Using the CA813 light meter to measure your front projector - Page 4 - AVS Forum
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post #91 of 111 Old 10-30-2009, 06:32 AM
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I think as Tom and Alan pointed out, his meter is accurate. What it comes down to is tolerances on the CA813 I don't think are all that tight, especially in the low level readings. In experimenting between various meters, including my CA813 and T10, we found that the CA813 would give varying results. So while a specific CA813 and technique could give comparison amongst itself, I personally concluded that it may/may not be accurate enough for posted results, thus my reason for switching to the T10.
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post #92 of 111 Old 11-13-2009, 08:01 AM
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I just borrowed a CA813 from work and took these measurement yesterday evening. Notice how much the iris affects the On/Off ratio.

Epson 6500 UB - calibrated
Carada 118" BW (41.4 ft2), Gain 1.2

Projector output Lumens
Natural High Lamp (380 hours) 293
Dynamic Low Lamp (380 hours) 423

On/Off Contrast ratio
Natural High Lamp NO Iris 2,443:1
Natural High Lamp Iris NORMAL 14,810:1

Dynamic Low Lamp NO Iris 3,333:1
Dynamic Low Lamp Iris NORMAL 76,540:1 (Average of 3 readings)

ANSI Contrast ratio
Natural High Lamp NO Iris
Projector 252:1
Screen 131:1
Natural High Lamp Iris NORMAL
Projector 253:1
Screen 133:1

Dynamic Low Lamp NO Iris
Projector 256:1
Screen 125:1
Dynamic Low Lamp Iris NORMAL
Projector 255:1
Screen 126:1

Any comments/suggestions are welcome.

BTW I think I got some good consistent reading with this meter (it is new), as none of the readings seem wildly different as I measured these several times.
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post #93 of 111 Old 11-13-2009, 11:07 AM
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Quote:
Originally Posted by Knd View Post

BTW I think I got some good consistent reading with this meter (it is new), as none of the readings seem wildly different as I measured these several times.

The meter can be very stable and you will be fine comparing different projectors to each other in your room. Where they differ are between each other or other meters. My CA813 while stable was off to Jasons and Jasons was off to Greg Rogers. Darin ended up getting rid of his. We now use the Minolta T-10.
For the money it gets you close enough. I would only spend additional money if you decided to compare numbers with other reviewers.
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post #94 of 111 Old 11-13-2009, 12:16 PM
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Quote:
Originally Posted by Alan Gouger View Post

I think you got lucky in the draw
Early on Jason started out using this meter and wondered why his numbers where different then others on this board and took slack for his reviews. I then bought the same meter based on his and others recommendation at the time. It was only then we found both meters delivered numbers far enough apart per same projector. We had no clue which was correct. At the time I did not have my spectro as reference. We both ended up giving our CA813 away. We now use the Minota T-10.

It is possible that I just got a good one. I have now tested it against the Orb spectro, the Chroma 5 colorimeter, and even the Minolta LS-100. I get very consistent results.

One thing to keep in mind when using it with front projectors is that its sensitivity is high enough that the results are affected by very small changes in the angle of acceptance and tiny amounts of ambient light in the room, such as LED readouts on equipment. My tests involved placing it directly up against a flat panel where those issues were not a factor.

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post #95 of 111 Old 11-14-2009, 12:05 AM
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IIRC, William Phelps posted once that he took a CA813 apart and found that the way it's calibrated is through a cheapo potentiometer which is something notoriously prone to drift. Not to say that it can't be accurate, I guess you get what you pay for
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post #96 of 111 Old 05-30-2011, 03:22 AM
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Quote:
Originally Posted by Rob Tomlin View Post

I finally got around to measuring the on/off contrast ratio of my current 720p DLP projector (Dwin TV3).

My fc reading was 553 = 5952.44 lux.

A fc rating of 553 seems incredibly high. Considering the cinema standard brightness is about 16fc...
Sure this was measured right?
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post #97 of 111 Old 05-30-2011, 07:20 AM
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I don't usually measure on-off at the screen distance. The meters aren't as accurate down low when doing the dark reading. If you move it close to the PJ, you sense a larger "beam" percentage and you raise the level of the dark reading. That would make the numbers read much higher than the illuminance value of 16fc, or the luminance value of ~16ftL (off the screen)
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post #98 of 111 Old 06-01-2011, 07:14 AM
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I just did measurements of Lumen output of my Home Cinema 1080 (actually called TW980 here but I think it's the same model) and this is what I got (separate Footcandle and Lux measurements using my light meter at screen).

