Basic Guide to Color Calibration using a CMS (updated and enhanced) - Page 8 - AVS Forum
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post #211 of 1936 Old 09-04-2007, 09:43 AM
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Hi all,

Is there any preference as to whether one should select a device to output HDMI RGB as opposed to component HDMI YCbCr (providing the device supports both - see PS3, oppo 970hd etc), when calibrating a system?

If so what is the compromise (if any) with some source devices which only output HDMI YCbCr (ie a Sat Reciever, tosh HDDVD hd-e1 (or ax1 in US I think) etc)

My thinking is since most of the digital displays will output anything (over HDMI) as HDMI RGB, it is better to have the source outputting HDMI RGB too (?) avoiding any color space issues that come from sources mis-matching SD ITU 601 to HD ITU 701 when using HDMI component (thinking of upscaling/upconverting players here). But is it the case?

Many thanks,

Kostas
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post #212 of 1936 Old 09-08-2007, 01:56 PM
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Quote:
Originally Posted by TomHuffman View Post

This is not what we mean by a Color Management System. The NTSC specification requires ALL displays to have adjustments for Color, Tint, Sharpness, Brightness, and Contrast. A CMS goes significantly beyond this.

I really liked your instructions, they arevery clear, I only have some terminology problems. I own a Sony HS60 and it has Color, Hue, Brightness, Contrast and Sharpness, also individual RGB Gain/Bias.

There is no tint? How does this effect your instructions?
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post #213 of 1936 Old 09-08-2007, 02:50 PM
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Quote:


There is no tint? How does this effect your instructions?

hue = tint

-Greg
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post #214 of 1936 Old 09-09-2007, 12:09 AM
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Quote:
Originally Posted by angryht View Post

hue = tint

Thank you. I got confused because in the first post both terms are used, why?

Steps from the first post:
Setting Color/Tint
Adjust the gray scale
Adjusting the Color Decoder
Adjusting Hue and Saturation

Saturation = color or is it?
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post #215 of 1936 Old 09-09-2007, 09:16 AM
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Tom,

Is it possible to answer my question in post 213? It'd really help clarifying things (at least for me but I am sure for others as well).

Many thanks,

Kostas
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post #216 of 1936 Old 09-09-2007, 09:56 AM - Thread Starter
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If your signal path uses a digital RGB signal you should avoid any color decoding problems. Otherwise, so long as both source and display are properly configuried and working correctly I don't see that it would make any difference.

Quote:
Originally Posted by kopa13 View Post

Hi all,

Is there any preference as to whether one should select a device to output HDMI RGB as opposed to component HDMI YCbCr (providing the device supports both - see PS3, oppo 970hd etc), when calibrating a system?

If so what is the compromise (if any) with some source devices which only output HDMI YCbCr (ie a Sat Reciever, tosh HDDVD hd-e1 (or ax1 in US I think) etc)

My thinking is since most of the digital displays will output anything (over HDMI) as HDMI RGB, it is better to have the source outputting HDMI RGB too (?) avoiding any color space issues that come from sources mis-matching SD ITU 601 to HD ITU 701 when using HDMI component (thinking of upscaling/upconverting players here). But is it the case?

Many thanks,

Kostas


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post #217 of 1936 Old 09-12-2007, 11:56 PM
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Quote:
Originally Posted by TomHuffman View Post

If your signal path uses a digital RGB signal you should avoid any color decoding problems. Otherwsie, so long as both source and display are properly configuried and working correctly I don't see that it would make any difference.

Hi Tom,

Is there something that could be used to verify that source and display are working correctly? How could this be seen?

Another question about this step in your instructions:
Color
" 1. Point the colorimeter or light meter towards the screen and display a 75% white window. It is important that you use a window, not a full screen.
2. Measure the Y value of white (this is essentially the brightness or intensity of the white window).
3. Display a 75% Red window, and measure the Y value here as well.
You will notice that as you move the Color control up and down, the Y value of Red increases and decreases, but white stays the same.
4. Set the color control at the point where Red measures closest to 21% of the white reading."

