spyder2 lcd filter function - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 27 Old 02-12-2007, 09:10 AM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
I was curious about the effect of the removable filter on the spyder2 so I measured it's transmission using a small spectrograph and a 75% gray target as reference. The results are in the attached pdf. It appears the filter is used to create the red edge of the photopic response function. I also plotted spectra(uncalibrated) from my plasma display and my laptop display. There is significant energy in the roll-off portion of the filter which indicates to me that removing the filter will give erroneous results for these displays meaning you should not use CRT mode for plasmas. Thoughts?


-scott

 

s2filter.pdf 19.7939453125k . file
zoyd is online now  
Sponsored Links
Advertisement
 
post #2 of 27 Old 02-12-2007, 09:24 AM
AVS Special Member
 
derekjsmith's Avatar
 
Join Date: Oct 2003
Location: Mukilteo, WA
Posts: 1,890
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 98
Yes it is an IR filter and Plamas have plenty of IR. So without the filter the S2 would see way more Red than the human eye does.

Derek

CTO / Founder - SpectraCal Inc.
derekjsmith is offline  
post #3 of 27 Old 02-12-2007, 09:38 AM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
In addition to being an IR filter, you can see that it also has significant reduction of energy in the red, basically anything above 610 nm, and even effects the transmission down to 560nm. Since plasmas use similar phosphors that CRT's do I originally thought the CRT mode would be the better choice. However, it appears that CRT mode is useless for any display because removing the filter will change the overall color response of the sensor above 560 nm, thereby destroying it's calibration.


-scott
zoyd is online now  
post #4 of 27 Old 02-12-2007, 09:44 AM
AVS Special Member
 
derekjsmith's Avatar
 
Join Date: Oct 2003
Location: Mukilteo, WA
Posts: 1,890
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 98
The S2 has two internal calibration tables that are selected with the CRT mode and all others. As many of the tristim meters on the market do. So in theory it should without the IR filter work on a CRT just fine. The problem with the S2 is they don't seem to be factory calibrated very well with or without the IR filter. So if you have a few of them you will get a different result from each but which one is right.

Derek

CTO / Founder - SpectraCal Inc.
derekjsmith is offline  
post #5 of 27 Old 02-12-2007, 09:53 AM
Senior Member
 
Aaron S's Avatar
 
Join Date: May 2002
Location: Merrimack , NH , USA
Posts: 298
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I had run some measurements with the SpyderTV sensor on a Pioneer plasma in LCD vs CRT mode w/o filter. The link has the HCFR files if you're interested.

http://www.avsforum.com/avs-vb/showt...&&#post9551257
Aaron S is offline  
post #6 of 27 Old 02-12-2007, 10:02 AM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by derekjsmith View Post

The S2 has two internal calibration tables that are selected with the CRT mode and all others. As many of the tristim meters on the market do. So in theory it should without the IR filter work on a CRT just fine.

I don't think it is possible to calibrate the sensor for two different filter functions. As I understand it a filter based colorimeter must mimic the functional shape of the human eye response because the sensor integrates this function across the source. Since the external filter on the s2 changes the filter response it can no longer mimic the eye response (if it did with the filter in place). Spectrometer based sensors like the i1 don't have this problem because they can perform the integral on measured spectra directly.
zoyd is online now  
post #7 of 27 Old 02-12-2007, 10:04 AM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by Aaron S View Post

I had run some measurements with the SpyderTV sensor on a Pioneer plasma in LCD vs CRT mode w/o filter. The link has the HCFR files if you're interested.

http://www.avsforum.com/avs-vb/showt...&&#post9551257

Thanks Aaron, I see the same behavior, way off in green with the filter, closer without the filter. After these tests I do not believe any of the s2 chromiticity numbers (it's still fine for gray scale calibrations)
zoyd is online now  
post #8 of 27 Old 02-12-2007, 10:17 AM
slb
AVS Special Member
 
slb's Avatar
 
Join Date: Sep 2002
Location: San Francisco North Bay
Posts: 1,483
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
How have tristimulus sensors handled IR and plasmas in the past? I know they were not very good for LCD displays unless calibrated specifically for them, but until recently, I do not remember ever seeing mention of an IR filter being required.
slb is online now  
post #9 of 27 Old 02-12-2007, 10:22 AM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by slb View Post

How have tristimulus sensors handled IR and plasmas in the past? I know they were not very good for LCD displays unless calibrated specifically for them, but until recently, I do not remember ever seeing mention of an IR filter being required.


