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3 questions concerning calibration procedures with spyder express/ 2suite/ pro

3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-22 by esimanor

1.Do you know if one could possibly update software at later stage from 
Spyder Express to say Syder 2 Suite or even Spyder pro since it seems 
as if all use the same spyder device?

2.Can one select "Native" gamma and white point temperature using 
Spyder 2 Suite or spyder Pro software/

3.can one manually select his own white and black point luminance 
settings in the calibartion process using Spyder express? what about 
spyder Pro?

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-22 by John Vitollo

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> wrote:

> 2.Can one select "Native" gamma and white point temperature using 
> Spyder 2 Suite or spyder Pro software/

I'm using Spyder2PRO...only "Native" white point temp can be selected. No settings for native 
gamma. This is with a Dell 1905FP LCD.

> 3.can one manually select his own white and black point luminance 
> settings in the calibartion process using Spyder express? what about 
> spyder Pro?

With the Spyder2PRO manually inputing White Luminance values works fine...but the Black 
Luminance seems to be anchored at 0.30. I've tried to change the value but stays at 0.30

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-22 by esimanor

> Luminance seems to be anchored at 0.30. I've tried to change the 
value but stays at 0.30
>

Thanks for all this

Do we know what unit is being used for luminance (0.30 for blacks)? How 
does it relate to grey scale?

How do you set your brightness and contrast screen adjustments before 
starting calibration procedure?

Re: [colorvision_group] 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-22 by CDTobie@aol.com


In a message dated 4/22/06 8:44:39 AM, esimanor@... writes:


1.Do you know if one could possibly update software at later stage from
Spyder Express to say Syder 2 Suite or even Spyder pro since it seems
as if all use the same spyder device?


Yes, upgrades are available direct from ColorVision.

2.Can one select "Native" gamma and white point temperature using
Spyder 2 Suite or spyder Pro software/


Not native gamma, as a monitor's response curve is not likely to even be gamma shaped (let alone balanced channel to channel), and needs adjustment. But yes, native whitepoint can be selected in Spyder2 and Spyder2PRO.

3.can one manually select his own white and black point luminance
settings in the calibartion process using Spyder express? what about
spyder Pro?

Yes, one can define target white and black luminance values in Spyder2PRO (assuming your monitor has controls to adjust these functions) and use the Spyder and software to tune to those values. Express does not do this, though you can preset your B&W choices in advance of using Express, to whatever you choose.

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

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-22 by CDTobie@aol.com


In a message dated 4/22/06 10:39:03 AM, jvlist@... writes:


> 3.can one manually select his own white and black point luminance
> settings in the calibartion process using Spyder express? what about
> spyder Pro?

With the Spyder2PRO manually inputing White Luminance values works fine...but the Black
Luminance seems to be anchored at 0.30. I've tried to change the value but stays at 0.30


Its adjustable: try raising it. You can't set it lower than the native black of your monitor, which may be what had you stumped.

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

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-22 by CDTobie@aol.com


In a message dated 4/22/06 11:01:42 AM, esimanor@... writes:



Do we know what unit is being used for luminance (0.30 for blacks)? How
does it relate to grey scale?


This is in the standard luminance units of Candelas per square meter.

How do you set your brightness and contrast screen adjustments before
starting calibration procedure?

You are told to set them to factory defaults; if you don't have a reset control, I would recommend 50 percent contrast and 100 percent brightness as starting values.

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

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-23 by John Vitollo

> > the Black Luminance seems to be anchored at 0.30. I've tried to
> >  change the value but stays at 0.30

>  Its adjustable: try raising it. You can't set it lower than the native black 
> of your monitor, which may be what had you stumped. 
> C. David Tobie

I tried going higher to 0.40 and lower to 0.20...but value sticks at 0.30. 

I can set White Luminance with no problem.

Using Spyder2PRO Version 2.2-4

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-23 by esimanor

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
> You are told to set them to factory defaults; if you don't have a 
reset 
> control, I would recommend 50 percent contrast and 100 percent 
brightness as 
> starting values.

Thanks a lot for all that.

But here is a crucial issue, I think:

i am glad to read that there is such a thing as a standard luminance 
unit (candela). But how on earth do your Brightness and Contrast 
adjustments on your screen relate to this?? Is there any clear 
corellation between 1% change in Brightness and the increase of your 
black point by such and such candelas?! what about contrast?

