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post #151 of 5750 Old 01-16-2010, 02:23 AM
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Quote:
Originally Posted by coderguy View Post

Any recommendations?

I've got a feeling that Chroma5 is going to be the answer

TomHuffman: what about a relatively old Chroma5? Would it benefit from being profiled against an i1Pro? Do the i1Pros stay accurate for longer, being spectrophotometers rather than tristimulus colorimeters?

THE LOUDNESS WAR IS OVER! - if you want it.


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post #152 of 5750 Old 01-16-2010, 04:52 AM
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Hi,

This is commenting on some earlier posts about what is the correct Gamma curve. (Please note this is a little GEEKY).

Last years I did some work with the BBC* here in the United Kingdom and they have been doing continuous evaluation of Gamma over four decades or more. The more recent results suggest that the "ideal" gamma for a TV display should be 2.35.

However the same research done by Japan's NHK** suggests 2.4 is closer.

I queried the BBC about this and it appears that the results are almost identical but that the BBC decides to recommend a rounding down to 2.35 and NHK decided to recommend a rounding up to 2.4.

The BBC recommendation is now part of the EBU's (Europe's answer to SMPTE) recommendation in their document Tech 3321- EBU HDTV Receiver Requirements.

Appendix A of this document explains in geeky details why this has changed form the traditional gamma of 2.2. It can be downloaded from the EBU technical website. As I have not posted before, I am not allowed to attach the web address but PM me if you cannot find it.

Further discussion with the BBC confirmed that they would be happy with a gamma of 2.35-2.4 as being"correct".

I do not have access to SMPTE recommendations but I do know that there is a liaison committee between the EBU and SMPTE regarding display specification and that the plan was to ensure that work was not duplicated.


*British Broadcasting Corporation ** Japan's Public Service broadcaster

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post #153 of 5750 Old 01-16-2010, 06:45 AM
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Quote:
Originally Posted by TomHuffman View Post

You don't need a license to use a reference device. Just enter the xy data manually.

So, in the specific case of an i1p you can read it in ChromaPure without a license or do you mean get the coordinates using another product e.g. CHCFR?


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post #154 of 5750 Old 01-16-2010, 06:47 AM
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Quote:
Originally Posted by TomHuffman View Post

Sounds reasonable. We'll add it to our roadmap.

Is your roadmap public or do you have an expected time for CM support?


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post #155 of 5750 Old 01-16-2010, 09:41 AM
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Quote:
Originally Posted by bodosom View Post

So, in the specific case of an i1p you can read it in ChromaPure without a license or do you mean get the coordinates using another product e.g. CHCFR?

One has to use another product (such as ColorHCFR) and manually enter the data into ChromaPure unless the unit is licensed in ChromaPure.

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post #156 of 5750 Old 01-16-2010, 03:37 PM
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Quote:
Originally Posted by bodosom View Post

Is your roadmap public or do you have an expected time for CM support?

Gosh, I can't be specific--not because I am being coy, but because I really don't know. We don't even have the SDK from X-Rite at this point. It will take a while.

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post #157 of 5750 Old 01-16-2010, 03:39 PM
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Quote:
Originally Posted by ev666il View Post

I've got a feeling that Chroma5 is going to be the answer

TomHuffman: what about a relatively old Chroma5? Would it benefit from being profiled against an i1Pro? Do the i1Pros stay accurate for longer, being spectrophotometers rather than tristimulus colorimeters?

It might for the reason you suggest, but we will be releasing something in the next few weeks that will address this issue.

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post #158 of 5750 Old 01-16-2010, 03:58 PM
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Quote:
Originally Posted by chienmort View Post

This is commenting on some earlier posts about what is the correct Gamma curve. (Please note this is a little GEEKY).

Last years I did some work with the BBC* here in the United Kingdom and they have been doing continuous evaluation of Gamma over four decades or more. The more recent results suggest that the "ideal" gamma for a TV display should be 2.35.

However the same research done by Japan's NHK** suggests 2.4 is closer.

I queried the BBC about this and it appears that the results are almost identical but that the BBC decides to recommend a rounding down to 2.35 and NHK decided to recommend a rounding up to 2.4.

The BBC recommendation is now part of the EBU's (Europe's answer to SMPTE) recommendation in their document Tech 3321- EBU HDTV Receiver Requirements.

Appendix A of this document explains in geeky details why this has changed form the traditional gamma of 2.2. It can be downloaded from the EBU technical website. As I have not posted before, I am not allowed to attach the web address but PM me if you cannot find it.

Further discussion with the BBC confirmed that they would be happy with a gamma of 2.35-2.4 as being"correct".

I do not have access to SMPTE recommendations but I do know that there is a liaison committee between the EBU and SMPTE regarding display specification and that the plan was to ensure that work was not duplicated.