I think a good tristimulus sensor is source independent, it's supposed to be a "standard observer" so the only requirement is that it's filter stack reproduces the standard observer response. That's why allowing for the choice between CRT and LCD doesn't make sense to me.
zoyd is online now  
post #10 of 27 Old 02-12-2007, 12:38 PM
Member
 
subraman's Avatar
 
Join Date: Jul 2002
Posts: 116
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by zoyd View Post

I think a good tristimulus sensor is source independent, it's supposed to be a "standard observer" so the only requirement is that it's filter stack reproduces the standard observer response. That's why allowing for the choice between CRT and LCD doesn't make sense to me.

It didn't make sense to me either, till I realized that inexpensive tristimulus meters work by a combination of filter design and calibration (fudging?). So, if the calibration is done with a CRT source, it will not work so well with an LCD and so on. Come to think of it, even the expensive ones are made the same way.
subraman is online now  
post #11 of 27 Old 02-12-2007, 12:50 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by subraman
It didn't make sense to me either, till I realized that inexpensive tristimulus meters work by a combination of filter design and calibration (fudging?). So, if the calibration is done with a CRT source, it will not work so well with an LCD and so on. Come to think of it, even the expensive ones are made the same way.
Yes, after reading a bit more on how these things are made, I've just come to the same realization and I think it's a big problem because there is no "standard" LCD, CRT, or Plasma spectral response. Yes, there are similarities but as the technology changes and new materials are used the spectral distribution is going to change and negate the sensor calibration. I found a good summary of the problem here:

 

R30_ACCURATE-CHROMATICITY-MSMT_6-06.pdf 166.119140625k . file
zoyd is online now  
post #12 of 27 Old 02-12-2007, 02:21 PM
AVS Special Member
 
derekjsmith's Avatar
 
Join Date: Oct 2003
Location: Mukilteo, WA
Posts: 1,890
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 98
This is why I think the S2 design is great. Because it has 7 sensors to better detect the spectral response over the ones that only have 3 or 4. It has a light pipe to minimized off angle light on a LCD, a removable IR filter for Plasma and a diffuser for ambient, all for under $100. Just wish they had a calibration service and NIST certs or allowed 3rd parties to setup such a service.

Derek

CTO / Founder - SpectraCal Inc.
derekjsmith is offline  
post #13 of 27 Old 02-12-2007, 02:49 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by derekjsmith View Post

This is why I think the S2 design is great. Because it has 7 sensors to better detect the spectral response over the ones that only have 3 or 4. It has a light pipe to minimized off angle light on a LCD, a removable IR filter for Plasma and a diffuser for ambient, all for under $100. Just wish they had a calibration service and NIST certs or allowed 3rd parties to setup such a service.


I agree that using 7 sensors allows you to minimize errors with respect to the standard observer functions better than 3 or 4, but that doesn't change the fact that the calibration is now source dependent, a serious drawback for anyone who does precision work. btw, do you know if the spyder2 people have published what their filter/sensor transmission functions look like?
zoyd is online now  
post #14 of 27 Old 02-12-2007, 04:46 PM
AVS Addicted Member
 
krasmuzik's Avatar
 
Join Date: Oct 1999
Location: NewPort, VA
Posts: 11,270
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
derek

I thought the LCD light pipe and IR filter are the same assembly - until you just posted this and I took a tiny screwdriver to pop it out the filter. It was not a new one I received and the filter had water spots on it. I presume the calibration table assumes both the pipe and filter are in place - as it is not really a modular assembly even though it does appear to come apart. The diffuser does not come off - at least I am not going to try to take it off.

zoyd search out the Spyder patent - the calibration process is more complex than you are making it out to be. A calibrated Spyder competes with the similar KM design with 5x more sensor that is sold as a cheap portable substitute for a spectroradiometer.

http://patft.uspto.gov/netacgi/nph-P...S=PN/6,163,377

Not sure what the patent office uses for images - my browser is not showing them - but the claims indicate the response curves are in there.