Plus here is another critical point: what exactly is your Brightness 
and your Contrast adjustment knobs doing to your black and white 
point on an LCD screen? I read somewhere that an LCD can only offer 
one adjustment, which is the backlight of the display (most likely to 
affect only your black level (brightness?), I would have thought)?...

Now, the factory settings on my LCD (NEC multisync 1980 FXi) are 
as assumed Brightness: 100% and Contrast: 50% but this gives a very 
high black level indeed (too high )! Plus, i work with agencies in 
europe to whom I send processed files. most of these agencies still 
use CRT's which tend to be naturaly "darker" than LCD's. Could i 
possibly ask them to measure the luminance of there black and white 
point and try to "copy" them on my screen before calibrating? how 
would i go about this? Ideally they would provide me with a measure 
in candela for each point and i would feed it to my software, or I 
would be able to establish a corellation between the candela values 
and my settings?...

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-23 by CDTobie@aol.com


In a message dated 4/23/06 10:25:06 AM, esimanor@... writes:


i am glad to read that there is such a thing as a standard luminance
unit (candela). But how on earth do your Brightness and Contrast
adjustments on your screen relate to this?? Is there any clear
corellation between 1% change in Brightness and the increase of your
black point by such and such candelas?! what about contrast?


Does it matter? You adjust the controls, the Spyder reads the results. When you have gotten as close as your controls can manage, you stop tweaking, and move on.

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

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-23 by esimanor

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
> Does it matter? 

Does it matter to adjust your gamma and your white point temperature 
to given values? just tweak them until the result seems pleasing to 
your eyes and that's it...

but if you want to get any close to see your files on your screen 
more or less as your client will see them on his screen (provided you 
work with more or less the same ambiant light, which can be 
achieved), with similar shadows, mid tones and highlights, then you 
need to achieve similar luminance display target. Or does that not 
make any sense?


You adjust the controls, the Spyder reads the results. When 
> you have gotten as close 

Close to WHAT?


as your controls can manage, you stop tweaking, and 
Show quoted textHide quoted text
> move on.
> 
> C. David Tobie
> Product Technology Manager
> ColorVision Business Division
> DataColor Inc.
> CDTobie@...
> www.colorvision.com
>

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-23 by CDTobie@aol.com


In a message dated 4/23/06 11:49:45 AM, esimanor@... writes:


--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
> Does it matter?

Does it matter to adjust your gamma and your white point temperature
to given values?


Yes, if you wish to be calibrated to specific standards...


just tweak them until the result seems pleasing to
your eyes and that's it...


If pleasing is all that you need...

but if you want to get any close to see your files on your screen
more or less as your client will see them on his screen (provided you
work with more or less the same ambiant light, which can be
achieved), with similar shadows, mid tones and highlights, then you
need to achieve similar luminance display target. Or does that not
make any sense?


It does when you use Spyder2PRO to adjust your Whitepoint (the color of white). But your black luminance really has to do with what your monitor can manage, and your white luminance should really be set to relate to your ambient light. Unless you are running monitors side by side, its not necessary to set these to a predefined standard.


You adjust the controls, the Spyder reads the results. When
> you have gotten as close

Close to WHAT?


To the target values you specified when you began. If your target black luminance is set to .4, then the software will assist you in adjusting to that. Of course, if your monitor's native blackpoitn is .6, and you chose .4 because it sounded better to you, there is no way you will be able to lower the blackpoint, so you will fail to reach that target, just as asking for a black darker than what your printer, inks, and paper can manage is not possible.

For white, I would recommend you use the ambient light function of Spyder2PRO v2.2, and choose an appropriate white luminance value for your situation, instead of simply running your monitor at max luminance, which may be way off for your lighting (causing poor matching), not to mention burning your monitor out faster than necessary. White is very relative (as the eye is very adjustable), and unless monitors are side by side, setting them to the same white luminance is not necessary (or desirable), while setting them to appropriate white luminance for your environment is very necessary.