I'm using Spyder2, HCFR and GetGray. Sensor points to screen, maybe 20cm distance. I have configured HCFR: Sensor->Calibration->"IRE level images to 75", is this ok or does it matter at all when measuring the above step?

I followed your instructions and used continuous mode in HCRF to measure xyY (looking at values in Measures window) for the 75% white window (Y value was ~5.3) then switched to 75% red window (Y value was ~0.5), but no matter how I moved the Color setting in my HS60 projector it did not seem to make much difference. Maybe moved from 0.4-0.6. Whats wrong here?
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post #218 of 1936 Old 09-13-2007, 07:10 AM - Thread Starter
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Quote:
Originally Posted by JoeFinn View Post

I'm using Spyder2, HCFR and GetGray. Sensor points to screen, maybe 20cm distance. I have configured HCFR: Sensor->Calibration->"IRE level images to 75", is this ok or does it matter at all when measuring the above step?

I followed your instructions and used continuous mode in HCRF to measure xyY (looking at values in Measures window) for the 75% white window (Y value was ~5.3) then switched to 75% red window (Y value was ~0.5), but no matter how I moved the Color setting in my HS60 projector it did not seem to make much difference. Maybe moved from 0.4-0.6. Whats wrong here?

Do not change that setting to 75. Leave it at its default of 100.

You may be below the threshold at which the sensor can get reliable readings. Try using 100% white and red windows, and position the sensor no more than 18" from the screen.

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post #219 of 1936 Old 09-13-2007, 07:53 AM
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Quote:
Originally Posted by TomHuffman View Post

Although there are no hard and fast rules about this, I would make color adjustments in the following order:

- Color/Tint
- Gray scale
- Color decoding
- Color gamut

Tom if you have a CMS which has RGBCMY controls do you just skip the Color/Tint stage and leave them at unity?? I'm guessing you set brightness and contrast first.
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post #220 of 1936 Old 09-13-2007, 09:43 AM - Thread Starter
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Quote:
Originally Posted by hosko View Post

Tom if you have a CMS which has RGBCMY controls do you just skip the Color/Tint stage and leave them at unity?? I'm guessing you set brightness and contrast first.

Yes, if the CMS includes a full compliment of controls over saturation, hue, and brightness. For example the Epson 1080p has saturation and hue controls, but no adjustment for color brightness. Thus, you must consider the user Color control.

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post #221 of 1936 Old 09-13-2007, 11:20 AM - Thread Starter
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I deleted the post containing a database of displays with a CMS and added it to the end of the initial article. I also clarified some information about the use of 75% windows for color adjustments.

Tom Huffman
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post #222 of 1936 Old 09-13-2007, 11:29 PM
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Quote:
Originally Posted by TomHuffman View Post

Do not change that setting to 75. Leave it at its default of 100.

You may be below the threshold at which the sensor can get reliable readings. Try using 100% white and red windows, and position the sensor no more than 18" from the screen.

I bought Eye-One LT because people here seem to think it is much better than Spyder2. Hopefully I did not waste my money, plus I hope it is alot faster than Spydey
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post #223 of 1936 Old 09-14-2007, 12:49 AM
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Does anybody know if the Sony XBR4/5 has a full CMS?? I don't get my 52" till the start of October when Sony Australia receives their stock
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post #224 of 1936 Old 09-14-2007, 06:12 AM
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Hi Tom, thanks for this great threat and your tips! I am awaiting Spyder2 and downloaded HCFR software and dvd with test images and want to calibrate my Epson TW1000. It will be my first serious calibration attempt. I remember you calibrated him once, have you some specific tips for this projector, or should i simly try follow the instruction on the first site of this threat?
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post #225 of 1936 Old 09-14-2007, 08:08 AM - Thread Starter
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Quote:
Originally Posted by talkron View Post

Hi Tom, thanks for this great threat and your tips! I am awaiting Spyder2 and downloaded HCFR software and dvd with test images and want to calibrate my Epson TW1000. It will be my first serious calibration attempt. I remember you calibrated him once, have you some specific tips for this projector, or should i simly try follow the instruction on the first site of this threat?