Here's the document you refer to.

http://www.ebu.ch/CMSimages/en/tec_d...tcm6-54131.pdf

I see no mention of "why this has changed form the traditional gamma of 2.2." In fact, to my knowledge EBU has never supported 2.2. That's a standard from SMPTE 170M.

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post #159 of 5750 Old 01-16-2010, 04:13 PM
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Quote:
Originally Posted by TomHuffman View Post

You don't need a license to use a reference device. Just enter the xy data manually. It takes about a minute. I do it all the time, because we haven't gotten around to adding support for our reference spectro yet.

I don't get it. How do I get the xy data for the reference meter if I don't have a license for it ? Are you suggesting using HCFR (or other software) to get the reference data ?

Quote:
Also, using the i1Pro as a reference to correct a Chroma 5 would not be a good idea. The Chroma 5, especially a relatively new one, offers nearly the same accuracy as an i1Pro.

Then why would someone purchase the i1 Pro/Display 2 combo over the Chroma 5 package ?

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post #160 of 5750 Old 01-16-2010, 06:16 PM
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Quote:
Originally Posted by stash64 View Post

I don't get it. How do I get the xy data for the reference meter if I don't have a license for it ? Are you suggesting using HCFR (or other software) to get the reference data ?

Exactly.
Quote:
Originally Posted by stash64 View Post

Then why would someone purchase the i1 Pro/Display 2 combo over the Chroma 5 package ?

The i1Pro has some advantages. It is less susceptible to degradation over time and it is largely unaffected by different display technologies.

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post #161 of 5750 Old 01-16-2010, 07:50 PM
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Thanks Tom. I feel closer to a purchase decision now. I think the Chroma5 package makes the most sense for me and my plasma and my only remaining issue would be maintenance of the meter. Does X-Rite have any maintenance/storage tips for the Chroma5 ? (I don't recall ever seeing any Chroma5 data on the X-Rite website). Also wondering if X-Rite or ChromaPure has any type of calibration or re-certification program or service for the Chroma 5 ? If not, is this a future possibility ?

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post #162 of 5750 Old 01-16-2010, 08:09 PM
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Quote:
Originally Posted by stash64 View Post

Also wondering if X-Rite or ChromaPure has any type of calibration or re-certification program or service for the Chroma 5 ? If not, is this a future possibility ?

Definitely. Coming very soon.

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post #163 of 5750 Old 01-16-2010, 08:41 PM
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Quote:
Originally Posted by TomHuffman View Post

Definitely. Coming very soon.

Very good. Even closer now !!!

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post #164 of 5750 Old 01-16-2010, 08:59 PM
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Quote:
Originally Posted by ev666il View Post

I've got a feeling that Chroma5 is going to be the answer

I was actually asking more about HW options, as I can deal with the software later. Guess I will start a new thread on this.



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post #165 of 5750 Old 01-16-2010, 09:05 PM
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Quote:
Originally Posted by coderguy View Post

I was actually asking more about HW options, as I can deal with the software later. Guess I will start a new thread on this.

The X-Rite Display 2 LT. It's about $129.

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post #166 of 5750 Old 01-16-2010, 09:19 PM
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Tom, speaking of the cost of the Display2 LT, would you not recommend getting a new DTP-94 instead? I have no empirical evidence but everything I hear is that the DTP-94 is superior in every way. Coloreyes sells brand new bare DTP-94's for $150 at this link. If what I read about the DTP-94 is true, the extra $25 sounds like a no brainer.
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post #167 of 5750 Old 01-16-2010, 09:28 PM
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To add to what SiegeX asked, do these devices generally work with front projectors without buying extra stuff.

Such as:
Do I need to buy anything special with it to specifically work with a projector?

Also, do I need a tripod (or can I use a black table or just stack boxes and place it on that)?



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post #168 of 5750 Old 01-17-2010, 02:37 AM
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Quote:
Originally Posted by coderguy View Post

I was actually asking more about HW options, as I can deal with the software later.

The Chroma5 is a piece of hardware (not to be confused with Tom's ChromaPure software).

THE LOUDNESS WAR IS OVER! - if you want it.


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post #169 of 5750 Old 01-17-2010, 07:45 AM
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The most important thing about getting inexpensive hardware is buying from someone who can provide assurance that it's new and will help you out if it goes south. I have two inexpensive meters: a D2 and -94. The D2 was old* and is unstable. The -94 came from IC and has poor correspondence with my C5 so I don't use it even though it's faster at low stimulus.

*If your software can report the calibration date it's so very useful.


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post #170 of 5750 Old 01-17-2010, 08:15 AM
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I have no experience with either the Display2 LT or the DTP-94 but colorimeters are not known for long term stability....evidently as they age their filters change and as such accuracy degrades. Keeping that in mind here is a quote from Derek in another thread (the thread is titled Calibration Issues):

Quote:
Originally Posted by derekjsmith View Post

Well I would believe X-Rite since I asked them last week where these guys are getting the DTP-94's. X-Rite went back a looked at the sales records and said they have not built any for two years and the last order shipped was over two years ago but it was a very large order.