The screen is 92" diagonal 16:9 with 1.0 gain which has area of 24.9sqft. The projector throw is 15ft.

Using this: lumens = fc * square feet of screen, I get below lumen measurements:


Dynamic
10.3fc (110.8 lux) = 256.5 lumens

Living
6.9fc (75 lux) = 171.8 lumens

Natural
3.3fc (35.8 lux) = 82.17 lumens

Theatre
3.0fc (32.6 lux) = 74.7 lumens

Theatre Black 1
3.7fc (40.1 lux) = 92.13 lumens

Theatre Black 2
2.0fc (22.6 lux) = 49.8 lumens


Can someone tell me what's wrong with these calculations?
Where is the 1200 lumens this projector is supposed to be rated at?

The thing is that in dynamic mode (which i use all the time because the other modes are too dim) the 100% white is perfectly bright in dark room and from test patterns the contrast is great too, but is it really only 256 lumens?

p.s. I have projector since December 2008 and this is my second bulb - it has a couple hundred hours on it I think now. I always use Dynamic mode. First bulb lasted 1272 hours on nothing but dynamic mode.
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post #99 of 111 Old 06-01-2011, 07:38 AM
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Quote:
Originally Posted by geogan View Post

I just did measurements of Lumen output of my Home Cinema 1080 (actually called TW980 here but I think it's the same model) and this is what I got (separate Footcandle and Lux measurements using my light meter at screen).

The screen is 92" diagonal 16:9 with 1.0 gain which has area of 24.9sqft. The projector throw is 15ft.

Using this: lumens = fc * square feet of screen, I get below lumen measurements:


Dynamic
10.3fc (110.8 lux) = 256.5 lumens

Living
6.9fc (75 lux) = 171.8 lumens

Natural
3.3fc (35.8 lux) = 82.17 lumens

Theatre
3.0fc (32.6 lux) = 74.7 lumens

Theatre Black 1
3.7fc (40.1 lux) = 92.13 lumens

Theatre Black 2
2.0fc (22.6 lux) = 49.8 lumens


Can someone tell me what's wrong with these calculations?
Where is the 1200 lumens this projector is supposed to be rated at?

The thing is that in dynamic mode (which i use all the time because the other modes are too dim) the 100% white is perfectly bright in dark room and from test patterns the contrast is great too, but is it really only 256 lumens?

p.s. I have projector since December 2008 and this is my second bulb - it has a couple hundred hours on it I think now. I always use Dynamic mode. First bulb lasted 1272 hours on nothing but dynamic mode.

Your calculations are correct. So if your reading for the fc or lux were done correctly then your projector is quite dim. Was the replacement bulb a Epson unit or was it a generic OEM bulb? Bulbs normally dim over time and a drop of 50% is typical after perhaps 1000+ hours of use, but it looks like you are getting 25% (or less) of what would be expected with a new bulb (or a bulb with low hours).

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post #100 of 111 Old 06-01-2011, 11:45 AM
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What are you using for your white 100% pattern?
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post #101 of 111 Old 06-01-2011, 02:12 PM
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Quote:
Originally Posted by GetGray View Post

What are you using for your white 100% pattern?

In addition to using a 100% white test pattern, he should first calibrate his projector for the black and (especially) white reference levels using the test patterns from a calibration disc such as the "AVS HD Calibration Disc" (freeware image file is available for download and you then burn you own DVD on a PC). As a point of comparison, I have the next later generation Epson (model 6500UB) and with 500 hours on the lamp it still measures almost 500 lumens in best D65 calibrated mode (at screen center) and well over 1000 lumens in dynamic mode.

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post #102 of 111 Old 06-02-2011, 05:41 AM
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Originally Posted by Ron Jones View Post

Your calculations are correct. So if your reading for the fc or lux were done correctly then your projector is quite dim. Was the replacement bulb a Epson unit or was it a generic OEM bulb? Bulbs normally dim over time and a drop of 50% is typical after perhaps 1000+ hours of use, but it looks like you are getting 25% (or less) of what would be expected with a new bulb (or a bulb with low hours).

