Calibration meter shootout - Page 7

Sorry for being anal but ..

First of al it's Hygroscopy not hydroscopy



Second, the filters aren't glass but mere plastic (for spyder 2 that is)

other than that you're correct, the filters drift over time
not only the properties of plastic change over time, also the electronics inside the meter change (capacitors)

Anyone interested...I have a DTP-94 for sale in the classifieds

RayJr

Thanks for the note Derek. Does Calman (with the D 2 LT) come with everything I need to calibrate? Or would I need extra test patterns etc? I have DVE.

Also, how does one best calibrate a projector for an HD satellite signal? Will Calman do this?

We provide free HTPC pattern generator if you are using a HTPC. Otherwise you will need a calibration DVD like DVE or many of the free and commercial DVD's available.

http://www.spectracal.com/sources.html

My immediate thought on this is a light box type arrangement with known filters might be possible & cheap.
Dichroic filters are the way to go here as the pass band can be controlled & they are pretty insensitive to drift over time due to the
way they generate the pass band (ie interference)

Edmunds optical has narrow bandpass dichroics for ~$40 to $80 ea, depending on the size of filter.
The specs for these filters are ±2nm for target wavelength & ~10-12nm FWHM bandpass:

"www.edmundoptics.com//onlinecatalog/displayproduct.cfm?productID=1903"

As you can see there is plenty of choice of wavelengths

I did a little more digging & found a couple of interesting articles that cover the use of these type of filters in this type of application.
This one uses similar filters in effectively the same way -

"ftp.fpdl.nist.gov/pub/DMATS/DMATS_02.pdf"

Interestingly there seems to be some impacts in the CIE coordinates at the extreme wavelengths (~400nm & 700nm). It may be better
to restrict the range to 450nm to 650nm.
This article discusses the errors seen in this calibration -

"ftp://ftp.fpdl.nist.gov/pub/DMATS/IntFilSID96.PDF"

I think something like a 12V halogen car bulb could be used as the source in a custom made box with appropriate diffuser, ND filter(s) & dichroic filters
& cost about $200 -$300.

It might not be NIST traceable, but it could be reasonable!

At the very least I think you would be able to see sensor changes. Comments...?

How would you know that it was a change in the sensor and not the lamp? Are you going to regulate the supply? What about the filters changing? If you get a difference, how do you know where it comes from? This is the whole point behind traceability...

So that people are aware, a NIST traceable light source has to be "recalibrated" itself every 50 hours of use, and most require a half-hour of warm-up to let the lamp's temperature stabilize. You need this stability and consistency of a known reference to test the variability that you see in off-the-shelf parts. Typically, the cheaper the part, the more variability in performance you see in the field. It is this variability that gets you with any of these filters, meters, etc.

Bill

Absolutely, I was not talking about a traceable source, I was thinking about something that might be good enough to provide a degree of confidence in a sensor vs assuming it was OK.

The questions are valid - Would a regulated halogen source have a stable enough spectral output to be considered constant? Are the filters stable?

I believe that dichroic filters are stable - they produce the band pass by using an interference layer that is sandwiched/sealed between two layer of clear glass. I've used these type of filters in signal detection for plasma processes without seeing degradation over multiple years of use.

As far as the light source goes, I think it would work, there seems to be a number of commercial sources that use this type of methodology. If luminosity is maintained over the bulb lifetime, does this mean that we don't see significant filament temp changes & hence the spectral output of the remains acceptably constant? I don't know.
Do you have any data on the magnitude of the change in the emission spectra that might be expected & how that would impact the CIE coordinates, all other things being equal?

Cheers, John

Short of doing sampling, at a minimum, of the inbound components, you ARE making this assumption. Even with sampling, you are making an assumption, as well, that your sample is, in fact, representative of the products you are receiving. Ideally, a DIYer would test each of the filters he or she planned to use, since you aren't heading for large-scale manufacturing, or you would use equipment from a "known good" source where someone else has done enough testing to verify the quality of the products. Averages are entertaining here, but standard deviations (and standard error) are where the rubber meets the road.


