JVC RS40/X3 Calibration Thread - Page 12

Originally Posted by GeerGuy

I'm open to suggestions on when and where to apply the screen gain. My screen is 1.0, so it has never mattered.

Right now the screen gain is only applied to the fL and nits measurements, not for Lumens. I was thinking that a person would want to know the Lumens without the screen gain, since it is a measurement of the projector light output. The fL or nits values are more associated with the entire "system".

I could just make 2 columns of numbers, 1 without gain and 1 with, and apply the gain to Lumens, fL and nits.

Thoughts?

Originally Posted by plissken99

I would have thought the added gain feature in the app tells the user how many FL he is actually seeing onscreen vs how many are coming from the projector.

Originally Posted by LarryChanin

I use Ron's Lux to Lumens calculator (as discussed in posting #2) to determine my projector's lumen output. Then I use FLBoy's calculator to estimate my screen's actual delivered gain for my actual projector and viewer locations based on my screen material. Then I plug the lumens and delivered gain (not the maximum manufacturer's quoted gain) into Ron's Simple Projection Calculator to determine the foot lamberts coming off of my screen.

Originally Posted by Shagg

If a user wants to know the FL from the screen, they're going to be a lot better off measuring it rather than trying to calculate it.

In theory you can measure the lumens directly from the projector and then calculate it based on your gain, but the problem is that the advertised gain and real world gain are not the same thing. So, any number you calculate based on the advertised gain is going to be misleading.

Since the user will have a meter in order to measure their projector lumens in the first place, it's going to be far better to use the same meter to measure the "real" FL from the screen.

Originally Posted by Shagg

Just curious, but wouldn't it be easier, and more accurate, to just measure the FL coming off of the screen?

Originally Posted by Ron Jones

The i1 Display 2 series of colorimeters (including the i1 LT) are known to have a loss of accuracy over time. Given that yours is several years old I would say that is certainly the case. X-Rite is just now releasing a new series of Colorimeters that replace the i1 Display 2 series. The new model is the i1 Display Pro III (being called i1 Display 3 by some people) and Calman will probably be offering an upgrade along with the OEM version of this new i1 model sometime soon. Note that the retail version of the "i1 Display 3" will not work with non-Xrite calibration software, such as Calman or ChromaPure (i.e., you must buy the OEM version of the i1 Display 3). The new model is said to be much more accurate and has less drift over time than the Display 2 series. The street price for the new i1 model is $269 plus Calman may charge you an upgrade fee for their software to support the new sensor, but it would probably be worth the price. The new i1 Display 3 OEM sensor in combination with Chroma Pure calibration software can be ordered thru the AV Science Store but since you already have Calman I would contact them to see what kind of upgrade they offer.

As for trying to meaure ftL off of the screen using your i1LT I have found it to be very inaccurate for that purpose. For measuring the lumens from the projector (does not involve the screen) there are low cost lux meters that work well for this purpose. See item number 5 from POST #2 of this thread.

Originally Posted by LarryChanin

Hi,

When someone is considering a new projector purchase they need to also factor in the screen characteristics. This is especially true of the RS40 in which we have to consider both 2D and 3D considerations.

In this case when we are trying to figure out the best projector/screen material combination for your configuration, it simply may not be feasible to buy multiple screens to do the measuring. I would not trust the results obtained by measuring off of those very small samples of screen material.

For folks who, for better or worse, have already committed to a projector and screen material without knowing what the foot-lamberts will be, yes measuring would be easier.

Larry

Originally Posted by Ron Jones

I don't know if Calman offers a similar service or not.

Originally Posted by plissken99

Can someone give a few more details on using the lux meter? 1, should I be using it on a 100ire test pattern screen or something?

Also is there some other way to convert lux into lumens? Because that spread sheet tell me nothing, I can't edit it in any way either since I don't own Excel.

Originally Posted by GeerGuy

I made a Window's program that will convert from measured lux to lumens, fL and nits for a given screen size.

Originally Posted by GeerGuy

I updated the app to accept a screen gain, if you need that, grab it again.

Originally Posted by LarryChanin

Hi,

The measurement(s) should be taken with the meter facing the projector. Therefore, screen gain shouldn't be a factor in converting lux to lumens.

Larry

Originally Posted by Shagg

Could have been my misunderstanding, but I thought the people talking about it above already had screens.

Yes, if you don't have a screen yet you'll need to estimate it.