My meter can read in fc or lux and i took all readings in both modes just to be sure. The room was completely dark with projector a fairly long 15ft throw away so there wasn't any problems with uniformity as when it is in full wide and up as close as possible to screen (i was amazed how bad uniformity was from centre to left, right, top, bottom when i tested with projector on table as close as possible at full wide). At 15ft distance the readings were within 0.3fc of each other at any position on screen.

Yes I used the "AVS HD Calibration Disc" burned onto a blu-ray re-writable disc running on PS3 slim. I can't remember the name of the calibration section but it was the one where it shows the 25%, 50%, 75%, 100% colours and then white. I used the 100% white fullscreen one.

This is how i measured - Set pj to correct mode eg. Dynamic. Place measuring probe against screen with white dome facing back to projector. Correct?
The readings were stable and consistent and as i said more-or-less uniform no matter which position i tried on screen.

I bought the replacement bulb here:

http://www.justprojectorlamps.co.uk/...W980-vprf.html

and at the time of order (19th October 2009) there was no option of original or compatible bulb as there is now. I assume it was original because it had Epson instructions leaflet with it.

I think there could be 1000 hours on this bulb now (forgot to check exact number) but you can see from readings above how dim the Cinema modes are and always have been, so much so that i couldn't understand how other users and reviewers were recommending these modes for normal film viewing.
I just needed to be sure I wasn't just reading/calculating lumens wrong.

p.s should I have had 2000 hours or 3 year warranty on these bulbs?
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post #103 of 111 Old 06-02-2011, 06:46 AM
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Quote:
Originally Posted by geogan View Post
My meter can read in fc or lux and i took all readings in both modes just to be sure. The room was completely dark with projector a fairly long 15ft throw away so there wasn't any problems with uniformity as when it is in full wide and up as close as possible to screen (i was amazed how bad uniformity was from centre to left, right, top, bottom when i tested with projector on table as close as possible at full wide). At 15ft distance the readings were within 0.3fc of each other at any position on screen.

Yes I used the "AVS HD Calibration Disc" burned onto a blu-ray re-writable disc running on PS3 slim. I can't remember the name of the calibration section but it was the one where it shows the 25%, 50%, 75%, 100% colours and then white. I used the 100% white fullscreen one.

This is how i measured - Set pj to correct mode eg. Dynamic. Place measuring probe against screen with white dome facing back to projector. Correct?
The readings were stable and consistent and as i said more-or-less uniform no matter which position i tried on screen.

I bought the replacement bulb here:

http://www.justprojectorlamps.co.uk/...W980-vprf.html

and at the time of order (19th October 2009) there was no option of original or compatible bulb as there is now. I assume it was original because it had Epson instructions leaflet with it.

I think there could be 1000 hours on this bulb now (forgot to check exact number) but you can see from readings above how dim the Cinema modes are and always have been, so much so that i couldn't understand how other users and reviewers were recommending these modes for normal film viewing.
I just needed to be sure I wasn't just reading/calculating lumens wrong.

p.s should I have had 2000 hours or 3 year warranty on these bulbs?
I assume you did set the reference white level using the flashing bars test pattern on the AVS disc and adjusting the projector's contrast control before you measured the light output. It does appears you did the measurement correctly. As for the bulb warranty, in the USA the replacement bulbs typically only carry a 90 day warranty and the original bulb that comes in the projector typically no more than 1 year. If you are in the UK the warranty may be longer so you should check the paper work that came with the replacement bulb.

I guess the most basic question is how bright was the projector when it was new? Does it seem much dimmer now? Very few AVS members would want to use the Dynamic mode on the Epson projectors because it has poor colors and the other more accurate modes should still provide adquate light output for use on moderate size screens in rooms with good light control. I use my 6500UB on a 120 inch screen with a gain of 1.1 and I have calibrated for grey scale/color points/gamma/etc. and with 500 hours on the bulb it still is bright enough (with about 500 lumens output measured from the projector). I realize the 6500UB series would be expected to have a little more light output than your earlier model, but if your projector has always been dim (even when new) then perhaps there is a some problem with the projector itself and not just a bulb issue.