They use the calibration method in this paper - which I am too cheap to pay for...

http://www.iop.org/EJ/abstract/0022-3735/8/1/016

colorimeters are only as good as their filter set matching the CIE standard eye response - and calibration thereof.
krasmuzik is offline  
post #15 of 27 Old 02-12-2007, 05:12 PM
AVS Special Member
 
derekjsmith's Avatar
 
Join Date: Oct 2003
Location: Mukilteo, WA
Posts: 1,890
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 98
Quote:
Originally Posted by krasmuzik View Post

derek

I thought the LCD light pipe and IR filter are the same assembly - until you just posted this and I took a tiny screwdriver to pop it out the filter. It was not a new one I received and the filter had water spots on it. I presume the calibration table assumes both the pipe and filter are in place - as it is not really a modular assembly even though it does appear to come apart. The diffuser does not come off - at least I am not going to try to take it off.

They are, I was just experimenting with mine and removed the IR filter to run with my i1Pro to see what the IR cut is for the S2. So then I started to experiment with and without the IR filter in the light pipe. I'm just not happy unless I'm taking something apart

Derek

CTO / Founder - SpectraCal Inc.
derekjsmith is offline  
post #16 of 27 Old 02-12-2007, 05:15 PM
AVS Addicted Member
 
krasmuzik's Avatar
 
Join Date: Oct 1999
Location: NewPort, VA
Posts: 11,270
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Well at least now we know it was a plasma IR filter - I thought it was a polarizer for LCD light!
krasmuzik is offline  
post #17 of 27 Old 02-12-2007, 05:42 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by krasmuzik View Post

derek

zoyd search out the Spyder patent - the calibration process is more complex than you are making it out to be. A calibrated Spyder competes with the similar KM design with 5x more sensor that is sold as a cheap portable substitute for a spectroradiometer.

http://patft.uspto.gov/netacgi/nph-P...S=PN/6,163,377

Not sure what the patent office uses for images - my browser is not showing them - but the claims indicate the response curves are in there.

They use the calibration method in this paper - which I am too cheap to pay for...

http://www.iop.org/EJ/abstract/0022-3735/8/1/016

colorimeters are only as good as their filter set matching the CIE standard eye response - and calibration thereof.

Here is that image from the patent, it's not clear to me whether this includes the external filter or not, it looks like the most significant error on the long side of the red response. I have no doubt that if calibrated properly this type of sensor can have very good performance assuming that the display you use it for has the same spectral distribution as the one used to calibrate the s2, this will not be the case for those users trying to calibrate a plasma display.

edit: 2nd file attached shows the separate filter layer responses indicating that the CIE reproduction shown in figure one is formed from these 8 layers, I believe 7 of them are measured on separate detectors. So the external filter would add another layer and form the red end cut-off in the overall response. It seems to me that if you remove the external filter the response will be very far away from the CIE ideal.
LL
LL
zoyd is online now  
post #18 of 27 Old 02-12-2007, 06:55 PM
AVS Addicted Member
 
krasmuzik's Avatar
 
Join Date: Oct 1999
Location: NewPort, VA
Posts: 11,270
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
The point of their patent is to use edge rather than bandpass filters. This means their filter stack does not optically make a CIE XYZ response - rather they take the response of the edge filters - and do some DSP math to come up with the XYZ response. XYZ response is the integral of the spectral response under each of those CIE filter curves. In a traditional tristimulus sensor - you would get that from three perfectly CIE matched optical filters - which are hard to make to match CIE. The Spyder design (and the KM CS-200 design wiht 5x more filters) - you are taking the optical responses of multiple filters - applying DSP and calibration tables to come up with the XYZ response thru curve fitting of data.

So according to that diagram - filter 7 is good for >640nm, filter 6 is good for >600nm - take their integral difference and you know the energy in band 600-640 (roughly as it depends on each diode and filter performance) Above 640nm CIE has some X, little Y and no Z response - yet the Spyder filters pass all this spectra. This mean deep red/IR band is digitally filtered rather than optically - thus the external filter which optically converts all of the edge filters into essentially passband filters to avoid the digital noise of doing a rolloff.

