[Scribus] [SLIGHTLY OFFTOPIC] How do I do color correction

[jon]

Am 06.03.2007 um 22:44 schrieb Hal V. Engel:

> On Tuesday 06 March 2007 10:11, Dwain Alford wrote:
>> i have been mystified by color management for years.  all of this  
>> profiling
>> for different papers, inks, printers.  well at last i have come  
>> upon a
>> system that works for me and it didn't cost any money profiling any
>> hardware of for paper.
>>
>> most non postscript printers render i rgb, regardless of how many ink
>> cartridges you have to install.  all of this monitor calibration i  
>> have
>> found is bunk as well.  and as for paper, well, i use what ever i  
>> want and
>> still get a good print with the expected results of ink absorption  
>> with
>> certain papers and the finish of the paper (read: photo).
>>
>> i have an epson stylus photo 1200.  it has a black cartridge and a  
>> 6 color
>> color cartridge.
>
> The 1200 series has 6 inks total including the black cart not  
> seven.  Probably
> a typo.
>
>> i have fought with getting what is on the screen to the
>> paper since i have had it, but i finally figured it out.
>>
>> now i am on a windows os, so your installed profiles may be  
>> different, but
>> i do believe that the srgb color space (same as srgb iec61966-2.1) is
>> available on all operating systems.  one other note, kodak and hp  
>> offer a
>> srgb iec61966-2.1.  in fact, on my system, the srgb color space  
>> profile is
>> from hp and the srgb profile is from kodak to be used in a d65  
>> monitor set
>> up with a gama of roughly 1.8.
>
> sRGB is an approximation of a monitor calibrated to gamma 2.2 and  
> D65.  Not
> gamma 1.8 which is a now long obsolete Mac standard.  In addition,  
> most CRTs
> have a native gamma between 2.3 and 2.5 so even sRGB will be  
> incorrect for
> most CRTs.

Sorry to intervene here but I thought gamma 1.8 is a defacto standard  
for prepress monitor devices, isn't it?