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post #104 of 111 Old 06-02-2011, 09:58 AM
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Originally Posted by Ron Jones View Post
I assume you did set the reference white level using the flashing bars test pattern on the AVS disc and adjusting the projector's contrast control before you measured the light output. It does appears you did the measurement correctly. As for the bulb warranty, in the USA the replacement bulbs typically only carry a 90 day warranty and the original bulb that comes in the projector typically no more than 1 year. If you are in the UK the warranty may be longer so you should check the paper work that came with the replacement bulb.

I guess the most basic question is how bright was the projector when it was new? Does it seem much dimmer now? Very few AVS members would want to use the Dynamic mode on the Epson projectors because it has poor colors and the other more accurate modes should still provide adquate light output for use on moderate size screens in rooms with good light control. I use my 6500UB on a 120 inch screen with a gain of 1.1 and I have calibrated for grey scale/color points/gamma/etc. and with 500 hours on the bulb it still is bright enough (with about 500 lumens output measured from the projector). I realize the 6500UB series would be expected to have a little more light output than your earlier model, but if your projector has always been dim (even when new) then perhaps there is a some problem with the projector itself and not just a bulb issue.
Yes I did the black/white levels - they were alright - i left the white slightly less bright as they say on video so you can see more grey stripes flashing up to 250.

I seem to remember on the original bulb it dimmed a lot before it went and then the second bulb was brighter when I installed it, but I never had a lightmeter at that time so it is highly subjective how much brighter it was. I would love to be able to measure a brand new bulb in it now to see.

What I was really wondering was were my measurements correct after seeing all the www.projectorreviews.com reviews and lumen measurements in the reviews of newer Epsons.

I mean according to http://www.projectorreviews.com/epso...erformance.php it looks like the 8700UB is 4 times brighter than mine in Dynamic mode (1100 vs 256 lumens) and nearly 9 times brighter in my preferred quiet Cinema Black 2 mode (380 vs 50 lumens)

It appears that the 8700UB's Cinema Black 2 mode - it's DARKEST mode - is much BRIGHTER than my BRIGHTEST mode!! (380 vs 256 lumens) How could this be possible?

Does 9 times as much lumens appear 9 times brighter or is it some sort of logarithmic scale?

Also if you look at the bulb accessory page of Epson projectors you will see there is basically only two bulbs they use - the "49" and the "39". The 49 is used in the top ones and mine is the 39. There can't be that much difference between them.

It's also interesting to note that the SAME 49 bulb is used in three different projectors that are marketed as being 1600, 1800 and 2000 lumens light output respectively.... is Epson pulling more fast ones

re: warranty see here on EU site http://www.epson.eu/Projectors/Epson...500/Tech-Specs - it says projector & lamp are 5 years - probably only if you buy from official Epson dealer. Thing is they appear to be WAAAY dearer than EBay sellers from USA... eg. 4,891.21 USD is UK price of EH-TW5500 which is equivalent to PC 9500 model in USA...
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post #105 of 111 Old 06-04-2011, 06:50 AM
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Quote:
Originally Posted by geogan View Post

Yes I did the black/white levels - they were alright - i left the white slightly less bright as they say on video so you can see more grey stripes flashing up to 250.

I seem to remember on the original bulb it dimmed a lot before it went and then the second bulb was brighter when I installed it, but I never had a lightmeter at that time so it is highly subjective how much brighter it was. I would love to be able to measure a brand new bulb in it now to see.

What I was really wondering was were my measurements correct after seeing all the www.projectorreviews.com reviews and lumen measurements in the reviews of newer Epsons.

I mean according to http://www.projectorreviews.com/epso...erformance.php it looks like the 8700UB is 4 times brighter than mine in Dynamic mode (1100 vs 256 lumens) and nearly 9 times brighter in my preferred quiet Cinema Black 2 mode (380 vs 50 lumens)

It appears that the 8700UB's Cinema Black 2 mode - it's DARKEST mode - is much BRIGHTER than my BRIGHTEST mode!! (380 vs 256 lumens) How could this be possible?

Does 9 times as much lumens appear 9 times brighter or is it some sort of logarithmic scale?