The whole point of XYZ filters concept is that it can measure something that is not spectrally matched to your reference source and tell how they appear different to the eye - it is the integral response that matters. The error comes where the reference and actual curves maximally differ only if there is significant spectral energy for the source at those wavelengths such that the integral response is off.

They key in all this is do you get the same integral response when you apply the resultant filters - and that depends on the calibration tables in the Spyder - which Derek has investigated and found many samples all had the same tables. It is unlikely that individual diodes and filters have the same response - so the error lies in the poor factory preset - it needs calibrated to be accurate. They are going to charge way more for the Platinum sensor even though it is the same hardware - you pay for that calibration. It does not matter how good the sensor design is if it is not calibrated - just like your TV.

Keep in mind those patent charts are demonstrating an example - who is to say your sensor is over/under the IR part of the X curve - the point is - your sensor is different.
krasmuzik is offline  
post #19 of 27 Old 02-12-2007, 07:16 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by krasmuzik View Post

The point of their patent is to use edge rather than bandpass filters. This means their filter stack does not optically make a CIE XYZ response - rather they take the response of the edge filters - and do some DSP math to come up with the XYZ response. XYZ response is the total energy - the integral under those curves

So according to that diagram - filter 7 is good for >640nm, filter 6 is good for >600nm - take their integral difference and you know the energy in band 600-640 (roughly as it depends on each diode and filter performance) Above 640nm there is some X, little Y and no Z response. This mean deep red/IR band is digitally filtered rather than optically - thus the external filter which optically converts all of the edge filters into essentially passband filters to avoid the digital noise.

ok, thanks for that explanation, this makes alot of sense now. Simulating bandpass filters using edge filters allows you to optimize rising AND falling slopes of the X,Y,Z functions.

Quote:
Originally Posted by krasmuzik View Post

They key in all this is do you get the same integral response when you apply the resultant filters - and that depends on the calibration tables in the Spyder - which Derek has investigated and found many samples all had the same tables. It is unlikely that individual diodes and filters have the same response - so the error lies in the poor factory preset - it needs calibrated to be accurate. They are going to charge way more for the Platinum sensor even though it is the same hardware - you pay for that calibration.

That is precisely my point, you don't get the "same integral response" unless the source function (LCD, plasma, crt, whatever) is identical (spectrally) as what was used to calibrate. It doesn't matter how good the s2 calibration is if what you are calibrating has signifcantly different spectral features. For example, you could not use an S2 to calibrate a tungsten lamp unless they provide calibration coefficients obtained with that source.
zoyd is online now  
post #20 of 27 Old 02-12-2007, 07:28 PM
AVS Addicted Member
 
krasmuzik's Avatar
 
Join Date: Oct 1999
Location: NewPort, VA
Posts: 11,270
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
No you can indeed measure different spectra - that is the whole point of simulating standard eye response rather than a standard CRT response. The eye sees different spectra that have the same integral response as the same color. So only if the source spectra has significant energy where the XYZ curve approximation is large integral error would this be a problem.

Based on this patent example - certainly large IR spectra would not match very well because that edge is digitally created without the external filter to roll it off. And the peaks of the XYZ in this example have some error - but the source spectra would need to have its maximum energy at those wavelengths for this to show. Surely for this example lasers at 460, 560, 600 would have a lot of error - but you would read lasers at 470, 570, 620 without error. So the spikier the spectra - the greater possibility of error - but that does not guarantee error. The more broadband the spectra - the greater chance of these wavelength errors canceling out.

The KMCS200 has more on this in their datasheet. With more sensors you get a tighter curve fit - and they qualify it for all kinds of display types - yet this is a colorimeter- it is not a spectroradiometer. But since they have the tighter curve fit even the narrow band primaries will measure very well.

http://www.tequipment.net/pdf/Minolt..._datasheet.pdf
krasmuzik is offline  
post #21 of 27 Old 02-12-2007, 07:30 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by krasmuzik View Post

The error comes where the reference and actual curves maximally differ only if there is significant spectral energy for the source at those wavelengths such that the integral response is off.

yes, this is what I was trying to get at. For LCD's and Plasmas which have sharply peaked emission features errors in the source->filter integral can be amplified.

your laser example is indeed much better than my lamp example.
zoyd is online now  
post #22 of 27 Old 02-12-2007, 07:44 PM
AVS Addicted Member
 
krasmuzik's Avatar
 
Join Date: Oct 1999
Location: NewPort, VA
Posts: 11,270
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
But this is true even of spectroradiometers whose sampling rate is too low - and certainly true of colorimeters with even fewer filters that clearly had no money spent on finding three optically perfect X, Y, Z filters (if they even exist)! Factor in nonlinear optielectronic response as far as working at low light levels...

