Video Calibration Q&A

[Bear5K]

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

[Sonnie]

Thanks Bill... we appreciate your knowledge.

[lcaillo]

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.

[Trekari]

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

[fibreKid]

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

[Bear5K]

Trekari wrote:

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.

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.

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.

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.

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.

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.

[Bear5K]

fibreKid wrote:

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

[<^..^>Smokey Joe]

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

[fibreKid]

Thank you Bear5K, I'll check it out.
-john

[Trekari]

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.

[Zee]

OK, so, I run a business installing home theaters. Been doing it for a long time, but I want to take the next step.

I've looked into the ISF course, and was wondering if the CalMAN pro software with Eye one pro will:
Be fine for LCD, Plasma AND projection (I can never seem to get a straight answer when I search probes).

And, secondly, is it to "ISF standards"? I'm sure the Colorfacts pro software is wonderful, but geez.. it's pricey.

And finally, how does a Spider 3 compare to the eye one Pro?

Thanks for the help...

Z...

[Bear5K]

Zee wrote:

OK, so, I run a business installing home theaters. Been doing it for a long time, but I want to take the next step.

I've looked into the ISF course, and was wondering if the CalMAN pro software with Eye one pro will:
Be fine for LCD, Plasma AND projection (I can never seem to get a straight answer when I search probes).

Yes, but with a caveat. If you have to use only one meter as a Pro due to budget constraints, then the i1 Pro is it. After it, you start to get into meters costing several thousand dollars (US Pesos, really; the last time I was in Australia, the Aussie dollar was at US$0.67). The caveat is that this leaves you with a single point of failure for your business (they ought to be recalibrated every year, and they do break occasionally). Many of our professionals like to use a meter like a Chroma 5 or DisplayLT as a lower cost "back-up", that also helps with setting the grayscale controls on the new, higher-contrast direct-view displays (e.g., Pioneer Kuro). We sell kits at a lower cost for either of these options (i1 Pro + Pro software; i1 Pro + Chroma 5 + Software) on our website.

And, secondly, is it to "ISF standards"? I'm sure the Colorfacts pro software is wonderful, but geez.. it's pricey.

This is essentially why we got into business. With all due respect to Joel Silver, the ISF does not actually set the standards. The standards are set by organizations like the Society for Motion Picture and Television Engineers (SMPTE; I'm a member), the International Telecommunications Union (ITU) and the European Broadcasting Union. In fact, any time you see "Rec. 709" (aka HD), this is really shorthand for ITU-R Recommendation BT.709-XX (with XX being the current revision number).

We are trying to get onto the ISF "approved" list, but they had a six month backlog of paid evaluation work they were trying to complete. Expect to see this happen eventually.

And finally, how does a Spider 3 compare to the eye one Pro?

It's a decent option for LCDs or DLPs, but we can't recommend it for CRT and plasma use yet. I also would not use it with any type of "spiky" light source (e.g., LED-based light engines). We also tend to steer professionals away from meters that are available at the local computer shop. There's a bit of a branding issue here (fee justification).

HTH!

Bill

[Zee]

Excellent - that pretty much covers all I need to know.
Also, thanks for enlightening me on the ISF/SMPTE and standards issue.

I did notice the package price for the pro software and i1pro was particularly good. Local Aussie pricing is insane, in particular considering how well placed our currency is right now.

I expect to be placing an order soon. thanks for your help.
Cheers,

Z...

[Bear5K]

Download the evaluation software, as well. The documentation should give you a jumpstart on all of this.

[Zee]

Good idea - thanks for the suggestion.

Cheers

Z...

[Rambo4]

I am unsure if my question here is out of place as I have no real knowledge of a lot of what has been said above.

I do know that I have a display issue in my projector, that I am unsure if it is something mechanical or just my setup. I have an IN76 projector viewed on a 92" screen, distance to screen is approx. 12 feet. Everything looks as it should doing video calibration tests, but I have this slight dip in the lower right hand corner of the image. As far as I can tell there is no adjustment in the menu for fixing one corner of the image. I do see it there when I run test images. The screen is flat and bordered (Screen Innovations) so that shouldn't be culprit. It's not really noticeable when watching a movie. As I said it is slight and gets worse toward the corner.

Should I get out my level? Or should I call the tech guys at Infocus for their opinion on a repair?

[lcaillo]

Please start a new thread for your problem.

I'd start by checking centering and level. Look very carefully at the other side. You will likely see a similar problem.