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

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-23 by esimanor

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
> To the target values you specified when you began. If your target 
black 
> luminance is set to .4, then the software will assist you in 
adjusting to that. Of 
> course, if your monitor's native blackpoitn is .6, and you chose .4 
because it 
> sounded better to you, there is no way you will be able to lower 
the 
> blackpoint, so you will fail to reach that target, just as asking 
for a black darker 
> than what your printer, inks, and paper can manage is not possible.
> 
> For white, I would recommend you use the ambient light function of 
Spyder2PRO 
> v2.2, and choose an appropriate white luminance value for your 
situation, 
> instead of simply running your monitor at max luminance, which may 
be way off for 
> your lighting (causing poor matching), not to mention burning your 
monitor 
> out faster than necessary. White is very relative (as the eye is 
very 
> adjustable), and unless monitors are side by side, setting them to 
the same white 
> luminance is not necessary (or desirable), while setting them to 
appropriate white 
> luminance for your environment is very necessary.

All this makes perfect sens, thank you
I wonder, though, if using your eye, under ambiant light, to 
determine the "right" black and white point luminances isn't even 
better than using software since these are such subjective notions. 
But then again: the two "knobs" available on most LCD screens 
(brightness and contrast) are not readily helpful for that... Not 
clear neither on which kind of chart this should be done.

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-24 by Brian Smith

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> 
wrote:

> 
> But here is a crucial issue, I think:
> 
> i am glad to read that there is such a thing as a standard luminance 
> unit (candela). But how on earth do your Brightness and Contrast 
> adjustments on your screen relate to this?? Is there any clear 
> corellation between 1% change in Brightness and the increase of your 
> black point by such and such candelas?! what about contrast?
> 
> Plus here is another critical point: what exactly is your Brightness 
> and your Contrast adjustment knobs doing to your black and white 
> point on an LCD screen? I read somewhere that an LCD can only offer 
> one adjustment, which is the backlight of the display (most likely 
to 
> affect only your black level (brightness?), I would have thought)?.
..
> 
> Now, the factory settings on my LCD (NEC multisync 1980 FXi) are 
> as assumed Brightness: 100% and Contrast: 50% but this gives a very 
> high black level indeed (too high )! Plus, i work with agencies in 
> europe to whom I send processed files. most of these agencies still 
> use CRT's which tend to be naturaly "darker" than LCD's. Could i 
> possibly ask them to measure the luminance of there black and white 
> point and try to "copy" them on my screen before calibrating? how 
> would i go about this? Ideally they would provide me with a measure 
> in candela for each point and i would feed it to my software, or I 
> would be able to establish a corellation between the candela values 
> and my settings?...
>
I may be completely wrong here but I think you are getting the wrong 
end of the stick about the purpose of this device. I don't think it is 
ever intended to match the illumination levels between monitors or any 
other viewing system, just give the same appearance of colour. Also I 
think you have the terms a little mixed up. My understanding of 
brightness, as a control, is that it adds or subtracts a constant 
value from the value of each pixel but the overall luminance of a 
pixel depends on the source of the light, be it backlight, CRT 
phosphor, or 10kW projector lamp. Contrast, as a control, affects the 
steepness of the curve that relates pixel values to screen brightness 
values. It should not affect the black or white point.

Again, I may be completely wrong, but I think it is unreasonable to 
expect to match the actual illumination levels of your monitor and 
your client's. All you can expect to do is both be able to see the 
same shadow and highlight detail and perceive the same colours. 
Presumably your client's screen is not the end use for your images. If 
they are going to be ending up as print then the illumination levels 
are meaningless anyway.

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-24 by CDTobie@aol.com


In a message dated 4/24/06 4:55:29 PM, zen1@... writes:


Again, I may be completely wrong, but I think it is unreasonable to
expect to match the actual illumination levels of your monitor and
your client's.


This is correct. You certainly cannot type the lower black values feom a CRT into the dialog for an LCD, and expect it to magically make your LCD blacker that its capable of being. However, the LCD, at a higher white luminance, higher black luminance, and higher ambient light level, can show the same number of levels, in a manner similar to the human eye, to what the CRT shows. Its all proportional; luminance is not absolute with the human eye.

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

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-24 by CDTobie@aol.com


In a message dated 4/22/06 10:29:29 PM, jvlist@... writes:


> > the Black Luminance seems to be anchored at 0.30. I've tried to
> > change the value but stays at 0.30

> Its adjustable: try raising it. You can't set it lower than the native black
> of your monitor, which may be what had you stumped.
> C. David Tobie

I tried going higher to 0.40 and lower to 0.20...but value sticks at 0.30.

I can set White Luminance with no problem.

