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peter 04-12-2005 05:08 AM

color calibration question
 
I understand that uncalibrated CRT monitors has approximately the sRGB
profile, that's why digital cameras all have sRGB profile as default.

What happens after the monitor is calibrated using those spyder calibration
device and the color profile loaded into windows? Does it now have a perfect
sRGB profile (which has a gamma of 2.2), or does it now have gamma of 1.0
(perfectly linear)?

I'm hoping it's the first case because that means all digital photos would
look correct on the monitor. If it's the 2nd case, that means all digital
photos would need to be converted to the gamma=1.0 color space before it
looks good on the monitor.



Bubbabob 04-12-2005 06:26 AM

Re: color calibration question
 
"peter" <nospam@nospam.com> wrote:

> I understand that uncalibrated CRT monitors has approximately the sRGB
> profile, that's why digital cameras all have sRGB profile as default.
>
> What happens after the monitor is calibrated using those spyder
> calibration device and the color profile loaded into windows? Does it
> now have a perfect sRGB profile (which has a gamma of 2.2), or does it
> now have gamma of 1.0 (perfectly linear)?
>
> I'm hoping it's the first case because that means all digital photos
> would look correct on the monitor. If it's the 2nd case, that means
> all digital photos would need to be converted to the gamma=1.0 color
> space before it looks good on the monitor.
>
>
>


2.2

sRGB is a working colorspace, not a monitor colorspace. It was designed
not to exceed the worst case gamut of about 40 different cheap monitors.
A good monitor, properly calibrated should have a considerably larger
gamut than sRGB. I recommend shooting and working in Adobe RGB 98 and
only converting to sRGB for web work (browsers are all designed for sRGB
gamuts) or if your printer expects an sRGB colorspace before the
printer's profile is applied. I profile my printers and design the
profiles to expect the larger gamut of Adobe RGB 98 as an input but most
factory printer profiles probably don't.

Roy 04-12-2005 09:17 AM

Re: color calibration question
 
"peter" <nospam@nospam.com> wrote in message
news:pJI6e.11310$H_5.9871@trnddc01...
>I understand that uncalibrated CRT monitors has approximately the sRGB
>profile, that's why digital cameras all have sRGB profile as default.
>
> What happens after the monitor is calibrated using those spyder
> calibration device and the color profile loaded into windows? Does it now
> have a perfect sRGB profile (which has a gamma of 2.2), or does it now
> have gamma of 1.0 (perfectly linear)?
>
> I'm hoping it's the first case because that means all digital photos would
> look correct on the monitor. If it's the 2nd case, that means all digital
> photos would need to be converted to the gamma=1.0 color space before it
> looks good on the monitor.
>



Uncalibrated Monitors do not approximate to the sRGB Profile. Just have a
good look next time you are in one of the discount warehouses, you should be
able to see that the monitor colours all look different. It is unfortunate
that the colour system, ( it is not a profile), used by monitors is called
RGB, hence the confusion.

Not all Cameras convert their output to sRGB, the better ones now include
Adobe RGB as an option.

sRGB, Adobe RGB, Pro-photo RGB, etc are all Working Space Profiles. They
define the numerical values associated with particular colurs and shades of
colours, and are used by Graphics Programs to do the calculations required.
sRGB has a narrower range of colour (Gamut) than Adobe, and Pro-photo has a
greater range.

A Monitor Profile is used by the Program to convert the numbers in the
Working Space Profile, so that the colours seem on the screen are accurate.
The idea is that, an image should look exactly the same no matter which
Calibrated Monitor it is being displayed on.

Printer Profiles are used by the Program to convert the numerical values, so
that the colours on the Print will be accurate. The idea is, again, that an
image should look the same, no matter which Calibrated Printer is used to
make the Print.

There are, of course, variations between the Ideal and Real Life.

Printer Profiles are for a Specific Printer, using Specific Inks and
Specific Paper.

Epson do supply profiles for their Printers, using Epson Inks and Epson
Papers, and so do other Printer companies. Kodak, Tetenal, Olmec, etc,
will supply Profiles for certain of their Papers, in Specific Epson & Canon,
etc, Printers using the Original Ink sets. These types of profiles are often
called "Canned" profiles, and are fairly accurate most of the time.

Colour Management is quite a difficult subject, and understanding is not
helped, by a lot of the half-baked advice you may receive from non experts.
"My camera works in sRGB, so I set my Printer to sRGB" is a common one.