Filter stability is a different issue. When people talk about the stability of a filter, it is about a decay/degradation over time for an individual unit, not variance across units. As for a halogen lamp, it is probably "good enough" for DIY use if you had the ability to measure it at that given instant with a high quality meter. You absolutely cannot trust one over time (e.g., read it today, come back a month later, then use it as a reference without re-measuring).


Dichroic filters are good because of a number of factors. However, good ones tend to be expensive, thus violating the "cheap" ideal.


Which it isn't, as most any projector owner can attest.


No. The spectral output of a lamp will change over time.


For lamps in my house? No. For the lamps in some of the projectors I have owned? I did at one point, but I did not keep the data when the projectors went to new homes. My current projector, Sony VW60, I've been meaning to some longitudinal studies on, but have not had time to do the basic, background measurements. I've been looking into adding a stable, NIST-traceable light source to my lab, but we will probably put one up in Seattle, first, rather than with me.

Bill

Well, I just recently purchased an Eye-One Display LT off of Amazon and was calibrating my Samsung 58A550, which is said to have extremely accurate primaries and secondaries OOTB in Movie mode. I'm starting to wonder how accurate this colorimeter is, as I had to make significant changes to the primary and secondaries to get Delta E's under 5 on all the primaries (using the default settings they were all north of 15). However, I'm starting to think the yellows are too green and saturation is too muted now. Is it possible my Eye-One is simply way out of spec? Is there a way to get these things calibrated?

Tx

Just as with most things, you can get duds that slipped through QA. That being said, I have seen a lot of people claim accuracy without any backing detail, so while you may have an issue with the meter, I wouldn't necessarily blame the meter if your TV measured with a visible color error.

Actually, the TV, at default, measured as follows:



After calibrating the primary and secondary colors according to what the meter was telling me, the CIE was as follows:




All primaries and secondaries much much closer to reference per the Eye-One. However, it was clearly innaccurate. Yellows were more of a florescent green, greens glowed, and everything was very much undersaturated. So either the meter is off, or I've done something wrong (first time with a TV that I could calibrate colors so have never done that before).

pbc, what do your brightness values look like? And I assume when you say yellows look "greenish", you're referring to the yellow window pattern? It may very well be that your colorimeter is not working properly - did you buy it new?

Also, what calibration dvd are you using?

Finally, you may want to post your chc file in the HCFR calibration file thread so folks can take a look.

cheers,


--tom

Hi Tom,

Yes, I bought the meter new. I noticed the greenish yellow in actual programming. When others tried my settings on their Samsung sets they noticed the same thing.

I'll post in the HCFR thread ...

Thanks!

How does the i1-Pro compare against dedicated light meters when measuring luminance such as the CA813 or even more expensive calibrating tools, specially at the low end of grayscale and for contrast measures?

At low stimulus levels the AEMC 813 is much more accurate than an i1Pro...

"At low stimulus levels the AEMC 813 is much more accurate than an i1Pro"

Does this mean that my greyscale will be "better" with the AEMC813? I'd like to think that this purchase wasn't a waste. A few months back, I inquired if a colorimeter alone would be adequate (I forget which thread) and was informed by knowledgeable calibrators that I really needed both. I tripped across the Breyscale for Dummies thread a day after I ordered one. I will be using it and the iOne LT with a Vision HDP and an RS-1 FP as well as a JVC 65S998 RP.

Kevin

I don't have any experience using these meters, but I believe they are only of use for adjusting gamma and measuring contrast, not adjusting greyscale.

Please let us know how your AEMC813 ft-lamberts measurement compares to that of your colorimeter when used with your FP. That might be one measurement that it would be worth having the extra meter just to know that you really are at 12 ft-lamberts (at least within 3%). I haven't seen any comparisons like this, especially using HCFR.