Using Spyder2PRO Version 2.2-4


I just ran this app, and when I defined a new target, it offered me blank values for both white and black luminance, though it would fill them in later for me if I left them blank. At what point are you expecting to be able to change them, that you can't? I suspect this is not a bug, but a user expectation issue...

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

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-25 by John Vitollo

>I just ran this app, and when I defined a new target, it offered me blank values for both 
white and black luminance

If I define a new target the values are filled with the current settings. I then change both 
values and the new White Luminance value is updated in the "Current Settings" window but 
the Black Luminance value goes back to 0.30.

Same if I try to change the current settings using "Change these settings" and click 
through the Next button.... 

Thanks!

Using Spyder2PRO Version 2.2-4 Mac 10.4.6


On 4/24/06 7:54 PM, "CDTobie@..." <CDTobie@...> wrote:


In a message dated 4/22/06 10:29:29 PM, jvlist@... writes:

I tried going higher to 0.40 and lower to 0.20...but value sticks at 0.30.

I can set White Luminance with no problem.

Using Spyder2PRO Version 2.2-4


I just ran this app, and when I defined a new target, it offered me blank values for both 
white and black luminance, though it would fill them in later for me if I left them blank. At 
what point are you expecting to be able to change them, that you can't? I suspect this is 
not a bug, but a user expectation issue...

C. David Tobie

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-25 by CDTobie@aol.com


In a message dated 4/24/06 8:26:22 PM, jvlist@... writes:


If I define a new target the values are filled with the current settings. I then change both
values and the new White Luminance value is updated in the "Current Settings" window but
the Black Luminance value goes back to 0.30.

Same if I try to change the current settings using "Change these settings" and click
through the Next button....

Thanks!

Using Spyder2PRO Version 2.2-4 Mac 10.4.6

It sounds like this may be a beta version you are using? If so, please download the S2P v2.2 final release from the ColorVision.com website, and see if the issue still occurs.

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

www.colorvision.com

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-25 by esimanor

--- In colorvision_group@yahoogroups.com, "Brian Smith" <zen1@...> 
wrote:
> I may be completely wrong here but I think you are getting the 
wrong 
> end of the stick about the purpose of this device. I don't think it 
is 
> ever intended to match the illumination levels between monitors or 
any 
> other viewing system, just give the same appearance of colour. Also 
I 
> think you have the terms a little mixed up. My understanding of 
> brightness, as a control, is that it adds or subtracts a constant 
> value from the value of each pixel but the overall luminance of a 
> pixel depends on the source of the light, be it backlight, CRT 
> phosphor, or 10kW projector lamp. Contrast, as a control, affects 
the 
> steepness of the curve that relates pixel values to screen 
brightness 
> values. It should not affect the black or white point.

If contrast was to control that curve then it should be called Gamma, 
really.... no?
The terms brightness and contrast are confusing, even more when they 
relate to an LCD display. Strictly speaking and since the luminance 
of your display depends partly on your own subjective assesment and 
partly on the amount of ambiant light, these two "knobs" are there to 
allow you to set your pedestal (black level, usualy called 
brightness) and your white point luminance (usualy called contrast). 
This rule applies well on a CRT, as for LCD's I am not so sure.
  
> 
> Again, I may be completely wrong, but I think it is unreasonable to 
> expect to match the actual illumination levels of your monitor and 
> your client's. All you can expect to do is both be able to see the 
> same shadow and highlight detail and perceive the same colours. 

If you can adjust for same shadows and highlights and if you are set 
up for similar gamma, then you will see roughly the same thing, I am 
pretty sure.


> Presumably your client's screen is not the end use for your images. 
If 
> they are going to be ending up as print then the illumination 
levels 
> are meaningless anyway.

Well this is true but if you adjust your pictures for a screen whose 
over all luminance is widely different from the one on which your 
pictures will be seen then your pictures will appear widely too 
bright or dark on that same display, which indeed does not imply 
anything as for further uses. 
>

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-25 by Brian Smith

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> 
wrote:

> 
> If contrast was to control that curve then it should be called 
Gamma, 
> really.... no?
> The terms brightness and contrast are confusing, even more when they 
> relate to an LCD display. Strictly speaking and since the luminance 
> of your display depends partly on your own subjective assesment and 
> partly on the amount of ambiant light, these two "knobs" are there 
to 
> allow you to set your pedestal (black level, usualy called 
> brightness) and your white point luminance (usualy called contrast). 
> This rule applies well on a CRT, as for LCD's I am not so sure.