Roy G









Paul Mitchum 04-12-2005 09:31 PM

Re: color calibration question
 
Bubbabob <rnorton@_remove_this_thuntek.net> wrote:

[..]
> sRGB is a working colorspace, not a monitor colorspace. It was designed
> not to exceed the worst case gamut of about 40 different cheap monitors. A
> good monitor, properly calibrated should have a considerably larger gamut
> than sRGB. I recommend shooting and working in Adobe RGB 98 and only
> converting to sRGB for web work (browsers are all designed for sRGB
> gamuts)


Just a nit with your parenthetical:

Many web browsers respect an embedded ICC profile, and many also respect
a ColorInfo rule in CSS (which lets you specify profile and intent). If
there's no profile and no CSS rule, some browsers will use sRGB and some
will use the monitor profile. sRGB is the safest, but additionally
embedding the profile and marking it up in the CSS is the safest of all.

Some info: <http://www.ekdahl.org/kurs/colormanage.htm>

David Dyer-Bennet 04-12-2005 11:15 PM

Re: color calibration question
 
Bubbabob <rnorton@_remove_this_thuntek.net> writes:

> "peter" <nospam@nospam.com> wrote:
>
>> I understand that uncalibrated CRT monitors has approximately the sRGB
>> profile, that's why digital cameras all have sRGB profile as default.
>>
>> What happens after the monitor is calibrated using those spyder
>> calibration device and the color profile loaded into windows? Does it
>> now have a perfect sRGB profile (which has a gamma of 2.2), or does it
>> now have gamma of 1.0 (perfectly linear)?
>>
>> I'm hoping it's the first case because that means all digital photos
>> would look correct on the monitor. If it's the 2nd case, that means
>> all digital photos would need to be converted to the gamma=1.0 color
>> space before it looks good on the monitor.
>>
>>
>>

>
> 2.2
>
> sRGB is a working colorspace, not a monitor colorspace. It was designed
> not to exceed the worst case gamut of about 40 different cheap monitors.
> A good monitor, properly calibrated should have a considerably larger
> gamut than sRGB. I recommend shooting and working in Adobe RGB 98 and
> only converting to sRGB for web work (browsers are all designed for sRGB
> gamuts) or if your printer expects an sRGB colorspace before the
> printer's profile is applied. I profile my printers and design the
> profiles to expect the larger gamut of Adobe RGB 98 as an input but most
> factory printer profiles probably don't.


However, most online photo-printing places I've looked at want you to
deliver to them in sRGB.
--
David Dyer-Bennet, <mailto:dd-b@dd-b.net>, <http://www.dd-b.net/dd-b/>
RKBA: <http://noguns-nomoney.com/> <http://www.dd-b.net/carry/>
Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/>
Dragaera/Steven Brust: <http://dragaera.info/>

David Dyer-Bennet 04-12-2005 11:16 PM

Re: color calibration question
 
"Roy" <royphoty@iona-guesthouse.co.uk> writes:

> "peter" <nospam@nospam.com> wrote in message
> news:pJI6e.11310$H_5.9871@trnddc01...
>>I understand that uncalibrated CRT monitors has approximately the sRGB
>>profile, that's why digital cameras all have sRGB profile as default.
>>
>> What happens after the monitor is calibrated using those spyder
>> calibration device and the color profile loaded into windows? Does it now
>> have a perfect sRGB profile (which has a gamma of 2.2), or does it now
>> have gamma of 1.0 (perfectly linear)?
>>
>> I'm hoping it's the first case because that means all digital photos would
>> look correct on the monitor. If it's the 2nd case, that means all digital
>> photos would need to be converted to the gamma=1.0 color space before it
>> looks good on the monitor.
>>

>
>
> Uncalibrated Monitors do not approximate to the sRGB Profile. Just have a
> good look next time you are in one of the discount warehouses, you should be
> able to see that the monitor colours all look different. It is unfortunate
> that the colour system, ( it is not a profile), used by monitors is called
> RGB, hence the confusion.


No, actually, sRGB *was* defined to approximate uncalibrated
monitors. That's why it's the recommended profile to convert images
for web display to, for example.
--
David Dyer-Bennet, <mailto:dd-b@dd-b.net>, <http://www.dd-b.net/dd-b/>
RKBA: <http://noguns-nomoney.com/> <http://www.dd-b.net/carry/>
Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/>
Dragaera/Steven Brust: <http://dragaera.info/>

Bubbabob 04-13-2005 04:44 AM

Re: color calibration question
 
usenet@mile23.c0m (Paul Mitchum) wrote:

> Many web browsers respect an embedded ICC profile, and many also respect
> a ColorInfo rule in CSS (which lets you specify profile and intent)


Name two; or even one that isn't Mac only.


papenfussDIESPAM@juneauDOTmeDOTvt.edu 04-13-2005 11:43 AM

Re: color calibration question
 
: > Uncalibrated Monitors do not approximate to the sRGB Profile. Just have a
: > good look next time you are in one of the discount warehouses, you should be
: > able to see that the monitor colours all look different. It is unfortunate
: > that the colour system, ( it is not a profile), used by monitors is called
: > RGB, hence the confusion.

