Mark Hunter from Milori Colorfacts 14-18 Januari.

Started by J.A.F._Doorhof, January 3, 2003, 21:28:04

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FrankL

Rob, Frank,

What is gain?
Do you mean the RGB settings in the system menu 'custom color temperature', the ones I adjust during greyscale calibration?

And Rob, what do you mean with 'check individual colors on the avia pattern'? What avia pattern?

Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

J.A.F._Doorhof

Gain, Drive, Contrast.
Indeed the R,G,B values you change in the grayscale calibration for the top of the scale.

Greetings,
Frank
www.hometheater.nl   /   ISF & HAA certified
Custom installer

Volledige ISF calibraties inclusief HDR en 4K.

"Omdat je je iets niet kan voorstellen betekent dat niet dat het niet kan gebeuren"

FrankL

OK, thanks, I'll try that.

Mark,

Yesterday I tried out my FL-D (daylight) filter.
This is the RGB result of my calibration without the filter:



I added the FL-D filter to my Piano, did the Device Primaries reading and recalibrated. This was the result:



As you can see, it is a similar graph, but the scale of the Y('%')-axis seems to be completely different.
Do you have an explanation for this?

Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

Mark Hunter

Wow!  You guys get active on the week-ends!  ;D

FrankL - As Frank D. noted, the "gain" I mentioned goes by different names sometimes.  It could be called SubContrast, Drive or Gain.  I say SUBContrast, as we were really hoping for the settings for the individual Red, Green and Blue values.  The overall Contrast setting moves all three together, and won't help much here.

I hope that your display has individual high level controls and low level controls...it looks like we're going to need them...

No matter if you have the filter in place or not, it looks like you need more Red on the top end, and less Red on the bottom end.  The only way to do this will be with individual color controls.  If there is a SubContrast, Drive or Gain control, you will want to increase that setting to add some Red to the high end.

Unfortunately, since you already have too much Red on the low end (esp. after the filter addition!), you will need to also decrease the Red settings on the lower end (often called SubBrightness, Bias, Offsets or Cuts).

Just off-hand, I'd say that the filter didn't help the picture a whole lot yet  ;D

FrankL

Unfortunately, I do not have those settings.
There is a custom gamma setting for RGB individually, but I'm not sure what that does. Here you can set an index, and Red/Green/Blue. The manual (as usual for manuals) is very cryptic: "The adjustment permits the creation of a desired gamma curve".
Decreasing red on the lower end, end raising it on the higher end, sounds a bit like gamma adjustment  ???
Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

J.A.F._Doorhof

Frank,

How do you normally calibrate the grayscale ?

Normally we adjust R,G,B on the top and bottom.
It has been a while that I did a Piano, but is there only one setting for R,G,B in color temperature ?

Greetings,
Frank
www.hometheater.nl   /   ISF & HAA certified
Custom installer

Volledige ISF calibraties inclusief HDR en 4K.

"Omdat je je iets niet kan voorstellen betekent dat niet dat het niet kan gebeuren"

Mark Hunter

Frank L,

Gamma may be the ticket!  That's the "look-up table" that converts incoming voltage to output luminance.  If you can adjust the R/G/B separately using the "gamma" feature, you likely have all that you need to calibrate it!

Are the R/G/B separately adjustable, on the high and low end (closer to white and closer to black) in the "gamma" setting?

Mark

FrankL

FrankD, there is only one setting for RGB in color temp, no separate setting for low end / high end.  :(

Mark, there are separate adjustments in custom gamma for R,G,B, but no separate settings for low / high.
I'll look into it, if I can finetune the greyscale using the custom gamma.

But for tonight, it's movietime  :)

Mark, what did you think about the way I adjusted the contrast? (See previous post).
Thanks again for your input!
Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

FrankL

#33
Quote from: Rob_Dingen on January 18, 2003, 09:51:13
I think you maybe can get some more lightoutput
What are your gain settings from red RGB and what are the maximum
As a quick test crank up the rgb gain settings and adjust contrast and see if the bars dissapear with the avia pattern you mentioned before
You also can check invidual colors on the avia pattern and see when they dissapear
Hi Rob,

Interesting!!
The default setting for RGB in the custom color menu is 0. If I crank all 3 up to 20, I can get both white bars to dissappear (the settings go to 127 max setting).  :)

So this raises another 2 questions  ;D :
- will this (i.e. increasing the RGB settings to a level where I can set contrast correctly) increase the contrast ratio of my projector?
- how do I find the balance between overall RGB level and contrast setting, since both raise the contrast!

BTW, Rob, I'm still wondering what you mean by 'You also can check invidual colors on the avia pattern and see when they dissapear'.

Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

Rob_Dingen

Hello FrankL

I mean the avia white bars
Crank up red and see when they dissapeer lower green and bleu
Do that with all 3 and adjust the color with the weakest output to max and adjust the other colors for 6500k

Rob

FrankL

Thanks Rob.
So you're saying: when doing the greyscale calibration, lock the 'weakest color'. No problem, as you can read here, I can lock the weakest color in Colorfacts, so that the other colors in the RGB graph are relative to the locked color. (I'm mentioning that to be at least a little bit 'on topic'  ;) )

However, IMO there is a relation to the overal contrast setting. How do I find the balance between the level of the weakest color in the RGB temperature, and the overall contrast setting  ???
Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

J.A.F._Doorhof

Hi,

A bit difficult if you have only ONE point for your grayscale calibration.

What you could do:
Set brightness and contrast with AVIA, so the blackbars are seen on the black bars screen, and the white bars are seen on the pluge screen.

Now calibrate your grayscale to D6500K.
Now take the pluge screen and set your analyzer in the white field. Make sure that you still read the same temp as with the 100IRE field, if not take the new temp as your reference.
Now raise R, G, B 1-2 points a time untill you see the white bars dissapear. And than back it of 1-2 points again.
Keep monitoring the temperature, it SHOULD not change, however because you are using a one point calibration it COULD.

After you did this, check the whole grayscale again, ideally this should have not affected the grayscale, but it probarbly will.

If the picture has alot more punch but you have to suffer linearity judge for yourself if it's worth it, aiming for +/- 250 degrees for better contrast ratio is good, more than 500 degrees offset between 30-80 IRE is not advisable.

Greetings,
Frank
www.hometheater.nl   /   ISF & HAA certified
Custom installer

Volledige ISF calibraties inclusief HDR en 4K.

"Omdat je je iets niet kan voorstellen betekent dat niet dat het niet kan gebeuren"

FrankL

Hi FrankD,

Thanks, this sounds like a good way to do it.
However, there is still the small 'problem'  that with the standard RGB settings (of 0), I see the white bars with every contrast setting. So there is no way to decide with which contrast setting to start. Maybe it is irrelevant. Maybe there is no difference between ending up with let's say a contrast of 50 and a RGB average of 30, or a contrast of 20 and a RGB average of 60. But maybe it does make a difference  ???
Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

J.A.F._Doorhof

It all depends a bit of what contrast does on your setup.
That's what we (as calibrators) have to find out every calibration of a new chasis. ;D

I would start with a contrast setting of 95% and work from there.
Why not 100% ?
I found out that on SOME digital projectors the 100% setting crushes the white level and affects the behaviour of the gamma (although that should not happen).

Look closely at your readings and interprent them the correct way and you should see the puzzle solve itself fairly quick.

Greetings,
Frank
www.hometheater.nl   /   ISF & HAA certified
Custom installer

Volledige ISF calibraties inclusief HDR en 4K.

"Omdat je je iets niet kan voorstellen betekent dat niet dat het niet kan gebeuren"

Mark Hunter

Hello, Gentleman!

I just wanted to thank you for having me as a special guest on your forum!  It was my pleasure being here and discussing calibration techniques with you.

Thank you very much for the invitation!

Sincerely,

Mark Hunter
ColorFacts Team

FrankL

Hi Mark,

Thanks for being here! Your input was highly appreciated.

Frank
Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95

MrPink

Hi Mark,

Even though I couldn't follow most of what was said, I do appreciate you answering all the questions! :)

Ciao,
Oscar

J.A.F._Doorhof

Hi,

Thanks, and I hope you will drop by sometimes.

Greetings,
Frank
www.hometheater.nl   /   ISF & HAA certified
Custom installer

Volledige ISF calibraties inclusief HDR en 4K.

"Omdat je je iets niet kan voorstellen betekent dat niet dat het niet kan gebeuren"

FrankL

Quote from: Mark Hunter on January 15, 2003, 17:36:45
The new ColorFacts CF-6000 spectroradiometer that we introduced at CES is an extremely accurate device. In fact, the CF-6000 won the accuracy shoot-out against the new Sencore and Progressive Labs offerings.

The Sencore CP-288 is a device with silicon photodetectors under colored gel filters. The colors of the gel filters are specifically matched to SMPTE-C, and will work great with devices that conform to that specification (read: CRT monitors).

However, fixed panel display devices do not match this spec (see SGHT or WideScreen Review magazines to see how far off they measure). For these devices, the CP-288 will produce "unknown" results.

For this reason, Sencore introduced the CP-5000, which they say is the "All Display Calibrator" and will work with any display device (not just CRT monitors). They brought this device to the accuracy shoot-out. Their new product is very expensive for what it is ($5000 USD), and our CF-6000 was shown to be more accurate (see here: http://www.colorfacts.com/colorfacts/news/20030114.asp), and less expensive ($1995 USD).

Well, it's a bit of an overkill for the Piano, but Sum1 and I decided to use the upgrade offer. In a few weeks, we will have the CF-6000. We will be able to calibrate directly off the screen. 8) 8) 8)
I will do some new measurements, like measuring contrast in different area's of the screen, to see what the reflection of the white ceiling does to the contrast ratio.

This is becoming an expensive hobby ;)
Marantz VP-15S1
Denon AVC-A1SR-A
Oppo 95