In truth I am right and you are partly right. When adjusting the 
contrast of a photographic image you adjust the centre of an S curve 
but the curve in question, the contrast on a CRT or LCD, is a straight 
line and so adjusting the contrast of an image with a fixed black 
point does indeed affect the luminance of white.

Contrast is definitely not gamma. Gamma is a curve that corrects 
linear digital images to account for the non linearity of visual 
perception. In fact the term I think originated in the compensation 
applied to the analogue video signal driving the grid of CRT's to 
correct for the non linear transfer function between grid voltage and 
anode current. This of course is long before the days of computer 
monitors.


> 
> > Presumably your client's screen is not the end use for your 
images. 
> If 
> > they are going to be ending up as print then the illumination 
> levels 
> > are meaningless anyway.
> 
> Well this is true but if you adjust your pictures for a screen whose 
> over all luminance is widely different from the one on which your 
> pictures will be seen then your pictures will appear widely too 
> bright or dark on that same display, which indeed does not imply 
> anything as for further uses. 

I don't believe that an observer is capable of making absolute 
luminance judgements. The contrast should be adjusted for the comfort 
of the viewer and to keep the CRT or LCD within it's linear range of 
reproduction. You may not realise it but if you try to drive your CRT 
too hard to get a bright picture in a room of high illumination 
current limiter circuits in the monitor will act to limit the 
brightness and protect the tube. When that happens it will affect the 
accuracy of the image.
All you should have to do in profiling your display is accurately 
reproduce colour and greyscale divisions and make sure that all 
gradations between black and maximum white are discernable. The Spyder 
can do that.

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-26 by esimanor

--- In colorvision_group@yahoogroups.com, "Brian Smith" <zen1@...> 
wrote:
> 
> Contrast is definitely not gamma. 

Oh Yes! Gamma and Contrast are intricately linked. Your display (any 
display) has got a native gamma that describes the way it is reacting 
to incoming signal. The software gamma that is applied to a signal 
supposed to be shown on that display is there to compensate for the 
non linear gamma curve of the display that would otherwise alter 
the "natural" contrasts of your picture

Now again, the confusion comes from the use of the wrong terminology 
for the two tweaking knobs on your display: "brightness" 
and "contrast". As said before, "brightness" relates to black level 
(and as such it will have a direct influence on the contrast of the 
picture). "Contrast" is brightning or darkening your white point 
hence it is having an influence on the overall brightness of the 
picture which shows the non sense in the choice of terminology...

  
> I don't believe that an observer is capable of making absolute 
> luminance judgements.

Of course not, since luminance judgement is subjective and varies 
from one viewer to the other and with ambiant light. Which is why I 
don't quite see the use of being able to set your black and white 
point luminance value in Candela unit in the Spyder Pro software 
version. How do these candela setting relates to the viewer assesment 
of display luminance?


>The contrast should be adjusted for the comfort

Yes but again, it is not the contrast that has to be adjusted for 
comfort, it is the pedestal and the white point luminance

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-26 by Tom

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> wrote:

> Of course not, since luminance judgement is subjective and varies 
> from one viewer to the other and with ambiant light. Which is why I 
> don't quite see the use of being able to set your black and white 
> point luminance value in Candela unit in the Spyder Pro software 
> version. How do these candela setting relates to the viewer assesment 
> of display luminance?

Its useful if you want to get side by side display units looking
exactly the same.

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-26 by esimanor

--- In colorvision_group@yahoogroups.com, "Tom" <ttrostel@...> wrote:

> How do these candela setting relates to the viewer assesment 
> > of display luminance?
> 
> Its useful if you want to get side by side display units looking
> exactly the same.


Yes but how does one know how to relate between a setting in Candela 
and the actual luminance level it will yield to the eye of the viewer? 
Plus how do you take into account the level of ambiant light if what 
you want is to achieve is respectively a given black and white point 
luminance?

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-26 by CDTobie@aol.com


In a message dated 4/26/06 10:09:04 AM, esimanor@... writes:



Yes but how does one know how to relate between a setting in Candela
and the actual luminance level it will yield to the eye of the viewer?
Plus how do you take into account the level of ambiant light if what
you want is to achieve is respectively a given black and white point
luminance?