Originally Posted by zbroke

Pardon the sloppy quote (cut & paste really). Previous 2 measurements I posted here"

----


- Hours: 752
- Delivery: Dec 8th 2010
- Screen size: 128"
- Throw lens/screen: 14' give or take a few inches...
- Natural mode
- Color space: normal
- Gamma normal
- High Lamp
- Iris fully open (0)
The reading at center screen shows 115 lux or 519 Lumens.

---------

- Hours: 995
- Same settings described above
- Took my measurement upon startup (no warm-up time)
- Using Lumangen mini - user setting 4 [means nothing to you guys but it's just for my reference down the line]


Center screen is showing 85.9 lux or 388 Lumens. A 34% drop in 250 hours. It caught me offguard. Gotta be honest, I'm still using Normal lamp with aperture at -7 although I'm probably opening it to -5 later tonight. I'm still very happy and my brain is certainly not registering a 34% drop.


-----------



So the latest reading is as follow:

- Same settings as above
- Hours: 1163

Center screen is showing 53 lux or 239 Lumens.

I do my regular viewing on normal lamp with iris fully open. For a while the picture quality was bugging me. So now last night at 1178 hours watching the Indiana Jones DVD I came to the conclusion that the image was too dim to appreciate this fine projector. I broke down and switched to high lamp with aperture at 12. I have a feeling the iris will get open wider sooner than I did on low lamp. But for now the PQ is back to "WOW".

So extrapolating a bit here, if I enjoyed the pic up until 1100 hrs (approx.) is it fair to assume that I could enjoy another 500 hours in high lamp mode? Time will tell. That would bring me to 1600/1700 hours. Under the 2000 hours I was hoping for but none the less not so bad.

One thing is for sure, I'm contacting Mark Haflich in the next few days to order a replacement lamp. I want one on hand for when the time comes.

Originally Posted by LarryChanin

Hi,

Thanks for your reports. They are very helpful.

With such low measurements am I correct that you are not doing any 3D viewing?

Thanks.

Larry

Originally Posted by zbroke

I haven't bought a 3D title in a while so no I'm not watching 3D. I imagine the picture would be too dim to really enjoy it but if a 3D movie I really want to see would come out, I would probably buy and watch it just the same and suffer through it.

[...]I'm contacting Mark Haflich in the next few days to order a replacement lamp. I want one on hand for when the time comes.

Originally Posted by Ron Jones

Zbroke - The industry standard for the bulb life is when the bulb light output drops 50%. It appears your bulb reached that point at near 1000 hours. I take it the bulb was kept in normal (i.e., low) lamp mode for most viewing meaning the actual bulb life was 1/3 the JVC rating of 3000 hr. for normal lamp mode or even 1/2 the JVC rating for high lamp mode.

Originally Posted by Ron Jones

I just assumed as a starting point that his projector's lumens were in the same range as several of us have measured on our RS40's when new or with very few hours on the bulb. For a single center screen measurement with the projector near max. zoom (he has fairly short throw at 14' for a 128" screen), iris fully open, natural picture mode, etc., it appears the typical new RS40 will have somewhere around 900 lumens. Mine measured a little more some owners have measured a little less. So even if his RS40 started out when new at the low end of the range (e.g., 800 lumens) then the half output point would be at 400 lumens. He measured 388 lumens at 995 hours. In reality his projector probably reached the 50% at somewhat lower hours.

Originally Posted by Ron Jones

Zbroke - The industry standard for the bulb life is when the bulb light output drops 50%. It appears your bulb reached that point at near 1000 hours. I take it the bulb was kept in normal (i.e., low) lamp mode for most viewing meaning the actual bulb life was 1/3 the JVC rating of 3000 hr. for normal lamp mode or even 1/2 the JVC rating for high lamp mode.

Originally Posted by Scott_R_K

In this Thread...http://www.avsforum.com/avs-vb/showt......they're now talking about cleaning the Prism in front of the lamp and a lot of people are seeing measurable improvements in Fl .

...and the Instructions..........http://www.avsforum.com/avs-vb/showt...0#post19405330

Scott....................

Originally Posted by Steve Smith

I have an RS20 with about 1600 hours on it and have cleaned it every 300-400 hours. At 1200 hours I decided the lamp was getting too dim for my large screen and bought a new OEM lamp. I now have about 400 hours on the new lamp. When I went to clean it there was no film or haze buildup. This leads me to believe that it was something in the original lamp housing that was offgassing. The original lamp also had the film buildup on the inside of the glass that's on front of the lamp housing.

Originally Posted by LarryChanin

I thought that problem was confined to the earlier JVC lamps and was due to some sort of off-gassing of the lamp housing, and that later replacement lamps didn't suffer from this problem.