>> when available i set my graphics software (all of them) to srgb
>> iec61966-2.1for the rgb color space.  i use the swop v2 setting for
>> cmyk (this setting
>> depends on the color profile of your commercial printer, match it and
>> you're in heaven, nirvana, elysian fields or any other good place  
>> you want
>> to be). inkscape uses a flavor of srgb iec61999-2.1.
>>
>> now for the hardware.  i set my printer to the srgb color space  
>> profile.
>
> As you point out above you are on Windows.  On Windows the system  
> default
> color space is sRGB and all devices (printer, video...) using the  
> default
> driver settings are supposed to be sRGB.  This of course is not  
> always the
> case (in fact it seldom is) and users who understand color  
> management do not
> use the default driver settings for printing in their color managed  
> work
> flows.  Why? Because in the default mode the drivers do all sorts of
> automatic stuff that make them unsuited to a color managed work  
> flow.  That
> is the results are unpredictable unless all of the automatic  
> trickery is
> turned off.
>
> If you go to the Epson download site you can get a set of profiles  
> for many of
> the Epson printers including the 1280/1290, R2400, R1800,  
> R800.....  I don't
> know about the 1200 but you might want to check.   In addition  
> there is a
> manual that is part of the download that describes how to use these  
> profiles.
> That manual says to use the no color correction mode (IE. turn off  
> all of the
> automatic stuff) when using the supplied profiles.  In addition the  
> manual
> has very detailed instructions on all of the settings to be used in  
> the
> driver with the profiles.  These profiles are paper and printer  
> specific and
> are only valid with the specific Epson papers used to create the  
> profiles.
> These are Epson's directions on how to make color management work  
> with their
> printers not mine.  So please have a look.
>
> One other thing to point out is that even though modern ink jet  
> printers like
> the Epson 1280 and R2400 have a limited somewhat smallish gamut the  
> gamuts of
> these devices have a significantly different shape than the sRGB  
> gamut and
> there is are significant parts of the gamuts of these devices that  
> fall
> outside of what can be represented by sRGB (yellows are the worst  
> case).
> That is you will be getting either clipping of what would otherwise  
> be usable
> colors or you will be incorrectly printing some colors if you treat  
> these
> devices as sRGB devices.    The gamuts of these printers are also
> significantly larger than your typical offset printer so profiles like
> ISOCoated are not correct for these devices either.
>
>> now you can go to http://www.color.org and down load icc  
>> profiles.  there
>> you will find the srgb profile mentioned above one with and one  
>> without
>> black point settings.  read the difference between the two.  i  
>> have used
>> them both, but for the hardware i have i stick with the srgb color  
>> space
>> profile.
>>
>> my microtek 5900 scanner is set to srgb iec6199-2.1
>
> Why?  It is easy and inexpensive to create custom profiles for your  
> scanners
> and cameras.  For flat bed scanners all you need is an ($15 +  
> shipping)
> IT8.7/2 target from Wolf Faust, LProf or ArgyllCMS (Lprof is easier  
> to use
> and both are open source and free), and a few minutes to scan the  
> IT8/7.2
> target and process it into a high quality custom profile.  Both  
> pieces of
> software will create world class input device profiles.  If  
> correctly created
> these custom profiles will definitely be better than using sRGB for  
> your
> scanner.  As an example raw processed images from my DSLR have a  
> gamut that
> is almost twice as large as sRGB at almost 70% of CIELab.  There is  
> no way
> that I could use sRGB for this device and not either loose (clip) or
> misrepresent almost half of the devices available gamut.  I should  
> also point
> out that the IT8.7/2 target itself actually has a gamut that is  
> larger than
> the sRGB gamut and most scanners will be able to capture the full  
> gamut of
> the target.
>
>> and so is my monitor,
>> but the colors are sometimes off, what to do, what to do?
>>
>> here comes the tricky part, the monitor settings.  i have seen  
>> them all.
>> some go to yellow side (d50) and some go to the blue (d93); but as  
>> for me,
>> i want a neutral setup.  i took the chance one day and did the user
>> settings to adjust my monitor.
>>
>> now i come from a photographic background and understand a little  
>> about
>> color and color correction.  since i wanted a neutral setup that  
>> would
>> render a print as close to what i had on my monitor i had to make my
>> monitor neutral, thus the need for the user defined color settings.
>>
>> i took a deep breath and set the r,g & b to 50%, and made a  
>> print.  now
>> remember all of my software and hardware carry the same srgb and  
>> cmyk color
>> profiles.  when i viewed the print, it was like a miracle, but it  
>> didn't
>> match my monitor.  the print was lighter than my monitor.  i saw  
>> all of the
>> detail and color that i was supposed to, the brightness and  
>> contrast in the
>> print was where i wanted it, but it didn't match my monitor.  so i  
>> turned
>> up the brightness on my monitor to match, as closely as possible, the
>> density of the print.
>>
>> viola!  i was in synch hardware and software wise for the first  
>> time since
>> 1999.  but did it really work outside my environment?  i write a  
>> basic
>> computer skill column for a local weekly newspaper.  i sent them a  
>> black
>> and white print.  looked like it did on my monitor.  but what  
>> about color?
>> i had done some business graphics for my nephew's business.  we  
>> made his
>> business card and had it printed, from a pdf (although not a  
>> scribus pdf)
>> and the colors came out like on my monitor.
>
> OK you think your monitor is now correctly calibrated but is it  
> really?  Since
> you are a Windows user (same is true for Mac users) you can shop  
> around and
> purchase a Pantone Huey for about $50 + shipping (look on ebay).   
> This device
> and the included software will allow you to calibrate and custom  
> profile your
> monitor(s).  I think you will be surprised at how much better all  
> of this
> works with a hardware calibrated and profiled monitor.   I know that I
> thought that my visually calibrated monitors were pretty close but  
> I was
> shocked at how much better they were after using a hardware  
> measurement
> device to calibrate and profile my monitors. For Windows and Mac  
> users the
> cost of getting the hardware and software to do this is now so low  
> that there
> is absolutely no reason for any Windows or Mac user who is doing color
> critical work to not have this type of device and software.
>
> One other point about hardware calibration.  Even with this  
> hardware and
> software to guide setting the monitor controls I can get the white  
> point to
> be very good with a delta E of less than 1.0 (very small error level)
> relative to D65 but at that setting my black point is off by a  
> delta E of
> about 16 (large error level).  Which means that my average delta E  
> along the
> black locus (the neutral tones) is about a 7 or 8.  At that point  
> the monitor
> is more neutral than I have ever been able to achieve using visual
> techniques.  Then running a hardware based calibration and loading  
> the video
> LUT with the resulting data corrects the black point problems and  
> results in
> an improved average delta E of around 1.0 with a peak of about  
> 3.0.  In
> addition the display gamma goes from 2.53 before LUT loading to  
> 2.24 (nearly
> perfect) after the LUT is loaded.   Overall the amount of  
> improvement in the
> display calibration and neutrality is striking.  Having used both  
> visual and
> hardware techniques for this I can tell you that with the low cost  
> of getting
> the hardware and software these days that I can no longer recommend  
> using
> visual techniques to anyone who is doing color critical work.
>
> When I do color critical work on Windows I use profiles provided by  
> my paper
> vendor for my printer.  In my case this is the Illford Galleria  
> Smooth Gloss
> paper profile for the Epson R2400.  The results are very good and  
> even more
> important totally predictable.  It might be possible to get  
> slightly better
> results with a custom printer profile since like all mechanical  
> devices these
> printers do have sample to sample variation.  In addition when I  
> send images
> out to printing services that have good color management work flows  
> the
> results I get back are an excellent match to what comes out of my  
> Epson
> printer and to what I see on my display.
>
> So for Windows and Mac users you can get setup to do input device  
> (scanners
> and cameras) profiling and hardware based monitor calibration and  
> profiling
> for less than $100.  You can also get free profiles from most paper  
> vendors
> for most currently produced color printers.  This will allow you to  
> setup an
> end to end color managed work flow that will give you consistent  
> totally
> predicable results.
>
> Hal
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