Not to be flip, but by using the Ambient Light features of Spyder2PRO v 2.2...

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

www.colorvision.com

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-26 by Brian Smith

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> 
wrote:
>
> --- In colorvision_group@yahoogroups.com, "Brian Smith" <zen1@> 
> wrote:
> > 
> > Contrast is definitely not gamma. 
> 
> Oh Yes! Gamma and Contrast are intricately linked. Your display (any 
> display) has got a native gamma that describes the way it is 
reacting 

They may be linked but they adjust the response curve in different 
ways. Contrast is a purely linear adjustment.

> 
> Now again, the confusion comes from the use of the wrong terminology 
> for the two tweaking knobs on your display: "brightness" 
> and "contrast". As said before, "brightness" relates to black level 
> (and as such it will have a direct influence on the contrast of the 
> picture). "Contrast" is brightning or darkening your white point 
> hence it is having an influence on the overall brightness of the 
> picture which shows the non sense in the choice of terminology...

Contrast controls the linear component of the slope of the response 
curve of your display device it is not specifically a white point 
control. However, if you specify the black point (the start point of 
the response curve) using the brightness control then adjusting the  
slope with the contrast control must adjust the whitepoint within the 
limits of the device but it is not specificaly a whitepoint control.

> 
>   
> > I don't believe that an observer is capable of making absolute 
> > luminance judgements.
> 
> Of course not, since luminance judgement is subjective and varies 
> from one viewer to the other and with ambiant light. Which is why I 
> don't quite see the use of being able to set your black and white 
> point luminance value in Candela unit in the Spyder Pro software 
> version. How do these candela setting relates to the viewer 
assesment 
> of display luminance?

> Yes but again, it is not the contrast that has to be adjusted for 
> comfort, it is the pedestal and the white point luminance
>

First you say '"Contrast" is brightning or darkening your white point' 
and then you say, 'Yes but again, it is not the contrast that has to 
be adjusted for comfort, it is the pedestal and the white point 
luminance'.

Don't you think you are contradicting yourself there?

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ pro

2006-04-26 by esimanor

--- In colorvision_group@yahoogroups.com, "Brian Smith" <zen1@...> 
wrote:
 
> > Yes but again, it is not the contrast that has to be adjusted for 
> > comfort, it is the pedestal and the white point luminance
> >
> 
> First you say '"Contrast" is brightning or darkening your white 
point' 
> and then you say, 'Yes but again, it is not the contrast that has 
to 
> be adjusted for comfort, it is the pedestal and the white point 
> luminance'.
> 
> Don't you think you are contradicting yourself there?

No. The confusion comes from the wrong use of terminology when it 
comes to display tweaking knobs, as I tried to point out. When I 
refer to "contrast", I mean the knob called contrast on the display. 
when i refer to contrast without the ", I refer to the contrast of a 
picture, which is the real thing. I still maintain that when a 
display refers to "contrast" as a mean of adjusting your viewing 
device, it really means white point luminance level (rather 
brightness but certainly not contrast). at least that's what it was 
for a CRT. As pointed out earlier, i am not quite sure on LCD's. 
Of course, when you tweak your white point luminance with respect to 
your black level, it will have a marginal effect on the overall 
contrast of the picture since you will expand or reduce the span of 
your grey scale. But this is not like applying a gamma or an s 
curve....

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-26 by Tom

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> wrote:

> Yes but how does one know how to relate between a setting in Candela 
> and the actual luminance level it will yield to the eye of the viewer? 
> Plus how do you take into account the level of ambiant light if what 
> you want is to achieve is respectively a given black and white point 
> luminance?
>

Thats a very good question.  The answer is you need to use a color
appearance model.  These models predict observed luminance and hue
based on multiple environmental factors.  One of the current
reasonably accurate color appearance models is given the name CIECAM02.  

First lets define two terms.  These terms are "Brightness" and
"Lightness".  As seen in "Color Appearance Models" by Mark Fairchild
these are defined as follows:
-------------------------------------------
Brightness
Attribute of a visual sensation according to which an area appears to
emit more or less light.

Lightness
The brightness of an area judged relative to the brightness of a
similarly illuminated area that appears to be white or highly
transmitting.

Note
Only related colors exhibit lightness.

