isw <> wrote:
> In article <ptvoa9->,
> Wolfgang Weisselberg <> wrote:
>> isw <> wrote:
>>
>> > I'm still trying to find someone who actually *knows* in precisely what
>> > ways the Apple "eyeball" calibration method is flawed.
>>
>> I gave you the answer a couple posts ago.
>> Short form: 5 measurement points on the grey axis aren't enough
>> for many screens even *IF* the eye was a perfect instrument.
> The human eye is very good at making comparisons and determining when
> two things are the same
Within 1-2 ∆E typical. Consumer sensors are more accurate,
much faster and don't tire.
> -- which is the way the Apple method works.
So how do you compare to, say, a GretagMacbeth Colour Checker
(and that's only 24 patches, not hundreds) in D50 normlight (which
costs more than a simple tristimulus sensor) to your monitor?
So how do you compare the brighness to, say, 120 cd/m²?
How do you comare the chromaticity of the 100% white to the
neutral grey or white in D50 (or D65, or whatever you want to
standardize on)?
All you *can* compare is a relative brightness compared to 0% and
100% (i.e. you have no idea if your screen is too bright!) and
the gray neutrality *compared to* the overly blueish white of
the native monitor setting.
> Have you ever used it?
Does one have to use it *and* not compare the result with an
instrument to have a religious experience?
How about *you* use it and then measure, say, 800 odd patches and
tell us how close *you* came using the eyeball method on *your*
monitor?
>> So if your screen, on the average, is showing hard to tolerate
>> colour shifts and for some colours even completely different
>> colours ... then the calibration method is unusable.
> Or (as I suspect might be the case) the screen (and its driving
> hardware) is simply not able to be calibrated properly.
Yep, that's the "sour grapes" strategy.
Do rent a hardware puck for a couple days and tell us. Your
average photo club, your rental service, etc. all can supply
you with one.
> Using the Apple calibration method, I can do a perfectly decent job on
> the Dell 2407;
So, how high is the average ∆E, how bad the worst ∆E and
please show us an ∆E plot ...
Oh, you don't KNOW!
So how do you *know* you can do a perfectly decent job?
> all the test images on the web site you referred to look
> just fine.
Aha.
BTW, which web site did I refer to?
Oh, but I *didn't*.
So all the imaginary test images on an imaginary website look
'just fine', when you don't even have any idea how they're supposed
to look.
I am sure you didn't have them printed on well calibrated systems
(with enough gamut for the whole image) and compared to your
monitor under normlight.
> I cannot achieve similar performance from the MacBook's
> display, whether I use the Apple-provided profile, or one of my own --
> though the latter are (I think) somewhat better.
You're using very insufficient methods, which may work somewhat
on some displays, but which is not good enough for others.
That's like saying a 2 MPix compact camera doesn't resolve
enough for a 1 meter sized image viewed at close distrance,
THEREFORE it's impossible to create such an image at all.
> I have, on several occasions, tried to calibrate other LCD screens as
> well, also mostly with poor results. It is known that LCD screens show
> much more variability in color accuracy than CRTs (usually),
That's true. How could you have both wide gamut screens and
standard gamut screens otherwise?
> and that
> would seem to indicate that not all screens can be properly calibrated.
Ah ... no. Even systems like printers with 8, 10, 12 colours
can be calibrated --- and that even though they're mixing colours
wildly[1] and they're not exactly known to be monotonous.
So, it's easily true that Apple's eyeball method is not enough
for LCDs (and indeed I said as much), but THAT'S ALL.
> Otherwise, why would it even be mentioned in reviews?
Lots of things are mentioned in reviews.
And some monitors are better (!= good, they're much to bright!) as
they come from the factory than others.
>> > Because from my
>> > understanding of how it works, it should produce pretty decent results.
>> Decent as in 'the grey axis will look quite neutral to the
>> untrained eye, and the colours will be similar', yes.
> Well, the Dell 2407 is, and the MacBook is not, capable of producing a
> neutral grey scale; that is precisely the problem.
The MacBook is perfectly capable of producing a neutral grey
scale.
"After calibration the colour is neutral"
http://forums.whirlpool.net.au/archive/957785
It's your technique that's lacking.
> It cannot do that
> even at the five points that you claim are insufficient.
If you cannot set it to neutral grey because the adjustment
slider area is too small, then it is a fault of your technique.
If you cannot set it to neutral because the adjustment steps are
too large, then it is a fault of your technique.
If you cannot set it to neutral because youc cannot see what
neutral would be, that's again a fault of your technique.
> I have a
> feeling that if (as you claim) a hardware calibrator can manage to stick
> values in the LUT that the "eyeball" method cannot, the result would be
> better color accuracy at the expense of some other parameter, possibly
> brightness or contrast ratio.
That's true: if you need to convert your 9600K monitor white
to D50, you pay with some brightness. If you need to correct
your dark colours, you may need to raise the black point a bit.
Both eat contrast ratio.
Just like a not wide open aperture eats light.
> Given that choice I (and perhaps Apple)
> would choose a bright display.
Then STOP TRYING TO CALIBRATE DISPAYS INCLUDING APPLE'S
"EYEBALL" METHOD!
STOP USING ANY PROFILES!
STOP THIS WHOLE THREAD!
