrast of 350:1 is pretty typical, whereas G15's almost always achieve considerably higher contrast with calibration. Have you heard of a G20 getting higher contrast? I know G15's have reached up to 700:1.


Any calibrators monitoring this thread who want to step in?


- Dave

 

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Dave,


My friend has a G20 and out of the box it had great contrast. I don't know about measurement, but it seemed to be at least 400:1 before calibration.


My G15 was 250:1 and my G1000 was 60:1 before calibration. Both were around 500:1 after calibration.


Still, I don't know for sure on the G20 because his was uncalibrated and unmeasured. It could have been 350:1, but it looked VERY good.


Kam,


Unfortunately, I don't have anything to measure the FT lamberts. Subjectively, it's still fairly bright, even with the large low gain screen, but in a dark room our eyes compensate a lot.


-Dean.
 

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JVC claims that their new M2000SC model has a contrast ratio greater than 600:1. I assume that it has the same basic optical (other than lens) and electronic platforms as the M20 and G20 models. If that assumption is correct, doesn't that imply that the G20 is capable of contrast performance similar to the the G15? Or are JVC and we talking two different contrast metrics?


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Joe
 

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Discussion Starter · #19 ·
Thank you to everybody for the posts. Has anyone actually measured the post calibration contrast ratio of a G20 ?


Bryan
 

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I have measured/calibrated several G20 DILA projectors and can say without question that they do not have the same consistent out of the box performance that the G15's have. Most G15's delivered in the past eight months come out of the box with approximately 400:1 contrast ratio. They can all be improved upon significantly via a complete professional calibration yielding contrast ratios 500:1 or more depending on the individual projector.


G20's have very inconsistent performance out of the box from JVC and have measured contrast ratios that range from 250:1 to close to 400:1 . They generally tend to be at or below the 350:1 ratio claimed by JVC in their documentation as the "factory spec". They can be good performers as I have calibrated a few that have been close to 500:1 but most of them are very hard to get to even 400:1.


JVC can not explain why the G15 consistently performs better than the G20 does to me. I have asked several people (Engineers) at JVC and have come up with very few realistic reasons why it shouldn't be better. The best reason that has been explained thus far is that the optical block is not working as well as it could be. With light scatter internally, dichroics, beam splitters, mirrors, etc. their are a lot of ingredients that can contribute to a less than perfect image.


In my opinion the G15 is the best projector that JVC has offered for HT use that can be consistently calibrated to a very high standard. The G20 is an excellent projector but the QC does not seem to be as high or as consistent with this model.
 
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