Also if you look at the bulb accessory page of Epson projectors you will see there is basically only two bulbs they use - the "49" and the "39". The 49 is used in the top ones and mine is the 39. There can't be that much difference between them.

It's also interesting to note that the SAME 49 bulb is used in three different projectors that are marketed as being 1600, 1800 and 2000 lumens light output respectively.... is Epson pulling more fast ones

re: warranty see here on EU site http://www.epson.eu/Projectors/Epson...500/Tech-Specs - it says projector & lamp are 5 years - probably only if you buy from official Epson dealer. Thing is they appear to be WAAAY dearer than EBay sellers from USA... eg. 4,891.21 USD is UK price of EH-TW5500 which is equivalent to PC 9500 model in USA...

9 times more lumens will appear perhaps 3 times as bright. As for why different models of Epson projectors that use the same bulb are rated with different lumens output - the bulb's light output is only one factor in the lumens output from the projector. Other factors include the specific LCD panel characteristics (size, fill factor, etc.), the f-stop of the lens, the specific projector default settings for color gains in the brightest mode (e.g., Epson's Dynamic mode), etc. If your projector/bulb is still under warranty then you should phone Epson and see what they can do.

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post #106 of 111 Old 08-18-2013, 07:14 PM
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I realize I'm resurrecting a long dormant thread, but hopefully someone's still paying attention.

I'm interested in getting a light meter mainly to satisfy my own curiosity as to the relative brightness of different projectors in my own theater. (The one I have now, a few options I'm considering as alternatives, etc.) I have no desire to do any serious calibration with it, nor do I particularly care if it's reference quality, so the CA813 was where I was looking. I also do not expect that I would ever use it to calculate CR. Well, maybe I would just for kicks if I have a meter that I thought would do a good job of it, but from reading this thread, it looks like the reliability of the CA813 on the low end is questionable enough that I'm not sure how accurate the CR results would really be. Beyond that though, I simply care more about checking the brightness of these projectors than the contrast ratios.

Which brings me to my question. When looking at the CA813 online, there's another meter I saw that is even cheaper (Dr. Meter Digital Light Meter LX1330B). Besides kind of wanting to not buy it just because they named it Dr. Meter, I can't help but wonder if it would be fine for my purposes at a fifth of the cost of the CA813. It's hard to tell from the specs on the site I was looking at, but I'm guessing that maybe it's only accurate to 1 lux, as opposed to .01 lux. Unless I'm totally misunderstanding how all of this works, that seems like it would be a major problem for measuring CR, but not really that big a deal for measuring lumens at the top end for overall brightness.

Anyone care to give their thoughts on the use of this meter to simply compare between projectors (or to check bulb dimming over time on a single projector) in my own setup?
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post #107 of 111 Old 08-18-2013, 07:37 PM
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I have 2 Minolta T-10's which are better meters. I'd be interested in selling one of them. It would be a little more than the CA-813 new though. Send me an Email or PM if interested. scott@techht.com
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post #108 of 111 Old 08-18-2013, 07:41 PM
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Thanks Scott, and I'm sure someone will jump on it, but for my purposes given that I'm inquiring into an option that's only a fifth of the cost of the ca813, I'm probably not looking to spend any more than I would for the ca813.
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post #109 of 111 Old 08-19-2013, 11:51 AM
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I doubt that any of the inexpensive lux meters (say under $500) are sensitive enough or accurate enough at very low light levels to do a contrast measurement on any of the projectors that have a high CR. They may be OK for a DLP with only 3000:1 CR but will not produce an accurate measurement for a JVC with 50,000:1 CR.

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post #110 of 111 Old 08-19-2013, 03:16 PM
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I would think most folks buying light meters like a CA813 are interested in measuring new lamp brightness, and then the lamps eventual dimming. I've never bothered to measure contrast with mine.

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post #111 of 111 Old 08-19-2013, 03:27 PM
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Quote:
Originally Posted by Craig Peer View Post

I would think most folks buying light meters like a CA813 are interested in measuring new lamp brightness, and then the lamps eventual dimming. I've never bothered to measure contrast with mine.
Yeah, that's what I'm looking to do (as well as comparing projectors). I went ahead and ordered the cheap Dr. Meter, because at the price it's almost a throwaway if it's no good. We'll see how it goes.
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