If true then these units are already 2 years old FWIW.

Per Tom, they are working on a calibration or re-certification program for the Chroma 5 which should keep it viable for years to come. I don't know if this will include the Display2 LT or the DTP-94 so perhaps Tom can clarify. If not, more money now may very well mean less money later by not having to replace an inaccurate meter due to aging.

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post #171 of 5750 Old 01-17-2010, 07:32 PM
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Quote:
Originally Posted by TomHuffman View Post

Here's the document you refer to.

http://www.ebu.ch/CMSimages/en/tec_d...tcm6-54131.pdf

I see no mention of "why this has changed form the traditional gamma of 2.2." In fact, to my knowledge EBU has never supported 2.2. That's a standard from SMPTE 170M.

Started to watch a BBC Blu-ray - Nature's Most Amazing Events. On it was a Setup Test for your system. I have a Nov build LG 55LH90 and have calibrated it with a Chroma5 and the Picture Wizard. Brightness was best set at 58, Contrast at 84 and Colour at 47. On the British test the Colour at 47 was OK, but to pass the Brightness and Contrast, Brightness ended up at 71 and the Contrast at 100. These settings looked better on my set. So for there being such a difference, then I assume the Brits are using a somewhat different standard?

After viewing the DVD then returning to the normal world it became obvious, these settings work on the BBC material but too bright and somewhat washed out on standard viewing materials.
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post #172 of 5750 Old 01-18-2010, 02:27 AM
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Tom Said


I see no mention of "why this has changed form the traditional gamma of 2.2." In fact, to my knowledge EBU has never supported 2.2. That's a standard from SMPTE 170M.
__________________

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As I understand it, the original work that was done to determine Gamma was from the EMI/Marconi work done in the 1930s. This was done prior to the start of British TV transmission in 1936. However there was an intermittent but ongoing process at the the BBC to revisited all their own previous research. In addition a number of new and older CRTs were re-measured using modern instruments. This was the basis of the new recommendations.

I will ask my contacts why they think the difference between 2.2 and 2.35 occurred.

With the NHK research, I was only told this in passing and I should perhaps have put that in quotation marks. I will try (I don't read Kanji so this may be a long process) to find out their reasons and methodology.

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post #173 of 5750 Old 01-18-2010, 01:11 PM
 
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Quote:
Originally Posted by chienmort View Post

Tom Said


I see no mention of "why this has changed form the traditional gamma of 2.2." In fact, to my knowledge EBU has never supported 2.2. That's a standard from SMPTE 170M.
__________________

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As I understand it, the original work that was done to determine Gamma was from the EMI/Marconi work done in the 1930s. This was done prior to the start of British TV transmission in 1936. However there was an intermittent but ongoing process at the the BBC to revisited all their own previous research. In addition a number of new and older CRTs were re-measured using modern instruments. This was the basis of the new recommendations.

I will ask my contacts why they think the difference between 2.2 and 2.35 occurred.

With the NHK research, I was only told this in passing and I should perhaps have put that in quotation marks. I will try (I don't read Kanji so this may be a long process) to find out their reasons and methodology.

I've never seen any evidence of the 2.2 coming from anywhere except a relatively recent misreading of the 1953 NTSC gamma standard which had the encode gamma often expressed as 1/2.2. This is doubly mistaken because it's misreading the standard and ignoring the history of rendering intent and the desire for an end-to-end greater than 1.0 by assuming that the inverse of the encode is what the decode should be, in addition to the fact that if this is where it's coming from (it seems that way to me) that it's drawn from an outdated and irrelevant gamma standard that has been superseded by Rec709.

The other place that it seems to come from is from a misreading of Rec709, and that seems to be where the 2.22 figures come from. Rec709 cites an exponent of .45 for the encode gamma, but that's only for part of the whole function, and doesn't characterize the function properly which is closer to about ~.5 because of the linear tail, or more precisely about .51. But if you take only the non-linear portion of Rec709 encode gamma standard of .45 and inverse that (again wrongly assuming that the inverse of the encode should be what the decode is) then you get to 2.2222.... And this is again a two-step misreading of the standard because Rec709 isn't accurately characterized as having an encode gamma of .45 because that ignores the linear portion of the transfer function, and it continues to assume wrongly that the decode gamma should just be the inverse of the encode gamma. If the end-to-end gamma is 1.0, that returns the accurate scene tristimulus values (if unaltered elsewhere, which is generally happening anyway so accuracy to the scene isn't really an achievable goal usually anyway), but it doesn't yield good perceptual accuracy.
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post #174 of 5750 Old 01-18-2010, 02:02 PM
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Quote:
Originally Posted by ChrisWiggles View Post

I've never seen any evidence of the 2.2 coming from anywhere except a relatively recent misreading of the 1953 NTSC gamma standard which had the encode gamma often expressed as 1/2.2. This is doubly mistaken because it's misreading the standard and ignoring the history of rendering intent and the desire for an end-to-end greater than 1.0 by assuming that the inverse of the encode is what the decode should be, in addition to the fact that if this is where it's coming from (it seems that way to me) that it's drawn from an outdated and irrelevant gamma standard that has been superseded by Rec709.

