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blinkstar
Joined: 29 Dec 2010
Posts: 11
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| Posted: Thu Jun 16, 2011 7:34 am Post subject: How to Use Diffuser with X-Rite Eye-One Display LT? |
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I bought the X-Rite Eye-One Display LT from the link in the Grayscale for dummies guide ... My readings below 30-40 IRE are all over the map. I read that I should try taking a reading directly from the lens to compensate for this ... The LT comes with a white plastic cover described as a diffuser in the guide--do I just put that on the LT and aim it at the lens? How far from the lens should it be? I'm having trouble understanding how it works exactly as the diffuser is not at all transparent and seems to block most of the light ...
Any advice you all can give on how to calibrate directly from the projector's lens would be greatly appreciated!
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kal
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blinkstar
Joined: 29 Dec 2010
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| Posted: Thu Jun 16, 2011 3:50 pm Post subject: |
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| kal wrote: | I wouldn't point at the projector.
What projector are you using? What screen/gain? How many foot lamberts are you getting at 30 IRE? It may be that you're really low in light output and the meter's simply having problems reading.
Kal |
Thanks for responding, Kal! I think that is exactly the problem. It's a PLV-Z3 with an aging bulb, homemade gray screen. Lamberts so low I'm embarrassed to say--in the order of 2.5 ftL on an 80 IRE test pattern.
My extremely limited understanding was that, if the light output is too low to get a decent low IRE reading off the screen due to fluctuating numbers from the sensor, then pointing it directly at the lens might provide better results. Is that not true?
One more question, if you don't mind: if I'm currently getting two sets of numbers from low IRE screens, is there any reason I should trust one over the other, and if so would that be the high numbers, or the low?
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kal
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| Posted: Thu Jun 16, 2011 3:54 pm Post subject: |
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Exactly. If you're only getting 2.5 ftL at 80 IRE, down at 30-40 IRE you'd barely be getting enough for the meter to register.
I wouldn't point it at the projector. You need to take the screen into consideration. If you screen has a lower than 1.0 (unity) gain then yes, you'll get more light output when pointing at the projector but you're not measuring what your eyes are actually seeing.
You can't trust any of the numbers at low light output readings if they're not consistent.
Kal
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blinkstar
Joined: 29 Dec 2010
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| Posted: Fri Jun 17, 2011 4:29 am Post subject: |
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| kal wrote: | Exactly. If you're only getting 2.5 ftL at 80 IRE, down at 30-40 IRE you'd barely be getting enough for the meter to register.
I wouldn't point it at the projector. You need to take the screen into consideration. If you screen has a lower than 1.0 (unity) gain then yes, you'll get more light output when pointing at the projector but you're not measuring what your eyes are actually seeing.
You can't trust any of the numbers at low light output readings if they're not consistent.
Kal |
Could I consider the reverse to be true, Kal? I tried taking readings right off the lens and I do get consistent numbers with little to no fluctuation. I was hoping that improving lower IRE would fix an issue with the image being too red when I lower black level or gamma, but unfortunately I still have the same problem ...
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kal
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blinkstar
Joined: 29 Dec 2010
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| Posted: Sat Jun 18, 2011 12:46 am Post subject: |
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| kal wrote: | The reverse of what? (Sorry, I'm not sure which statement you're talking about).
Kal |
I should have made myself more clear. You wrote:
"You can't trust any of the numbers at low light output readings if they're not consistent."
So I was asking if that meant if they were consistent, could I trust them?
I just did two sets of calibrations, one off the screen, one of the lens, to my eye the one from the lens is superior, probably because the light off the screen is so weak.
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kal
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WanMan
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| Posted: Sat Jun 18, 2011 12:58 pm Post subject: |
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| kal wrote: | Exactly. If you're only getting 2.5 ftL at 80 IRE, down at 30-40 IRE you'd barely be getting enough for the meter to register.
I wouldn't point it at the projector. You need to take the screen into consideration. If you screen has a lower than 1.0 (unity) gain then yes, you'll get more light output when pointing at the projector but you're not measuring what your eyes are actually seeing.
You can't trust any of the numbers at low light output readings if they're not consistent.
Kal |
Then what can one do? Couldn't one get a sample of the screen material and move it, say 1/4 the distance from the projector whereby increasing the meter-read light by a factor of 4^2 (16)?
I understand that meters all have their limitations at the low-light end, but to just not worry about it (not that this is what you were implying, Kal) is not good either. In a pinch, if one cannot garner a sample piece of the scrren material, then moving the actual screen forward might lend a best available option.
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kal
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| Posted: Sat Jun 18, 2011 1:44 pm Post subject: |
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He should change his bulb before worrying about it I think.
He's only getting 2.5 ft/L at 80 IRE which means he's probably only getting 3-5 ft/L at 100 IRE if even that.
That's very very low and is likely unwatchable (in my humble opinion). At 30-40 IRE he's getting such a low value that the meter has a problem reading it.
For comparison sake, I get about 2.5 ft/L at 45 IRE and at at 80 IRE I'm getting 8.3 ft/L, at 100 IRE I'm getting 13.8 ft/L.
At 30 IRE I get 0.9 ft/L and never had problems reading even with an inexpensive Display LT.
Kal
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blinkstar
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| Posted: Thu Jun 23, 2011 11:30 pm Post subject: |
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I will eventually get a new bulb but I have to stick with the one I have for now. Just trying to make the best of a poor situation.
As far as taking readings directly off the lens for low IRE screens, I'm still not sure how close the meter should be from the lens.
A few feet away?
A few inches?
Anyone have any idea?
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