Video Calibration Q&A - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 77 Old 12-15-07, 12:00 PM Thread Starter
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Video Calibration Q&A

I thought that I might open up a calibration Q&A thread for people considering calibrating their video chains. Fair warning: I do sell software that does this, but our forum is the place for tech support for our product. I also don't do tech support on specific models. Sorry, but I have not "seen them all". Far from it, actually. What I can answer are questions on meters, techniques and theory/practice on some key aspects of video calibration that seem to trip people up.

Bill

CalMAN -- Home Theater Calibration Software
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post #2 of 77 Old 12-15-07, 08:38 PM
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Re: Video Calibration Q&A

Thanks Bill... we appreciate your knowledge.
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post #3 of 77 Old 12-16-07, 10:10 AM
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Re: Video Calibration Q&A

That would be GREAT! Just refer the hardware specific questions to the Manufacturer Service and Support Forum and I will see what I can come up with for help from that perspective. We will try to keep the discussion focused on general questions about calibration, not support for your product nor for specific hardware.

I have some reference links at

http://www.hometheatershack.com/foru...html#post43531

that you might want to review and suggest changes to. Your expertise and willingness to share your experience is much appreciated.




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post #4 of 77 Old 01-18-08, 11:51 PM
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Re: Video Calibration Q&A

I for one, greatly appreciate a general QA thread about calibration.

Over the past week, I borrowed a colorimeter from a local graphics shop and did a newbish effort at calibrating my display. I managed to get my grayscale rather accurate, but despite the picture looking much better than uncalibrated, there was a lot left to be desired.

So i'm going to do a factory reset and proceed with starting over.

Questions:

1) What is the first thing that should be adjusted. Contrast level to ~35fL for a plasma, then brightness?

2) Should ALL user controls be centered to 0 in order to set the above values in a service menu? (Contrast and Sub-Brightness)

3) Is the "smart method" as I've heard it mentioned the best way to do brightness? i.e. Dropping red/blue bias/cut/offset/etc and only adjusting the green value, then bringing red/blue back up to proper levels? (similarly, using red gain as your 'max' level and adjusting green/blue on the top end once you determine red clipping levels)

4) If green is 71% of the brightness of a display, and you set overall Brightness control to a proper level, what should be done once you bring blue/red back up and the brightness has changed, drop red/blue back down and lower green little by little until Brightness is proper with all cuts set appropriately?

5) How often during a calibration session should you "recalibrate" the sensor, assuming the use of an inexpensive colorimeter such as Eye-One Display2/LT?

I'm suprised nobody else has asked questions in this thread, hopefully for me that means I'll get all the attention.

Thank you to anyone with the knowledge to answer!
-Jason
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post #5 of 77 Old 01-19-08, 12:33 AM
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Re: Video Calibration Q&A

Short of spending 2 - 3K for ISF training what's a more modestly priced way to learn about the procedure and theory of calibration? I've read through the cal man online info a while back and it filled in some holes but I would really like to understand this stuff. I've had my TV calibrated so I won't be playing with mine in the near future but I would still like to learn.

Thanks much
-john

I'm checking out the links posted by Icaillo

Last edited by fibreKid; 01-19-08 at 12:46 AM.
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post #6 of 77 Old 01-19-08, 11:08 AM Thread Starter
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Re: Video Calibration Q&A

Quote:
Trekari wrote: View Post
I for one, greatly appreciate a general QA thread about calibration.

Over the past week, I borrowed a colorimeter from a local graphics shop and did a newbish effort at calibrating my display. I managed to get my grayscale rather accurate, but despite the picture looking much better than uncalibrated, there was a lot left to be desired.

So i'm going to do a factory reset and proceed with starting over.

Questions:

1) What is the first thing that should be adjusted. Contrast level to ~35fL for a plasma, then brightness?
Brightness first. It has a bigger affect on the top-end than a proper contrast control has on the low-end.

Quote:
2) Should ALL user controls be centered to 0 in order to set the above values in a service menu? (Contrast and Sub-Brightness)
There can be a significant interaction effect between SM controls and User Menu controls. Generally, try to stay out of the SM if at all possible. Once you are in, you are going to have to figure out the interaction.

Quote:
3) Is the "smart method" as I've heard it mentioned the best way to do brightness? i.e. Dropping red/blue bias/cut/offset/etc and only adjusting the green value, then bringing red/blue back up to proper levels? (similarly, using red gain as your 'max' level and adjusting green/blue on the top end once you determine red clipping levels)
I prefer to use the brightness control and a PLUGE pattern. I come back to check to make sure it hasn't been elevated or lowered too much after doing grayscale.

Quote:
4) If green is 71% of the brightness of a display, and you set overall Brightness control to a proper level, what should be done once you bring blue/red back up and the brightness has changed, drop red/blue back down and lower green little by little until Brightness is proper with all cuts set appropriately?
See my answer to #3, above.

Quote:
5) How often during a calibration session should you "recalibrate" the sensor, assuming the use of an inexpensive colorimeter such as Eye-One Display2/LT?
D2/LT? Once at the beginning.

Quote:
I'm suprised nobody else has asked questions in this thread, hopefully for me that means I'll get all the attention.

