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Ooops - D65 != D65 ???

Ooops - D65 != D65 ???

2007-06-18 by ulizappe

Hi everyone,

I originally posted the following in the ColorSync-Users list at apple.com, where I was told 
to post it here, too - so that's what I do :-)

Currently, I have several colorimeter/spectrophotometer packages at home for evaluation 
and comparison, the X-Rite/GM product range (Eye-One Display, Eye-One Pro, huey Pro) 
and the ColorVision Spyder2Pro.

Soon after starting to create test profiles, I realized that even if I set the 3 different X-Rite 
products all to exactly the same whitepoint/gamma settings, e.g. D65 G1.8, they 
produced profiles with *very* different whitepoints. Not surprisingly, the Spyder produced 
yet another different, forth whitepoint. (Measurement conditions were the same.)

Now, I'm aware that (speaking in terms of an xyY chromaticity chart) there's many different 
possible (x,y) combinations to produce a 6500 K whitepoint, but as far as I know a D65 
whitepoint is an unambiguous standard (x=0.3127, y=0.3290).

So I would think it should be reasonable to expect some kind of consistency (at least in the 
product range of *one single manufacturer* ...). What's the point of having a standardized 
D65 setting if it means something different to each measurement device? That doesn't 
exactly build confidence with regard to color management.

I'm very puzzled by this experience, and would appreciate comments from the experts in 
this forum. Do I expect something unreasonable? Do others experience consistent D65 
results and I'm doing something wrong (no idea what that could be, though)?

Thanks in advance for any insight

Bye

Uli

Re: [colorvision_group] Ooops - D65 != D65 ???

2007-06-19 by CDTobie@aol.com


In a message dated 6/18/07 9:03:33 PM, uli@... writes:


Now, I'm aware that (speaking in terms of an xyY chromaticity chart) there's many different
possible (x,y) combinations to produce a 6500 K whitepoint, but as far as I know a D65
whitepoint is an unambiguous standard (x=0.3127, y=0.3290).

Correct...

So I would think it should be reasonable to expect some kind of consistency (at least in the
product range of *one single manufacturer* ...). What's the point of having a standardized
D65 setting if it means something different to each measurement device? That doesn't
exactly build confidence with regard to color management.

D65 always means the same thing. 6500k can mean numerous things. ICC profiles always list (by definition) a D50 whitepoint. There is a document on the ColorVision website on proper transforms for monitor profiles not targetting D50, which has pretty much become the standard for the transforms used to adjust non D50 monitor whitepoints, so that they reconvert as expected. Using different transforms for this would explain differing results, as would minor differences in actual results when calibrating a monitor using different tools.

I'm very puzzled by this experience, and would appreciate comments from the experts in
this forum. Do I expect something unreasonable? Do others experience consistent D65
results and I'm doing something wrong (no idea what that could be, though)?

Don't expect identical results, even from the same tool used twice. Expect somwhat larger variations from differing software, and larger still from differing hardware and software, but all should be within reason. If they are way off, then thats an actual problem, rather than a statistical variation.

C. David Tobie
Product Technology Manager
ColorVision Business Division
DataColor Inc.
CDTobie@...
www.colorvision.com



**************************************
See what's free at http://www.aol.com.

Re: Ooops - D65 != D65 ???

2007-06-20 by ulizappe

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
> D65 always means the same thing. 6500k can mean numerous things. ICC profiles 
> always list (by definition) a D50 whitepoint. There is a document on the 
> ColorVision website on proper transforms for monitor profiles not targetting D50, 
> which has pretty much become the standard for the transforms used to adjust 
> non D50 monitor whitepoints, so that they reconvert as expected.

Do you have a link for that document? I had a look, but couldn't find it.

> Don't expect identical results, even from the same tool used twice. Expect 
> somwhat larger variations from differing software, and larger still from 
> differing hardware and software, but all should be within reason. If they are way 
> off, then thats an actual problem, rather than a statistical variation.