The definitions of brightness and lightness are straightforward and
rather intuitive. The important distinction is that brightness refers
to the absolute level of the perception while lightness can be thought
of as relative brightness — normalized for changes in the illumination
and viewing conditions.
---------------------------------------------

One nasty twist of color vision is that using pure candela of a color
is insufficient to determine the relative lightness of two samples
given the same viewing conditions.

When you are asking about luminance level ... do you mean lightness or
brightness?

Tom

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-26 by esimanor

--- In colorvision_group@yahoogroups.com, "Tom" <ttrostel@...> wrote:

> 
> One nasty twist of color vision is that using pure candela of a color
> is insufficient to determine the relative lightness of two samples
> given the same viewing conditions.
> 
> When you are asking about luminance level ... do you mean lightness or
> brightness?
> 
> Tom


This might be getting a touch too delicate for me. 
My concern is that i would like to think that me and my clients are 
seeing roughly "the same thing" when they look at my files...
I think that I can instinctively grasp the concept of color vision and 
lightness versus brightness but how does this come into play when using 
a calibration gear with a software only allowing you to set your own 
black and white point in candela unit? Plus again, how does all this 
relate to your display adjustment knobs?

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by CDTobie@aol.com


In a message dated 4/26/06 4:03:49 PM, esimanor@... writes:


This might be getting a touch too delicate for me.

Yes, Tom is an enthusiastic theorist, so what he's saying is both interesting and true, but probably not applicable on a practical level...

My concern is that i would like to think that me and my clients are
seeing roughly "the same thing" when they look at my files...


Agreed....

I think that I can instinctively grasp the concept of color vision and
lightness versus brightness but how does this come into play when using
a calibration gear with a software only allowing you to set your own
black and white point in candela unit? Plus again, how does all this
relate to your display adjustment knobs?

Here's the scoop. If you run an LCD at a relatively high candela value for White Luminance, in a relatively light room, it will look (relatively speaking) the same as a much dimmer CRT, with much dimmer ambient light (and a warmer white balance as well, due to another variable in the eye). The Ambient Light functions measure your room lighting, and define WhitePoint and White Luminance target values that will make for this relative match, and the hardware controls are used to reach these defined monitor target values. Is that clear enough?

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

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by esimanor

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
 > Here's the scoop. If you run an LCD at a relatively high candela 
value for 
> White Luminance, in a relatively light room, it will look 
(relatively speaking) 
> the same as a much dimmer CRT, with much dimmer ambient light (and 
a warmer 
> white balance as well, due to another variable in the eye). The 
Ambient Light 
> functions measure your room lighting, and define WhitePoint and 
White Luminance 
> target values that will make for this relative match, and the 
hardware 
> controls are used to reach these defined monitor target values. Is 
that clear enough?

Well, not quite I am afraid...
Ambiant light is less of a problem for me since I am in control of my 
work environment and my clients claim that they are too.
But what do you call hardware controls? are these "brightness" 
and "contrast" on your display? in which case we are back to square 
one: what are the corellations and what is the purpoe of being able 
to fix your black and white point in candela units through software?

have you checked the software update issue with customer support ?

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by CDTobie@aol.com

In a message dated 4/27/06 2:37:21 AM, esimanor@... writes:


> Well, not quite I am afraid...
> Ambiant light is less of a problem for me since I am in control of my
> work environment and my clients claim that they are too.
> 
Yes,   but I often find this claim backed up, these days, with a very dark 
room with a high luminance LCD in it, creating glare, and inappropriate viewing 
conditions, or conversely, someone using a CRT under what THEY consider dim 
light, meaning not full US office lighting, but still way above what a CRT can 
be used for color work under...

> But what do you call hardware controls? are these "brightness"
> and "contrast" on your display?
> 
Correct...

>  in which case we are back to square
> one: what are the corellations and what is the purpoe of being able
> to fix your black and white point in candela units through software?
> 
Correlations   to what, through what? The black luminance is monitor black, 
unless you choose to compromise that to the weakest black of a group of 
monitors, for exact side to side matching, and the whitepoint and white luminance are 
from the ambient target, and these candela values are reached by manipulating 
the hardware controls (front panel controls on most monitors). But I believe 
I've already said that, so I suspect there is a discontinuity between what I'm 
saying and what you're asking.