You want overly bright, blue-tinted displays, so that every
print looks too dark and too red? FINE. YOUR PROBLEM.
> After all, the Mac is a portable
> computer, not a dedicated photo editor; the screen needs to be usable
> under a wide range of situations.
Yep, that's why overly bright and overly blue is good. NOT!
Ever heard of being able to remove the settings from the LUT
and reverting to "default values"?
>> Decent as in 'If you hold your print next to your monitor it'll
>> look the same[1][2]', not in a 1000 years.
> FWIW, I'm not interested in hard-copy output; it really is pretty
> limited, both in gamut, and in contrast ratio as well.
Really. That must be because you love overly bright, overly
blue screens.
>> Decent as in 'The monitor will give you a good idea how the print
>> will look like', depends a lot on how good an idea you want.
>> If you've not got a good eye for colour and look at the print
>> a few minutes after you've seen the monitor and don't have any
>> comparisons when looking at the print (i.e. you're not trying to
>> hit a specific colour, say a company logo's colour or a specific
>> flower and thus are not holding the print next to such an object),
>> you will be OK.
>> > Your statements and questions above make it pretty clear that you're not
>> > going to be the one who provides the answer.
>> It seems you're not even getting that you have been handed facts.
>> Or at least that you have problems evaluating what they mean.
>> OR that you are a fanboi and therefore there are no arguments
>> that could make you change your mind, since that would challenge
>> a dogma or something.
> If I were a "fanboi", would I be talking about how good the Dell display is, and
> complaining about the one in the Mac?
You're a fanboi of the Apple eyeball method.
> I just want some facts, specifically explaining *how* the Apple method
> is flawed.
How many repetitions do you want?
> All you've done is to say over and over that the mechanized
> method is better. I want to know *why*.
- the eye isn't an absolute instrument. It cannot tell you if
the monitor is too bright or too blue (or too red) without
something to compare against.
- the eye is less sensitive to colour differences than an
instrument. If you use the measurements to extrapolate to other
colours, you need to be more exact ... the larger the range
of colours you extrapolate to, the more exact you need to be.
There are >16 million colours ...
- 5 measurements are about 50 too few --- and even then you
only have a minimal, rough profile.
- 5 measurements on the grey axis don't say anything about the
other colour axes nor about the rest of the colour space.
- 5 measurements (or 10, as it may be) only allow a gamma or a
shaper profile, and they have assumptions on the display that
said display doesn't necessary fulfill.
- Apple's eyeball method is based on relative brightnesses,
compared to 0% and 100% white. Said white is usually completely
wrong, as it leaves the factory. Connect the dots ...
- Apple's eyeball method isn't good enough for many LCDs, as you
have proven (MacBook screen!)
I guess I said all that a couple times now.
> Saying that "you get more, and
> more precise, numbers" doesn't mean anything unless you can state
> precisely *why* that difference matters.
"A color image which straddles the two screens can be a painful
thing to see ..."
-- isw in Message-ID: <isw-4ECE75.14125826052012@[216.168.3.50]>
It's rather obvious, isn't it?
All you need is 2 proper profiles, one for each monitor ... for
which you need more numbers to remove gamma curve assumptions and
the like and for which you want more precise numbers to have less
extrapolation errors. *Especially* for your laptop you need
many more measurements.
If you were living close enough, I'd come over and calibrate and
profile your screens just to prove my point.
So I can just tell you: rent or borrow a hardware unit and try
for yourself.
> It's like the audio folks who
> go on about 24 bit samples at 96 or 192 kilosamples/second, and how much
> "better" that is than 16 bit, 44.1 kilosample sound. Sure, the numbers
> are bigger, but in fact, the difference is simply not audible, so who
> cares?
Do you know what a brick filter is?
Do you know if it's easier to build if the steepness of the filter
can be reduced?
Do you know why a deep pass filter is needed for digital sampling?
Then you know why more samples/s.
Do you know why some people use RAWs with 12 or 14 or more bits
when JPEGs with visually evenly distributed 8 bit are visually
not different at all (and in fact almost all monitors can
only display 8 bit?)
Then you know why 24 bits sample depth is preferred for some
tasks.
Did you know that sometimes it's much easier to throw more
data into a system than to optimize it to the same result
with less data?
>> If it's the first two, feel free to ask "what does ΔE mean?"
>> or "How do you arrive at these ΔE numbers?" or similar.
> I have some knowledge of those, and a few other, things concerning color
> imaging. Prior to retiring, I spent many years in television technology
> including some work with very large screen projection systems, helped
> develop MPEG-2, and designed a few high-performance film printers, among
> other things.
OK. So it's more a case of obstinacy of old age: you think you
already know everything, so there could be no reason someone else
could realistically offer that would change your mind. I still
hope it's not the reason, but as they say, hope's the last thing
to die.
Please report back with the ∆E values of your 'calibrated'
screen.
Or at least tell us with your knowledge which 5 points I
should pick for calibrating my LCD monitor ...
-Wolfgang
[1] for example they're mixing additional CMY (and their light
versions) to the black (and grey and light grey) inks to
reduce speckle (just one or two black or grey dots look more
irregular than a whole handful of dithered LM, LC and Y dots)
and black is even blacker if CMY is mixed into it as well.
Oh, and of course there's no perfectly neutral grey, so there
CMY (or their light versions) needs to be mixed in, too.