I posted my measurement results already in Apple's ColorSync-Users list, but they might 
be interesting for readers of this group, too, and I'd be interested in whether you would 
qualify these results as "being within reason", or rather as "an actual problem":

Target value: 6500 K

Eye-One Display:   0.315   0.341     6316 K
Eye-One Pro:       0.314   0.333     6407 K
huey:              0.307   0.328     6836 K
Spyder2Pro:        0.313   0.325     6510 K
                  (0.311   0.321     6657 K  with ICC v4; is the chromatic adaptation 
transformation lossy?)
(Kelvin calculated by entering the xy results into Spyder's "user-defined whitepoint" dialog 
panel)

Bye

Uli

Re: [colorvision_group] Re: Ooops - D65 != D65 ???

2007-06-20 by CDTobie@aol.com


In a message dated 6/20/07 12:44:30 AM, uli@... writes:


Do you have a link for that document? I had a look, but couldn't find it.

It does not appear to have made the leap to our new website But here is a description of the transform options, from other notes:

Chromatic Adaptation Mode
When recording colorimetric values in a profile, XYZ values need to be Chromatically Adapted from their measured color space to the D50 color space that is used by the ICC profile. There are different Adaptation Algorithms that can be used to perform this computation.

Bradford
The Bradford transformation is recommended by the ICC Specification and other sources as being the best adaptation method to be used. This is the default value in ColorVision software.

XYZ Scaling
Many other monitor profiling applications use the XYZ Scaling algorithm for Chromatic Adaptation when creating ICC profiles.

None
Prior to OptiCAL version 3.7.6, colorimetric values stored in ICC profiles created by this application did not undergo Chromatic Adaptation. This option no longer offered in recent ColorVision software.


> Don't expect identical results, even from the same tool used twice. Expect
> somwhat larger variations from differing software, and larger still from
> differing hardware and software, but all should be within reason. If they are way
> off, then thats an actual problem, rather than a statistical variation.

I posted my measurement results already in Apple's ColorSync-Users list, but they might
be interesting for readers of this group, too, and I'd be interested in whether you would
qualify these results as "being within reason", or rather as "an actual problem":

Target value: 6500 K

Which can be met by an infinite number of xy pairs... as was explained much earlier in your thread.

Eye-One Display: 0.315 0.341 6316 K
Eye-One Pro: 0.314 0.333 6407 K
huey: 0.307 0.328 6836 K
Spyder2Pro: 0.313 0.325 6510 K
(0.311 0.321 6657 K with ICC v4; is the chromatic adaptation
transformation lossy?)
(Kelvin calculated by entering the xy results into Spyder's "user-defined whitepoint" dialog
panel)

All of these values are probably within the published accuracy specs of the devices involved. You seem to be looking for absolute numbers from end user devices. Even laboratory Minolta meters costing nearly as much as my car have an accuracy spec that would allow for about this much variation. You need to have some perspective on this issue: spend tens of thousands of dollars on two Minolta lab meters, measure the same screen with both of them, get results which vary by, say, 200 or 300 K... thats just the tolerances one gets in this field. Coverted from little x, little y values with variations in the hundredths, to K values that are hundreds different; it sounds big, but thats the math fooling you.

C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com



**************************************
See what's free at http://www.aol.com.

Spyder not being recognised again

2007-08-30 by John Malcolm

Had to do reinstall of the graphics drivers on my machine and now 
Spyder2Pro is not being recognised again. When this last happened I had 
to download the Spyder2Pro drivers from the Datacolour FTP site.  
(ftp://212.243.137.190) FTP address is not working now. Can someone 
give me a current FTP address, login and password please? Or, would 
someone kindly post me the AMD64/XP64 drivers for Spyder2Pro.

Many thanks

Re: Spyder not being recognised again

2007-08-30 by marko.mili

--- In colorvision_group@yahoogroups.com, "John Malcolm" <johnmalcolm@...> wrote:
>
> Had to do reinstall of the graphics drivers on my machine and now 
> Spyder2Pro is not being recognised again. When this last happened I had 
> to download the Spyder2Pro drivers from the Datacolour FTP site.  
> (ftp://212.243.137.190) FTP address is not working now. Can someone 
> give me a current FTP address, login and password please? Or, would 
> someone kindly post me the AMD64/XP64 drivers for Spyder2Pro.
> 
> Many thanks
>

You can download Spyder2Pro software from www.colorvision.com in the support section. 
Just use your own serial to register it, when program starts for the first time.

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