Sorry To jump in, I was wondering if any one know's or has used the new spyder 3 (elite) and how it compares in accuracy to the older spyder 2 tv pro or even the iOne. I would be using it mainly for calibrating A CRT front projector, The specs of the new spyder 3 colorimeter sound much improved over the older spyder 2 so it may perform better in the lower IRE. Any help would be greatly Appreaciated....
Tom H ? or any one???

In addition to Derik's important storage method I cook'em too .

FWIW I "bake" ( 90f for 4 hours) my 3 tri-stimulus probes about every six months in a 14" x 14" top vented cardboard box using an 40 watt lamp as the heat source. I can adjust the box's temp so it's stable at 90 degrees before putting the probes in by opening or closing the vents. I use an two piece RF digital thermometer placing the sensor inside the box at the bottom, then I adjust the box's vents to the exact temp.
Cooking seems to have kept my two DTP-94's and my Millory Colorfacts C4 ? moisture free and stabilized very well over the past 5 years. At least in my mind and confirmed by my pre and post probe baking test measurments.
I sent the C4 in for factory cal about two years ago and it reads the same today. I believe from proper storage and baking.

BUMP Any one ???

From what i heard it's better in the low ire's

Thank's for the comment. I ended up going with the I-1pro spectrophotometer/CalMan software bundle..
Could some one Please comment on how well the EYE-ONE pro/With CalMan, performs in the low 0/10/20IRE readings taken off the screen with Highend CRT projectors. I did notice in the meter shoot out chart's that readings where taken from 30IRE....
Thank's

Once you get below 10cd/m² with an i1Pro, the readings become considerably slower in CalMAN due to their low-light handling technique. It seems to produce accurate results though, and they claim it's accurate down to 0.05cd/m² using this technique if I remember correctly. Whether that's at 10 IRE, 20 IRE, 30 IRE etc depends on the display and how it's set up though.

The newer Spyder3 may be improved over the last ones, but it's my understanding that they don't have very strict tolerances so unit-to-unit variation can be quite large. You may luck out and get a good one, but you wouldn't know unless you had a reference meter to compare it with.

Even though they are supposed to have improved low-light readings considerably over the Spyder2, most people consider the DTP-94, EyeOne Display 2 or Chroma5 to be better colorimeters.

If you don't have another meter to train the Chroma5, I would recommend either a DTP-94 (which I use) or an EyeOne Display 2.

Certainly, I've found my DTP-94 to track much closer to my i1Pro than the Chroma5 before it's profiled. I don't have any experience with the Display2 though.

Both the Display2 and DTP-94 have drawbacks. The DTP-94 needs you to take a black reading every ten minutes to maintain accuracy. The Display2 seems to be quite susceptible to temperature drifts and people seem to have issues using them with Plasmas in particular.

Hi tom,

I received my xrite I1pro today, and I'll be using it with colorfacts6.

Have you(or somebody else) ever experienced problems with taking dark readings?. because I have.

Sometimes, not all the time, colorfacts states that it cannot save the dark reading data. And when this happens the meter cannot be used.

It connects without problems.

Any advice would be greatly appreciated.

Dimitri

EDIT: The problem hasn't occurred anymore.

I was surprised how little difference there was on plasma, compared to my spyder2. But with LCD there is a BIG difference. About a ^10 for a 30 IRE window.

I know this is an old post. I'm trying to read through them all to learn as much as I can. I'm new here and just ordered an i1 Display 2 with Calman v3.2. How do I load this file from Derek ("Plasma.cdf" sample file of his plasma) to look at it. I've tryed but it keeps saying it will overwrite it? Obviously I'm not loading it in the right spot?
Thanks,

Edit: I just figured it out.... I'm so new to this software....

Hey guys,

Can anybody tell me if the x rite I1pro is technicly the same as the gretag I1pro?.

Or is there a quality/accuracy difference between the two?.

Regards,

Dimitri

X-rite bought Gretag a bit ago. All i1 Professionals start life in Switzerland, no matter whose label is on the outside.

Bill