Nothing special. Calibration with its CMS and gray scale controls is straightforward. It has no controls for the color decoder. The upcoming Epson TW2000 UB will have.

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post #226 of 1936 Old 09-14-2007, 08:11 AM - Thread Starter
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Quote:
Originally Posted by hosko View Post

Does anybody know if the Sony XBR4/5 has a full CMS?? I don't get my 52" till the start of October when Sony Australia receives their stock

It does not.

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post #227 of 1936 Old 09-14-2007, 02:17 PM
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Quote:
Originally Posted by robbyc30 View Post

On another subject, I beleive it was Tom that mentioned that my RGB levels (especially Green) were lower than should be necessary for a proper calibration on this unit. The reason they were so low was my method, posted on the forum quite awhile back, by Guy Quo. His method was basically, center Brightness/Contrast, set Red and Blue Offset too low and use Green Offset to set Brightness (make BTB match backround). Return Red and Blue Offsets to default. Then, set Red Gain to highest that doesn't cause clipping. Then use only the Green and Blue Gains, and the Red and Blue Offsets to calibrate. I've always assumed this was correct. I mean Guys knows what he's talking about...right?

Rob

robbyc30,

I was rereading this thread (again) and I came across the quote above. I was wondering if you or anyone else had a link to this method or if you could answer a few questions about it.



1. How do you:
Quote:


use Green Offset to set Brightness (make BTB match backround)

. Do you put up the pluge pattern (or other - i.e. getgray) and just use the green offset to adjust the brightness of the black?

2. How do you:
Quote:


set Red Gain to highest that doesn't cause clipping

. Would you put up 100% stimulus and increase red gain until it starts to drop off in the continuous measures?

3. Is the purpose of this method to get the best range without having the gains and offsets clip? I thought I saw something similar in the Smart III documentation from years ago.

Anyway, sorry if this isn't the right place for this question but I would appreciate any direction.

-Greg
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post #228 of 1936 Old 09-15-2007, 09:34 PM
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Quote:
Originally Posted by TomHuffman View Post

It does not.

Is it missing CMY controls?
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post #229 of 1936 Old 09-15-2007, 09:48 PM - Thread Starter
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It has no CMS at all so far as I can tell. Just color temp adjustments.

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post #230 of 1936 Old 09-15-2007, 11:15 PM
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Quote:
Originally Posted by TomHuffman View Post

It has no CMS at all so far as I can tell. Just color temp adjustments.

It has RGB gain and bias in the user menu
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post #231 of 1936 Old 09-16-2007, 05:52 PM
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I don't have a link, but I found a prinout that I will re-type for you. As far as the questions:
1) Yes.
2) I think the way I did it, which I believe is an acceptable method, was to put up a 100IRE screen and adjust the Red Gain until the Red value stops increasing. I actually ended up having to lower mine to -6 I believe.
3) I'm not sure of the benefits of using this method. I've wondered if the end results would be significantly different than just using the Brightness and Contrast settings. I just passed 100 hrs, so at some point I need to do a touch-up, and plan on checking this.

Here's the post from Guy Kuo:

"For most digital projectors which are red limited output, I'd do the following to get contrast and brightness, gains and biases set.

As a preliminary, set contrast and brightness to middle settings. Then go into the grayscale adjustments and use them to get grayscale, white and black correct.

