Mike Chaney's Tech Corner

Hello all,

I've printed out some targets using the job recall '{Q} printer target setup.job' but I wanted to know if it makes any difference to the print output if the check box in the colour management setting for image is set to on or off? The one that says 'honor exif color space tag where no icc profile is embedded', at the moment it is set to on with the default qimage sRGB.icm and this is what I used to print, when I unticked this box and tried selecting the printer target setup job it doesn't reset to any on or off position. I am very new to all of this colour management stuff, is an untagged tiff target sRGB anyway which would make this irrelevant.

I have just received a couple of custom profiles that were created from the targets I printed and although they are very good there is one particular block colour that I am unsure about which is why I am wondering about this setting, I am guessing that if there was any problem with the profile created then it would effect the whole image with a colour cast and not just one particular colour or tone. Anyway, probably too much info, just wanted to know if this exif setting makes any difference?

Thanks in advance.

sq

Hi sq,
When you use the {Q} printer target set up, it turns off printer colour management, a must for target printing. So what is set in the CM settings is turned off too.
Your Job properties (bottom right of main screen) should look like the attached screen shot - it's for QU but other versions of Qimage are the same.
Terry

Thanks Terry,

I understand that the printer colour management is turned off but does it also turn off the image colour management? What I mean is is that even with printer colour management turned off, if your print targets have a colour space embedded in them like Adobe RGB or whatever won't the colours be printed wrong or at least inaccurately to create a profile?

in edit/preferences/colour management/image imput if I have the 'honor exif colour space if no icc profile is embedded' set up wrong then won't qimage automatically assign the target a colour space before it goes to the uncolour managed printer? I thought that it was essential that the target image remained untagged.

Does that make sense?

thanks

sq

Hi sq,
Not necessarily but a target image should not have any profile exif data and no embedded profile either. I've checked the target images I have and that certainly applies.
In Qimage, you can tell there's an embedded profile by right mouse clicking with the cursor over the thumb, and selecting "display image info". It should say, <no embedded ICC profile>.
To check whether there is an exif tag, you'd need to use an exif reader like ExifToolGUI but if you have a target from a professional CM company, I'm sure there won't be one.
Terry

Ok, so to clarify, what you're saying is that with a professional target there will be no colour space or exif info embedded so if I've got this right...

qimage will see that there is no colour space so it will look for the exif data next. In a pro target there will be no exif data so qimage will leave the image unchanged as there will be no exif data to honor. So basically the image settings will be irrelevant as the outcome will be the same regardless off settings. Right?

On another note, but kind of related, when saving a file in photoshop with an embedded adobe rgb profile is this stored as exif data as I've noticed that the colour space line in properties is always blank (unless it's sRGB), always wondered where programs got this information from?

Thanks again Terry.

sq

Yes  :D
I'm not sure where you mean "the colour space line in properties", in Qimage-U or somewhere else?
The "Exif Hot Bar" under the thumbs in Qimage will default to sRGB if there's no embedded profile or exif data.
Are you sure PS does add exif data for Adobe RGB? It may "associate" a profile which  cannot read by other software but I'm not really sure?
There is no actual Exif standard for Adobe RGB like there is for sRGB; the exif data will say something like "uncalibrated". QU interprets this as Adobe RGB.
Terry.

That's brilliant, cheers Terry. And you're right about the properties saying uncalibrated for adobe rgb I remember now, my mistake. So qimage interprets uncalibrated as adobe rgb, that's good to know.

Thanks again, I'll stop hastling you now, you can go back to what you were doing. :D

sq

I thought it worked like this (and I wrote this not that long ago in another list):

Qimage has 3 main choices on color management:

1/ CM-Off = Qimage doesn't convert the file, sends the plain RGB data to
the driver so with the color space profile stripped from the file.

In that mode it will also not assign a colorspace to an untagged file,
for example a target file for profile creation. And Windows will not
assign a profile either, it leaves that task to applications.

2/ Let printer manage color = Qimage does the above but the color space
profile isn't stripped from the file so the printer driver CM can do
something sensible with the file.

3/ Qimage CM on, Qimage does the conversion and sends the converted data
to the printer driver, expecting that the last's CM is set to Let
application do CM, so in fact with the driver's CM off..

In both 2 and 3 Qimage could assign a colorspace to an untagged file
based on EXIF data, camera model as an educated guess or without any
hint available it will assign a color space, the default sRGB or a
preferred choice of the user, say AdobeRGB or nothing if the user
doesn't like guesswork.

The printer driver has usually two choices: let driver do CM and the
other one let application do CM.  With appication CM set the driver will
do no conversion at all and expects that the application does the work.
That is also the setting you will use to transfer targets through with
Qimage on CM off. When the driver does CM it will expect files with
certain colorspaces, my Z3200 can be set on AdobeRGB  or sRGB, the PS
driver has more spaces. The conversion happens to LUTs in the driver so
not with ICC profiles.

met vriendelijke groeten, Ernst Dinkla

Try: http://groups.yahoo.com/group/Wide_Inkjet_Printers/