The other place that it seems to come from is from a misreading of Rec709, and that seems to be where the 2.22 figures come from. Rec709 cites an exponent of .45 for the encode gamma, but that's only for part of the whole function, and doesn't characterize the function properly which is closer to about ~.5 because of the linear tail, or more precisely about .51. But if you take only the non-linear portion of Rec709 encode gamma standard of .45 and inverse that (again wrongly assuming that the inverse of the encode should be what the decode is) then you get to 2.2222.... And this is again a two-step misreading of the standard because Rec709 isn't accurately characterized as having an encode gamma of .45 because that ignores the linear portion of the transfer function, and it continues to assume wrongly that the decode gamma should just be the inverse of the encode gamma. If the end-to-end gamma is 1.0, that returns the accurate scene tristimulus values (if unaltered elsewhere, which is generally happening anyway so accuracy to the scene isn't really an achievable goal usually anyway), but it doesn't yield good perceptual accuracy.

You know what does look really good though (if you've got a LUT so you can calibrate to it) is if you calculate the rec.709 xfer function first so you get an end to end gamma of 1.0 and then apply the power function as the result so you get an end to end gamma of 1.1-1.2, I find 1.15-1.2 can look REALLY good. It's a very sRGBish kind of curve.

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post #175 of 5750 Old 01-18-2010, 04:05 PM
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I would like to apologise to Tom for contaminating this forum. I did not intend to become a gamma bore.

I will not waste anymore time with this until I have the reports that I reffered to.

Deaddog
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post #176 of 5750 Old 01-18-2010, 04:41 PM
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"Quote:
Originally Posted by stash64
Then why would someone purchase the i1 Pro/Display 2 combo over the Chroma 5 package ?

The i1Pro has some advantages. It is less susceptible to degradation over time and it is largely unaffected by different display technologies."
__________________
Tom Huffman

Tom, can we say that the best combination is the i1Pro with one of the cheap colorimeters like the Display 2? Of course, I know it would be better to have the i1Pro with the Chroma 5 but it is too expensive.
I have done a test with the Spyder3 with calman and then I measured the result with the i1Pro and Colorfacts. The Spyder3 is supposed to come calibrated to be used with Calman but the calibration obtained with that combo is very different to the calibration obtained using the i1Pro. I recheck the calibration with the i1Pro using HCFR and Chromapure with similar results: the Spyder3 Calman combo is too green.
Question: the calibration in the Chroma 5 is a profile in the program or it is a program inside the Chroma 5? Do I need to use the i1Pro to do a Meter Offset for the Chroma 5?

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post #177 of 5750 Old 01-18-2010, 06:40 PM
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Quote:
Originally Posted by Federico View Post

Tom, can we say that the best combination is the i1Pro with one of the cheap colorimeters like the Display 2? Of course, I know it would be better to have the i1Pro with the Chroma 5 but it is too expensive.

Actually, as I have said before, the Chroma 5 will provide accuracy similar to an i1Pro, at least initially, so pairing an i1Pro with a Display 2 would more sense.

Quote:
Originally Posted by Federico View Post

Question: the calibration in the Chroma 5 is a profile in the program or it is a program inside the Chroma 5? Do I need to use the i1Pro to do a Meter Offset for the Chroma 5?

Currently, the only calibration tables are in the firmware of the Chroma 5 itself.

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
Springfield, MO

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post #178 of 5750 Old 01-18-2010, 06:43 PM
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Quote:
Originally Posted by TomHuffman View Post

Currently, the only calibration tables are in the firmware of the Chroma 5 itself.

Can these tables be updated (if necessary) when the unit is re-certified?

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post #179 of 5750 Old 01-18-2010, 07:42 PM
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Quote:
Originally Posted by Geof View Post

Can these tables be updated (if necessary) when the unit is re-certified?

That would (will) be done at the software level, along with some other goodies we haven't finished yet.

-TH

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
Springfield, MO

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post #180 of 5750 Old 01-30-2010, 05:59 PM
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I'm a new user of Chromapure. I must say that this soft rock and is very easy to use. I was able to calibrate my RS20 to perfection with this thing. I have the i1pro/display 2 LT combo. The video on the website are very good to start you and Tom is very helpfull and fast to answer questions. I have no problem recommended it.


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