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

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by Tom

--- In colorvision_group@yahoogroups.com, "Brian Smith" <zen1@...> wrote:
>
> --- In colorvision_group@yahoogroups.com, "Tom" <ttrostel@> wrote:
> 
> > When you are asking about luminance level ... do you mean lightness 
> >or brightness?
> 
>  I get the impression esimanor may actually mean luminance as measured 
> in cd/sq m which is not a subjective thing.
>

Though he mentioned "to the eye of the observer" which depends
directly on the observation conditions.

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by CDTobie@aol.com


In a message dated 4/27/06 2:37:21 AM, esimanor@... writes:


have you checked the software update issue with customer support ?

Upgrades from Spyder2 to Spyder2PRO direct from ColorVision are $99US. Upgrade options and pricing from Spyder2express, the new kid on the block, have not been announced yet, and could conceivably effect the Spyder2 to Spyder2PRO upgrade pricing, when they come out...

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

www.colorvision.com

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by Tom

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:

> Yes, Tom is an enthusiastic theorist, so what he's saying is both
interesting 
> and true, but probably not applicable on a practical level...
> 


Bad habbit.  Its disturbing when only the "how" of a process has been
explained to me.  Knowing "why" always completes the picture and makes
it much easier for me to do something .... like color management! 
Most of the color management stuff on the web gets close to explaining
but stops short and doesn't have enough examples.

This link was very nice however and cleared up a lot of my questions
early on.

http://www.cambridgeincolour.com/tutorials.htm

If everyone would help maybe we collectively could make a better page
explaining color management and the issues related to it.  Would that
be something everyone would like?

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by esimanor

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:

> Correlations   to what, through what? 

I ment correlation between the tweaking of the knobs (which are 
usually accounted for in %) and the value of the white target in 
candela unit which you are trying to reach.

>The black luminance is monitor black, 
> unless you choose to compromise that to the weakest black of a 
group of 
> monitors, for exact side to side matching, and the whitepoint and 
white luminance are 
> from the ambient target, and these candela values are reached by 
manipulating 
> the hardware controls (front panel controls on most monitors). 

OK, but how do you reach a specific candela value while tweaking your 
knobs? Does CV spyder give you a measurement of black and white point 
as you tweak or do you need an extra piece of gear specificaly aimed 
at measuring a display luminance in candela which you would stick in 
front of your screen while having a white chart and then tweak which 
ever knob until you get to the right setting? How would you then take 
ambiant light into account?

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by esimanor

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:

> Upgrade options and pricing from Spyder2express, the new kid on the 
block, have not 
> been announced yet, and could conceivably effect the Spyder2 to 
Spyder2PRO 
> upgrade pricing, when they come out...

Spyder2Express is the one I just ordered. Any idea of when it will be 
possible to get hold of the software update? Is that going to be a site 
download?

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by CDTobie@aol.com


In a message dated 4/27/06 12:11:47 PM, esimanor@... writes:


OK, but how do you reach a specific candela value while tweaking your
knobs?


There is a bar, with an ideal point at the center and your current value shown on the bar. You push the appropriate control to go in the right direction, until you go a notch too far, then you toggle a bit to see what exact setting best centers the bar. The finer the increments of your control, the more exacting your match can be. But close is close enough.

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

www.colorvision.com

Re: [colorvision_group] Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by CDTobie@aol.com


In a message dated 4/27/06 12:15:30 PM, esimanor@... writes:



Spyder2Express is the one I just ordered. Any idea of when it will be
possible to get hold of the software update? Is that going to be a site
download?


Are you referring to a incremental update, or to a paid upgrade to Spyder2 or Spyder2PRO? If its the latter, then the details should be announced next week. If its the former, the latest version of express is already available on our European site and will be on our US site after the current site upgrade is completed.

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

www.colorvision.com

Re: 3 questions concerning calibration procedures with spyder express/ 2suite/ p

2006-04-27 by esimanor

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
> Are you referring to a incremental update, or to a paid upgrade to 
Spyder2 or 
> Spyder2PRO? If its the latter, then the details should be announced 
next 
> week. If its the former, the latest version of express is already 
available on our 
> European site <www.colorvision.ch> and will be on our US site after 
the 
> current site upgrade is completed.


Thanks. I will first want to upgrade to latest express version but 
later on i might well upgrade to 2suite or 2pro (depending on pricing)

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