: No, actually, sRGB *was* defined to approximate uncalibrated
: monitors. That's why it's the recommended profile to convert images
: for web display to, for example.
: --
IIRC, it was defined using D65 as the whitepoint. Probably 98% of the
monitors out there are currently set to their default white point of 9300K since
"brighter" displays sell better.

-Cory

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************


Roy 04-13-2005 02:28 PM

Re: color calibration question
 
<papenfussDIESPAM@juneauDOTmeDOTvt.edu> wrote in message
news:d3j0l9$r1e$1@solaris.cc.vt.edu...
>: > Uncalibrated Monitors do not approximate to the sRGB Profile. Just
>have a
> : > good look next time you are in one of the discount warehouses, you
> should be
> : > able to see that the monitor colours all look different. It is
> unfortunate
> : > that the colour system, ( it is not a profile), used by monitors is
> called
> : > RGB, hence the confusion.
>
> : No, actually, sRGB *was* defined to approximate uncalibrated
> : monitors. That's why it's the recommended profile to convert images
> : for web display to, for example.
> : --
> IIRC, it was defined using D65 as the whitepoint. Probably 98% of the
> monitors out there are currently set to their default white point of 9300K
> since
> "brighter" displays sell better.
>
> -Cory
>
> ************************************************** ***********************
> * Cory Papenfuss *
> * Electrical Engineering candidate Ph.D. graduate student *
> * Virginia Polytechnic Institute and State University *
> ************************************************** ***********************
>


Hi there.

Please lets not get too much into semantics, over this. As someone said
earlier, sRGB was designed with low end monitors in mind. But an
Uncalibrated monitor, still needs to be Calibrated, even if the Working
Space is going to be sRGB.

Because all Elephants are grey, does not mean that all grey things are
Elephants.

The OP seemed to under the impression that the Profile resulting from
Calibration would be a "perfect" sRGB Profile, when as we all know it will
be an "Output" type of Profile, and will be used to make Convertions from
whatever Working Space is chosen. I was a little concerned that he would
then fall into the trap of using his Calibrated Monitor Profile as a Working
Space. Hence my rather wordy, and not technically exact, explanation.

Roy G



David Chien 04-13-2005 09:10 PM

Re: color calibration question
 
For consumers, simply use sRGB all the way through. Most LCD panels
sold today have a sRGB mode. sRGB mostly comes out of digicams and
printers. and once you've set everything to work in sRGB, you'll be
surprised! -- instant color matching w/o spending a cent. (Okay, not
100% accurate, but pretty darn close.)

I found this to work the best for me after trying those $$ Spyders and
other color matching/calibration programs.

Why?

1) You'll NEVER EVER get a 100% matching between monitor and print. One
is transmissive, the other is reflective. It is PHYSICALLY IMPOSSIBLE
to make the match exactly -- it's like trying to make a light bulb
(monitor) match the print (printer). Just can't be done because the
print can't glow and shine light like the light bulb.

2) Even if you spend $$$$$ on the color calibration programs and tools,
#1 still is in effect. You will still find yourself annoyed to death
that the print doesn't look exactly like the monitor until you realize #1.

3) Everyone views prints under differing lighting conditions - this
alone will result in color mismatch between what you see on the print
vs. the monitor. You'll have to change out all of your light bulbs for
color standard bulbs if you want to see everything in a consistant way.
(and even here, depends on your choice of reference color temperature
- 5000k 5500k 6000k etc)

As a result of #1 through #3 AND the fact that the human eye's color
response varies minute-by-minute and day-to-day, you'll realize that
unless you're spot checking every print sample in multiple locations
with a color spectrometer to make sure every print is matching intended
colors exactly (or calibrating printers before), you'll notice that one
day, a print may look superb, but the next day, it's not so great.

Add to that the fact that inkjet photo prints (what most home users use)
significantly shift in color and density over the course of a week or
two after the print was made = people pulling hair like crazy. "But the
print looked great the moment it was printed!" they say! only to
discover that by week's end, it's totally different. (due to the
water-based inks drying over time, etc.)

---

The quick & easy way is to simply rely upon the sRGB standard most
makers have agreed upon. They've already calibrated their devices to
that, and like me, you can get pretty close (90% or so) to the true
colors by simply sticking with a sRGB pipeline.

Those that want more can always color manage, calibrate, etc. + change
their light bulbs, use color checkers, etc., but that's usually a very
time consumer and costly step to take knowing that no matter what,
prints won't look exactly the same as the monitor image.


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