1. Turn red and blue bias a good ways down to intentionally set them too low
2. Set green bias to make the blacker than black stripe match black (digital 16) backround.
3. Return red and blue bias to previous settings and from here on leave the green bias alone!
4. Set red gain to the highest that doesn't cause the top end output to be red deficient. That means the highest setting of red gain that doesn't cause red to clip. You can pretty easily see this by looking for a color shift of the 90, 100, and above white stripes in Avia Pro. Once this is done leave red gain alone.
5. Adjust gray scale using only the green and blue gains for the top end. Use only the red and blue bias controls for adjusting the bottom end of the grayscale. Leave the red gain and the green bias alone while adjusting the grayscale."

Rob



Quote:
Originally Posted by angryht View Post

robbyc30,

I was rereading this thread (again) and I came across the quote above. I was wondering if you or anyone else had a link to this method or if you could answer a few questions about it.



1. How do you: . Do you put up the pluge pattern (or other - i.e. getgray) and just use the green offset to adjust the brightness of the black?

2. How do you: . Would you put up 100% stimulus and increase red gain until it starts to drop off in the continuous measures?

3. Is the purpose of this method to get the best range without having the gains and offsets clip? I thought I saw something similar in the Smart III documentation from years ago.

Anyway, sorry if this isn't the right place for this question but I would appreciate any direction.

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post #232 of 1936 Old 09-16-2007, 09:11 PM - Thread Starter
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Quote:
Originally Posted by hosko View Post

It has RGB gain and bias in the user menu

Yes, that's the color temp adjustments.

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post #233 of 1936 Old 09-16-2007, 10:40 PM
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Quote:
Originally Posted by TomHuffman View Post

Yes, that's the color temp adjustments.

Which means I can adjust Grey Scale but that's about it?
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post #234 of 1936 Old 09-17-2007, 06:58 AM - Thread Starter
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Quote:
Originally Posted by hosko View Post

Which means I can adjust Grey Scale but that's about it?

Yep.

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post #235 of 1936 Old 09-17-2007, 07:51 AM
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Quote:
Originally Posted by robbyc30 View Post

I don't have a link, but I found a prinout that I will re-type for you. As far as the questions:
1) Yes.
2) I think the way I did it, which I believe is an acceptable method, was to put up a 100IRE screen and adjust the Red Gain until the Red value stops increasing. I actually ended up having to lower mine to -6 I believe.
3) I'm not sure of the benefits of using this method. I've wondered if the end results would be significantly different than just using the Brightness and Contrast settings. I just passed 100 hrs, so at some point I need to do a touch-up, and plan on checking this.

Here's the post from Guy Kuo:

"For most digital projectors which are red limited output, I'd do the following to get contrast and brightness, gains and biases set.

As a preliminary, set contrast and brightness to middle settings. Then go into the grayscale adjustments and use them to get grayscale, white and black correct.

1. Turn red and blue bias a good ways down to intentionally set them too low
2. Set green bias to make the blacker than black stripe match black (digital 16) backround.
3. Return red and blue bias to previous settings and from here on leave the green bias alone!
4. Set red gain to the highest that doesn't cause the top end output to be red deficient. That means the highest setting of red gain that doesn't cause red to clip. You can pretty easily see this by looking for a color shift of the 90, 100, and above white stripes in Avia Pro. Once this is done leave red gain alone.
5. Adjust gray scale using only the green and blue gains for the top end. Use only the red and blue bias controls for adjusting the bottom end of the grayscale. Leave the red gain and the green bias alone while adjusting the grayscale."

Rob

Thanks, robby, that is exactly what I was looking for. I appreciate the retyping efforts.

I am still a little confused, though. This seems to be a method to maximize the offsets and gains so there is not clipping of green (on the low end) and red (on the high end). This is similar to the SMART system by Steve Smallcombe that I have read about but never tried. It just seems that only using the green bias to adjust the black level, then bring up the red and blue bias and get to color temp of 6500K. Is there more context? Do you set overall black and white levels again after the color temp is set? I need a little more enlightenment.