The Spyder flaws are not one of design - they are ones of default factory calibration.
krasmuzik is offline  
post #23 of 27 Old 02-12-2007, 07:56 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Thanks for the feedback, I have a much better appreciation of the design concept behind the s2 now and agree that it is impressive. I wish that they came with better factory cals but I plan on cross-calibrating mine against a reference spectrograph to take care of that.
zoyd is online now  
post #24 of 27 Old 02-12-2007, 08:04 PM
AVS Addicted Member
 
krasmuzik's Avatar
 
Join Date: Oct 1999
Location: NewPort, VA
Posts: 11,270
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Well - you cannot have mine - for the lamp I tested it on it fought the KM instrument to the ten-thousandth place - which is good enough for FPTV. And when I reviewed the Ruby I got same xy primaries from a PR650 based review. Hopefully Spyder Platinum solves the calibration - the patent points out that their technique allows the sensor to be manufactured cheaply (diodes, filters, plastic) - the cost is in calibrating it - especially if you want traceability. Not something you will find in the fleabay $99 special. People should now understand why calibrated sensors are expensive - especially if you want to measure dark narrow band primaries.

The cross sensor corrections you get in the software is not going to be good as calibrated XYZ curve generation in the firmware - for the same reasons you mentioned - it will be good for the similar lamp and brightness.
krasmuzik is offline  
post #25 of 27 Old 02-12-2007, 08:21 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
It seems the s2 has found a good breakpoint between the cheapies (3-4 broadband filters) and the big hitters like the KM with 40 channels. Like you say though, there is no way to skimp on calibration.
zoyd is online now  
post #26 of 27 Old 05-01-2007, 03:32 PM
AVS Special Member
 
Mark Hunter's Avatar
 
Join Date: Feb 2000
Location: New Jersey
Posts: 4,870
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 10
Wow, this is a great discussion.

Zoyd wrote:
Quote:


I don't think it is possible to calibrate the sensor for two different filter functions.

You can really think of it as TWO sensors. There are TWO separate coefficient tables, and one is used with the filter ON, and one is used with the filter OFF. They are BOTH designed to match CIE standard observer curves...it's just that the filter reduces IR emissions and off-axis light, and with the filter removed, we get more light transmission to the detectors.

If you're really curious about how all of this works, check out the calibration FAQ:
http://www.spydertvpro.com/faqs2.php

Mark Hunter
Technical Director, Home Theater Products
Datacolor, Inc.
Mark Hunter is offline  
post #27 of 27 Old 05-01-2007, 05:56 PM - Thread Starter
AVS Special Member
 
zoyd's Avatar
 
Join Date: Sep 2006
Location: Planet Dog
Posts: 4,427
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Liked: 299
Quote:
Originally Posted by Mark Hunter View Post

Wow, this is a great discussion.

Zoyd wrote:


You can really think of it as TWO sensors. There are TWO separate coefficient tables, and one is used with the filter ON, and one is used with the filter OFF. They are BOTH designed to match CIE standard observer curves...it's just that the filter reduces IR emissions and off-axis light, and with the filter removed, we get more light transmission to the detectors.

If you're really curious about how all of this works, check out the calibration FAQ:
http://www.spydertvpro.com/faqs2.php

Hi Mark,

yeah, this discussion was early on in my "education" about the calibration of photopic devices (I'm more familiar with absolute radiometry). I like the spyder design, have you guys done any tests on plasmas and thought about providing separate calibration tables for them. We have done a lot of probe comparison work recently between the S2, D2, DTP-94 and i1pro on plasmas, check out this thread.
zoyd is online now  
Reply Display Calibration

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off