Thank you to anyone with the knowledge to answer!
-Jason
Looks like you got the ball rolling.

CalMAN -- Home Theater Calibration Software
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post #7 of 77 Old 01-19-08, 11:16 AM Thread Starter
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Re: Video Calibration Q&A

Quote:
fibreKid wrote: View Post
Short of spending 2 - 3K for ISF training what's a more modestly priced way to learn about the procedure and theory of calibration? I've read through the cal man online info a while back and it filled in some holes but I would really like to understand this stuff. I've had my TV calibrated so I won't be playing with mine in the near future but I would still like to learn.

Thanks much
-john

I'm checking out the links posted by Icaillo
We have now made CalMAN v3 downloadable by the general public, and not to be too biased, but the help system in it is probably the best resource for learning about calibration. We took the information in the original v1 document and added to it extensively.

You can download the application from here:
www.calman.tv/downloads/calmanv3_beta.msi

If this doesn't help, then the next step is either ISF or spending a few hundred on some video engineering texts and learning how to do it inductively.


Bill

CalMAN -- Home Theater Calibration Software
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post #8 of 77 Old 01-19-08, 05:28 PM
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Re: Video Calibration Q&A

Hi from my point of view when I first started calibrating it was the CalMAN V1 help which was for me the most informative and understandable infomation I found whilst trolling the web. I have found the V3(beta) information and help an excellent progressive step forward. I am not stating this because I use the software and get any reward from CalMAN. The rewards I get are from the excellent results I achieve from the software. I have to pay for it like everyone else( more $ actually as my NZ dollar sucks.)


ISF is more about buying into a support system of combined experience. You would only do this when or if you would be looking at being a calibrator of displays and wish to be more professional about your Image(In more ways than one). Many do the ISF seminar who are in the AV game and just what to understand more about what they do. It does cost though and it is up to the individual to weigh up or justify the outlay and return from the investment.

One never stops learning; painfully the more you know, the more you know you don't know.
On the other hand you don't need to learn electronics so you can calibrate display's. You in all reality just need a understanding of what is happening as a net result.

Order of calibration.
Just remember that all adjustments are interactive with the viewer, and it is this key element of total balance which possibly classes the calibrator in the professional sense.

I don't think there is any hard and fast rules on sequence, however brightness and contrast are the starting point for most if not all.
(again the CalMAN software helps you though this, other package struggle here, free or otherwise)
Personally I clump areas of the calibration process into groups. My reasoning for this is that looking at one point of view(one graph alone) gets you into trouble.

Calibration order is a lesser concern than the reference material you use and how accurate it can be processed. Your measurements are firstly only as accurate as your reference material, then add the error from your measurement device. This is why Video generators hold such high value as they are the most accurate reference for the calibrator. They also allow the calibrator to isolate the video chain which intern can solve problems or issues elsewhere.
Calibration DVDs are only as good as the device being used to play them. Electronics have a general tolerence of 10% in their common components, so the average output can vary. (my personal SD DVD player chopped off 10% of the lower end signal for example).
On the other hand some gear can be good too, but it can be an unknown quanity unless referenced to reference equipment.

This is how I rank the tools of the trade.

1. Reference material. Video Generator 1st, a Referenced PC output 2nd and thirdly a Calibration DVD material. I use a Video Generator and Calibration DVDs.

Reference material in general is ranked 1st,

2. Measurement probe. Many arguments about what is the best probe. Personally I have built a number of the HCFR probes, used a Spyder2 and use an xrite i1pro. I personally found the net results of my work better with the i1pro. It is currently the best all rounder. It is also the only (everyman)affordable NIST traceable referenced probe. If you are serious I recommend the i1pro, Calman(spectral cal) also rate the D2 probe very highly, I may get one of these some day as a secondary backup.

Measurement probe is ranked 2nd.

3. Software. Without the first 2 being accurate the software is rendered useless, that is why I place it third. I currently use the CalMAN V3 product and will be moving to the pro version when V3 moves from beta to general release.
Remember the software is really only a reporter of information, like any software we can have our favourites which is usually based on the product working how your head works. Some people call that intuitive. What ever the reason for me the software needs to be flexible and do the job, which is help you calibrate the display. Some products require alot of prior knowledge, some are flashy, one is currently free. I have used the free one with the DIY probes, Sencore software briefly, Datacolour software and CalMAN software, V2 (excel based) and V3beta. For me CalMAN is excellent hitpower for buck. The free software is excellent for learning though when one is in the early stages of the learning curve.

Software I rank third.

The forth element is the calibrator him or her self, here there is no rank per say, however one must have understanding of all of the above and what he or she is trying to achieve.

Regards

Light changes what it is doing depending if we are looking or not. Considering we only see this as a reflection of the past....what is it really doing now?
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post #9 of 77 Old 01-20-08, 12:25 AM
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Re: Video Calibration Q&A

Thank you Bear5K, I'll check it out.
-john
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post #10 of 77 Old 01-20-08, 09:54 PM
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Re: Video Calibration Q&A

Thank you very much for the replies! When my new meter arrives Wednesday I'll have to drag my PC into the living room and play for a few hours.

Hopefully the new meter arrives long before the new credit card bill.
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