On a side note, if these posts seem to be inapproprate for this thread, I would ask that the moderator move them to this thread: http://www.avsforum.com/avs-vb/showt...1#post11631891

Thanks.

-Greg
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post #236 of 1936 Old 09-17-2007, 08:05 AM
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thanks ! I have only two more little questions: how to set right the skin tone correction(i belive it regulates the amouth of green in the picture) and(little off topic) is there a simple rule how to set contrast(i use for this usualy the THX optimizer pattern, but with TW1000 there is huge up and down room in which the pattern still loks right)
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post #237 of 1936 Old 09-17-2007, 08:38 AM - Thread Starter
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Quote:
Originally Posted by talkron View Post

thanks ! I have only two more little questions: how to set right the skin tone correction(i belive it regulates the amouth of green in the picture) and(little off topic) is there a simple rule how to set contrast(i use for this usually the THX optimizer pattern, but with TW1000 there is huge up and down room in which the pattern still looks right)

This is getting a little far afield from color calibration and moving towards general questions about a specific device. In any case, yes, the skin tone correction just affects the amount of green in the gray scale. If I recall 3 was the most neutral setting.

You look for several things in setting contrast.
  • Does the set clip whites on the high end? If so, you need to reduce contrast.
  • Do you see any color shifting at peak output? If so reduce contrast.
  • Does ordinary viewing cause fatigue or eye strain? If so, reduce contrast.
So, the general rule of thumb is to set contrast at the highest level that none of these occur. 35 fL is a good target for CRTs, flat panels, and rear projection. 15 fL is a good target for front projection.

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post #238 of 1936 Old 09-17-2007, 09:02 AM
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Quote:
Originally Posted by TomHuffman View Post

This is getting a little far afield from color calibration and moving towards general questions about a specific device. In any case, yes, the skin tone correction just affects the amount of green in the gray scale. If I recall 3 was the most neutral setting.

You look for several things in setting contrast.
  • Does the set clip whites on the high end? If so, you need to reduce contrast.
  • Do you see any color shifting at peak output? If so reduce contrast.
  • Does ordinary viewing cause fatigue or eye strain? If so, reduce contrast.
So, the general rule of thumb is to set contrast at the highest level that none of these occur. 35 fL is a good target for CRTs, flat panels, and rear projection. 15 fL is a good target for front projection.

Can HCFR be used to measure fL values (foot Lambert) or do I need a seperate meter?

I have very big problem with my contrast and I don't know what to blame. I have a bat cave, Stewart Grayhawk RS, Sony HS60 (contr = 57, zoom is at the smallest picture setting), VP30(contr=-15) and even now the picture seems to bright?? This does not seem normal to me, but maybe the HS60 is simply a light cannon?
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post #239 of 1936 Old 09-17-2007, 10:58 AM - Thread Starter
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Quote:
Originally Posted by JoeFinn View Post

Can HCFR be used to measure fL values (foot Lambert) or do I need a seperate meter?

I have very big problem with my contrast and I don't know what to blame. I have a bat cave, Stewart Grayhawk RS, Sony HS60 (contr = 57, zoom is at the smallest picture setting), VP30(contr=-15) and even now the picture seems to bright?? This does not seem normal to me, but maybe the HS60 is simply a light cannon?

The HS60 is NOT a light canon. It uses a 135W bulb if I recall. For a front projector I don't think you can use HCFR to measure foot lamberts. If someone knows how, then speak up.

If I were you I would purchase an AEMC CA813 light meter, which you can get online for about $150. Then:
  1. Use a test DVD to play a full white window (100 IRE).
  2. Place the meter at the screen facing the projector.
  3. Set the meter to read in Lux.
  4. Use the following formula to determine fL.
(Lux/10.76)*screen gain=fL

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post #240 of 1936 Old 09-17-2007, 11:25 AM
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I am pretty sure that HCFR measures Y candela per square meter (Y=cd/m^2). Doesn't 1 candela / (meter^2) = 1 lux?

-Greg
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